Battery problem?

[Pedro_The_Swift]

From the limited pics, anyone guess why the batts show 12.9 most mornings,
3 x 200ah lithiums.

apart from two tellies, a sirroco fan or two and the odd LED light the only draw after sunset is the (brand new) Bushman fridge.
no inverters.

If I am reading the info correct it takes the system about 2.5 hours to recover to float ( according to Itech 13.5v)
They seem to lose 70% in 2 hours but then hold steady for the rest of the night...

[drivesafe]

Hi Pedro, that voltage is way too low for any lithium battery in good nick and with more that 20% capacity.

Can I make a suggestion.

Try running your system on one battery at a time.

The simplest way to do this is to remove the negative ( - ) lead from one battery and run everything off the other battery for a day or two.

Then take the negative ( - ) lead off that battery and reconnect the negative ( - ) lead back to the other battery and again, run your system of that battery and see what voltages you get.

I have been running a combination of a 100Ah lithium battery continually connected to a FAULTY cranking battery for well over two years and the lithium battery ( actually both batteries ) has never had a voltage reading below 13.15v.

NOTE only last week I replaced the cranking battery with a new one and have removed the lithium battery for testing.

[gavinwibrow]

Hi Pedro, that voltage is way too low for any lithium battery in good nick and with more that 20% capacity.

Can I make a suggestion.

Try running your system on one battery at a time.

The simplest way to do this is to remove the negative ( - ) lead from one battery and run everything off the other battery for a day or two.

Then take the negative ( - ) lead off that battery and reconnect the negative ( - ) lead back to the other battery and again, run your system of that battery and see what voltages you get.

I have been running a combination of a 100Ah lithium battery continually connected to a FAULTY cranking battery for well over two years and the lithium battery ( actually both batteries ) has never had a voltage reading below 13.15v.

NOTE only last week I replaced the cranking battery with a new one and have removed the lithium battery for testing.




Hi Tim - maybe leave that phone call you owe me until after Christmas (or new year even if you are still flat out)!

[Pedro_The_Swift]

Just to set the scene, I have two batts in the rear tunnel and one in the front.

I took the easy one first and disconnected the neg cable off the single batt last night just as the charge rate dropped to zero.
Batt reading of the system this morning was 12.6.
After reconnection it was 12.9

This is the rear tunnel situation,
the far right neg seems easiest,
I have to bolt the two neg cables (and others) together right?
I am ASSUMING the red you can see will be heatshrink.......

[Tins]

I am ASSUMING the red you can see will be heatshrink.......

Suck it and see. If it shrinks you'll have your answer[bigrolf]

[drivesafe]

I am ASSUMING the red you can see will be heatshrink.......
The RED heat shrink looks to be on the POSITIVE ( + ) Cables.

BTW The 12.6v reading is still way too low for lithium battery.

The 12.6v would indicate a very low ( below 20% ) lithium battery.

[Pedro_The_Swift]

Hmmm, there are lots of red power cables running off that right hand side battery... none of them will work after I take the neg cable off,,, right?

[drivesafe]

Hmmm, there are lots of red power cables running off that right hand side battery... none of them will work after I take the neg cable off,,, right?

Correct!

Unless there is a cable running from one battery's POSITIVE ( + ) to the other battery's POSITIVE ( + )

If this is the case, then you will still SAFELY isolate the battery you remove the NEGATIVE ( - ) cable from.

[Pedro_The_Swift]

So todays plan of attack is---

About to do some er carpentry? to get access to the terminals of the rear two.
This pic is of the arrangement of the cables, rather than try and move both batts outwards to get the terminals within arms reach
I' thought I'd go in from the top, under the lounge.

Anyway, my plan is, turn the caravan 12V off, pull the two neg leads off the batts, pull all the ACCESSORY POWER cables off the test batt and somehow add them to the other terminal, maybe a small "extension" cable? not much room under the gen batt bolts... bolt the two neg leads off the test batt together, bolt the neg lead back on the remaining array.

I hope this makes sense, I understand its Saturday, all opinions would be valued...

[Pedro_The_Swift]

I took the opertunity to check the other batts bolt tightness and the neg wasnt loose but needed a nip.. So, good!
The batt you can see has been disconnected, will let it charge all day and see if the voltage drops after sunset.. https://uploads.tapatalk-cdn.com/20221224/2ca7e5d7a242ca11544f22cc971e6107.jpg

[Pedro_The_Swift]

and the answer to that question is YES!
so the other side gets a hole,

I hope I'm just really unlucky----
and Third time IS a charm...

[Tins]

I hope this makes sense,

Good luck with that.

[Tins]

I hope I'm just really unlucky----


You get random strangers to remove light poles to help you out of a pickle.. How can you call yourself "unlucky"? No, wait, don't answer that..

[Pedro_The_Swift]

This pic with the last of three disconnected..

Doesnt fill me with good cheer at all,, WTF is going on??

[Graeme]

Faulty solar controller or faulty connections on the battery side of the controller?

I assume that the controller knows that the batteries are lithium.

[Pedro_The_Swift]

Yes,, number 7 on a really small rotary switch...

[Graeme]

The battery voltage is all over the place when the solar voltage is constant. I would select a different battery type, eg AGM, to see if the battery voltage is any more consistent.

[PhilipA]

Is it that the blocking diode in the solar panel or controller is not working ( or is not there!) , so the panel is taking back all the power from the batteries at night.
That is what happens with solar unless there are blocking diodes.
Regards PhilipA

Bypass Diodes & Blocking Diodes in Solar Panels | altE Solar Blog (altestore.com) (https://www.altestore.com/blog/2016/09/bypass-diodes-blocking-diodes-solar-panels/#.Y6gqH9VByUk)
To test , just disconnect your solar controller at night.
It looks from your voltage trace that the graphs are identical so this looks to be the problem.

[drivesafe]

Hi Pedro, do you have anything running off the battery while the solar is trying to charge it?

The solar voltage is fine except for the last section, where the voltage is all over the place and this could easily be caused by a load on the battery.

If you have no load on the battery, I would be looking at one of the batteries internal BMS.

[Graeme]

The last graph shows battery voltage dropping then rising for a short while then dropping again while solar voltage is constant, so not at night. Maybe the solar charger's lithuim support is incompatible with the battery's BMS, hence my suggestion to switch the solar regular to a regular battery that can take higher voltage.

[Pedro_The_Swift]

This is this mornings,
fridge is on, laptop charging from 700w Inverter, sleep apnoea machine working off battery.
Thats it. So not charging. But its not draining it as fast as after sunset.. the drop is probably the inverter kicking on.. the power brick for this laptop( GE 76 Raider) is 380W.

I still have Batt number 3 disconnected... no odd charging cycle with the other two unplugged..

[drivesafe]

Once again, unless that battery is in the final stage of discharge, the voltages are totally out of wake for a lithium battery.

Even a small lithium battery will hold at around 13.1v with a 30 amp load applied.

You have a much larger battery and a smaller load yet your battery voltage is all over the place.

Again, if it were my battery, I would be looking at the battery's internal BMS because lithium batteries do not behave like yours is.

[Pedro_The_Swift]

Being lithium I'm sure it has a BMS,,

can I access it??


No...


I put a meter on the connected batts this morning,( dont ask... ;( )
the Victron software was around ONE volt higher than the meter..

The cable running from the controller to the batts is the same from the roof panels to the controller( and NOT upgradable... no point the Victron wont accept bigger cable)
5mm external Dia..

cable run from controller to batts?
maybe 4m ??

waiting on Mitre10 to open, need longer M8 bolts on the batt terminals,

Bought a Victron BMV700, probably be 3 weeks before I can get it installed though...

[Tins]

Being lithium I'm sure it has a BMS,,

can I access it??


No...




Well, you can...


https://youtu.be/iNizQd-jTqg

[Pedro_The_Swift]

12.86 on meter, 14.2 on software..

[Pedro_The_Swift]

2 hours later and the batts are still at 12.86.
I dont think its charging at all..

[Pedro_The_Swift]

Fired up the Yamaha and put the charger on.. this in the middle of a sunny day..

[Pedro_The_Swift]

After 2 hours of Yamaha charge its up to 13.2 on the meter..

[drivesafe]

After 2 hours of Yamaha charge its up to 13.2 on the meter..
That’s an improvement.

Keep the charger on until the battery rises over 14.0v.

Anything under that and your battery will only be partially charged.

Also note, watch the charge and once the battery charging voltage is over 14.0v make sure the charge current drops below 1 amp before stopping the charge.

Depending on the type of charger, lithium batteries can site at say 13.6v for hours and then rise over 14.0v, but the battery will still be charging, until the current drops as stated above.

[W&KO]

Has the battery manufacturer offer technical support……..

Squinting at the pics are the batteries iTech World??

[josh.huber]

Being lithium I'm sure it has a BMS,,

can I access it??


No...


I put a meter on the connected batts this morning,( dont ask... ;( )
the Victron software was around ONE volt higher than the meter..

The cable running from the controller to the batts is the same from the roof panels to the controller( and NOT upgradable... no point the Victron wont accept bigger cable)
5mm external Dia..

cable run from controller to batts?
maybe 4m ??

waiting on Mitre10 to open, need longer M8 bolts on the batt terminals,

Bought a Victron BMV700, probably be 3 weeks before I can get it installed though...

What controller are you using?

While ever there is a difference especially that much in the controller to actual, there will be problems.

Test the voltage at night when there is no solar to see if there still is a difference in the voltages from actual the to softwate.

You can run bigger wiring, just bare it back at the connection. Or the better alternative to that .
Bring the wiring of it the controller just long enough to nearly terminate at a power stud. (Google Jay car power stud). Then run a set of wires to each of the batteries individually from there from at least 6mm.

[oka374]

The biggest problems I've noticed with wiring involving voltage drops is that the installers run cables that are too small for the distance and current required, or they run a nice big positive cable but a tiny little negative cable, or even worse connect the negative cable to a metal frame/chassis/whatever to avoid running negative cables at all!
The frame/chassis ground return is one of the biggest causes of grief due to dissimilar metals involved and corrosion of the connections.
The other source of grief is the fuseboxes that only connect the positive cables and provide nowhere for the negative cables to terminate. This results in ground/negative connections that are anything from bolt holding a lot of eye connectors or a tek screw into a piece of metal holding the eye terminals. I've even seen a van with the ground screw connection into a piece of wood!
A lot of these postive only fuseboxes also have a LED that comes on when the fuse is blown, what they don't tell you is that the circuit to light the LED also continues to carry current to the faulty appliance or wiring!

[Pedro_The_Swift]

Has the battery manufacturer offer technical support……..

Squinting at the pics are the batteries iTech World??

Yep, 3 x 200AH, and of course they have---
anytime after the 3rd of Jan...:bat:


checking at night is a great idea,, why didnt I read this last night..... oh yea flat batt in the laptop.. [bigrolf]



No fuses in this baby!! push button resettable breakers!!
I suppose at some stage today I will crawl under and look at cables, earth points and sizing.





12.9 at sparrow fart this morning

[Tins]

The biggest problems I've noticed with wiring involving voltage drops is that the installers run cables that are too small for the distance and current required, or they run a nice big positive cable but a tiny little negative cable, or even worse connect the negative cable to a metal frame/chassis/whatever to avoid running negative cables at all!


Not to mention the 'pretend' copper cables often used.

[trout1105]

Yep, 3 x 200AH, and of course they have---
anytime after the 3rd of Jan...:bat:


checking at night is a great idea,, why didnt I read this last night..... oh yea flat batt in the laptop.. [bigrolf]



No fuses in this baby!! push button resettable breakers!!
I suppose at some stage today I will crawl under and look at cables, earth points and sizing.





12.9 at sparrow fart this morning

Why are there no bootlace crimps on the MPPT controller connections?

[drivesafe]

Hi again Pedro and what is the current output of your battery charger and are you charging all 3 batteries at once?

Also where exactly is your battery monitor connected to your batteries?

[Pedro_The_Swift]

only 7 or 8 amps.. the charger will do double that,, but it needs to be plugged into a wall,,
The genny was only run for around 4 hours just on the rear two batts,

I just bought a Victron BMV 700, but its still in the box.

The solar controller is 5.2meters of cable away from two of the batts.

Batt Voltage now is 13.12.
Yield so far today is 1.04KWH

[RANDLOVER]

Why are there no bootlace crimps on the MPPT controller connections?

I'm guessing because Pedro prefers moccasins, or fluffy slippers if he is relaxing around camp.

[trout1105]

I'm guessing because Pedro prefers moccasins, or fluffy slippers if he is relaxing around camp.

I Always use bootlace crimps on those sort of terminations, it gives you a much better/securer connection [thumbsupbig]

[drivesafe]

only 7 or 8 amps.. the charger will do double that,, but it needs to be plugged into a wall,,
The genny was only run for around 4 hours just on the rear two batts,
At 7 or 8 amp, going how much you can draw down that brand of battery, you will need around 30 hours of constant charging, if the batteries were near the cut-out level.

[Pedro_The_Swift]

At 7 or 8 amp, going how much you can draw down that brand of battery, you will need around 30 hours of constant charging, if the batteries were near the cut-out level.

Yes Tim,, i understand just how long I need to use a generator to fully charge my batteries....
Not going to happen.

That was just an exercise/top-up..

if I get down to 12.5/6 then I'll do another 4 hours,,

Do you want a PIC of the people in this Park at the moment???

13.04 by the meter at 6.35pm
12.96 by software...

so its a bad cell??

or a bad controller??


2.32Kwh from the array today...

[PhilipA]

Have you tried disconnecting the solar controller from the batteries at night? I still think it is backfeeding to the panels.

Seeing the batteries took a charge from the generator there would appear to be nothing wrong with them.

BTW you can run a much bigger charger than direct from the 12v outlet from even a 1000w generator.

A 20amp 240Volt to 12volt charger will run no problems from a generator as long as it is sine wave , although I ran mine from even an old chugga.
Regards PhilipA

[Pedro_The_Swift]

Have you tried disconnecting the solar controller from the batteries at night? I still think it is backfeeding to the panels.


Seeing the batteries took a charge from the generator there would appear to be nothing wrong with them.

BTW you can run a much bigger charger than direct from the 12v outlet from even a 1000w generator.

A 20amp 240Volt to 12volt charger will run no problems from a generator as long as it is sine wave , although I ran mine from even an old chugga.
Regards PhilipA


There is an OFF option for the charger in the software, will try tonight

Reluctant to run genny....

The charger is set for "Low" (at the bottom) I think I did that the very first time overnight,,


Software showing over 14V at the battery,
Voltage at OUTPUT TERMINALS of controller showing a .5v difference
meter on batts showing 13.1 .. so we have a voltage loss of at least half a volt.


So far today its bulk charged for 3hours and 25 mins and gone to absorbsion

[Pedro_The_Swift]

14V at the controller output terminals,
13.17 at the batts.

will be the same at 6 tonight..........

[Graeme]

I wouldn't rely on the software and your meter voltages being comparable. I would use the meter to compare the voltage at the controller output and at the batteries when looking for voltage drop. Also check for voltage drop between the battery posts and the cable terminals, or better still to the cable wires if accessible rather than the terminals.

[PhilipA]

There is an OFF option for the charger in the software, will try tonight

I still suggest that you physically disconnect the controller from the batteries by unscrewing the positive terminal from the controller to the batteries.

You seem to be relying on the electronics working correctly but if they are not the test of where the problem lies is to physically isolate them.
Regards PhilipA

[Pedro_The_Swift]

Not so much relying as **** scared of blowing the controller up...[bighmmm]
big sparkies involved taking the positive away, even at night... maybe especially at night:eek2:

"Charger" turned off in the software menu...

Batt V on the meter is 13.05

Dont give up on me Phillip,,, as long as the batts get to 13V each day life goes on... [wink11]

We have tracked down a mobile sparky that MAY be able to visit us on the 3rd... maybe.

[josh.huber]

Not so much relying as **** scared of blowing the controller up...[bighmmm]
big sparkies involved taking the positive away, even at night... maybe especially at night:eek2:

"Charger" turned off in the software menu...

Batt V on the meter is 13.05

Dont give up on me Phillip,,, as long as the batts get to 13V each day life goes on... [wink11]

We have tracked down a mobile sparky that MAY be able to visit us on the 3rd... maybe.

Where are you Pedro? Did you go a few days without sun ? We have had some average weather here.

The difference between voltages is less.. Can you also check then at the terminals of the controller and compare them.. ie controller says 11v and you check at the terminals on it and report back..

[PhilipA]

Batt V on the meter is 13.05

That is very low and is less than 40% capacity.
If you unplug the positive to the controller from the panels first particularly at night, there should be no current. Then undo the positive to the batteries.
Regards PhilipA
182805

[Pedro_The_Swift]

There is a slight difference between software and terminal, varies between .01 and .1V.
and a difference between output terminals and batts of around half a volt, I can only assume the cable into and out of the controller is the maximum size,
6awg.


Batt Voltage this morning before reconnection- 12.88V



full sun for days,,

[drivesafe]

There is a slight difference between software and terminal, varies between .01 and .1V.
and a difference between output terminals and batts of around half a volt, I can only assume the cable into and out of the controller is the maximum size,
6awg.


Batt Voltage this morning before reconnection- 12.88V



full sun for days,,
Pedro, you need to check both the size of your cabling and the connections.

You should not be seeing 0.5v differences in voltage readings, unless you have undersized cabling and/or a high current discharge occurring.

If you have 6G cabling with good connections, and a short run between the reading points, you would need a discharge current of at least 100 amps to cause that sort of voltage difference.

Something is very wrong with your setup?

[Tins]

Pedro, you need to check both the size of your cabling and the connections.

You should not be seeing 0.5v differences in voltage readings, unless you have undersized cabling and/or a high current discharge occurring.

If you have 6G cabling with good connections, and a short run between the reading points, you would need a discharge current of at least 100 amps to cause that sort of voltage difference.

Something is very wrong with your setup?

I'm pretty much a novice here Tim, but could it be as simple as a bad joint? There certainly seems to be some untoward resistance causing that voltage drop. Or, as someone else mentioned, a poor earth return? KISS first?

[trout1105]

There is a slight difference between software and terminal, varies between .01 and .1V.
and a difference between output terminals and batts of around half a volt, I can only assume the cable into and out of the controller is the maximum size,
6awg.


Batt Voltage this morning before reconnection- 12.88V



full sun for days,,

This is why I asked about the lack of bootlace crips to terminate at the MPPT controller.
See the difference.
182838

[Tins]

This is why I asked about the lack of bootlace crips to terminate at the MPPT controller.
See the difference.
182838

For screw down terminals I couldn't agree more. Before bootlace crimps I used to solder the bared ends, although this can create its own problems, but it stopped the screw from spreading, and often cutting, the wire strands. Bootlace crimpers are cheap.

[Tins]

Oh yeah. In 2009 I had a major house fire. The cause? A bad joint behind a power point. Sure, 240V AC is different, but the principle is the same.

I know this isn't really related to Pedro's issue, but it's often the little things....

[Pedro_The_Swift]

This is why I asked about the lack of bootlace crips to terminate at the MPPT controller.
See the difference.
182838


Yes Thanks Trout...
Never seen one before...


at least two reasons why Crusader didnt use them--
They cost extra money
and
They cost time (money).

If you spent this amount of money on a new BMW Merc etc you would NEVER accept half the things that go on in new vans...

(maybe after bootlacing the crimp wouldnt fit in a 6awg hole anymore??)

[Tins]

[QUOTE=Pedro_The_Swift;3176318](maybe after bootlacing the crimp wouldnt fit in a 6awg hole anymore??)

Yes it would.

[Tins]

If you spent this amount of money on a new BMW Merc etc you would NEVER accept half the things that go on in new vans...



Off the rack vs bespoke.

[drivesafe]

I'm pretty much a novice here Tim, but could it be as simple as a bad joint? There certainly seems to be some untoward resistance causing that voltage drop. Or, as someone else mentioned, a poor earth return? KISS first?
Hi and Yes, it could be something that simple.

The problem is finding the cause in the first place and this is usually not that simple.

In Pedros case, I think he is going to have to do quite a bit of detective work before he resolves his issue or issues.

[Tins]

Hi and Yes, it could be something that simple.

The problem is finding the cause in the first place and this is usually not that simple.

In Pedros case, I think he is going to have to do quite a bit of detective work before he resolves his issue or issues.

Thanks. I guess going methodically over every joint and connector was how Pedro wanted to spend his holiday.

[Tins]

Thanks. I guess going methodically over every joint and connector was how Pedro wanted to spend his holiday.

And yes, Ron, I am aware of the tautology...

[trout1105]

Yes Thanks Trout...
Never seen one before...


at least two reasons why Crusader didnt use them--
They cost extra money
and
They cost time (money).

If you spent this amount of money on a new BMW Merc etc you would NEVER accept half the things that go on in new vans...

(maybe after bootlacing the crimp wouldnt fit in a 6awg hole anymore??)

These crimps are dirt cheap, they are faster to use than twisting the wire and struggling to feed it in the hole and Yes with the correct size crimp fitted it will easilly fit [thumbsupbig]

[PhilipA]

I guess That I haven't been clear on what I recommend.
The reason that I want Op to disconnect the solar panel and controller is that is is the beginning of troubleshooting systematically.
if the batteries stay up, great the solar panels or controller are the problem.
If not then next step is to disconnect all of the loads then add them back in one by one.
All the electronic doodads will tell you what is happening but not WHY. The why or identification of the problem can only really be done by systematically going through the inputs and loads to see where the problem lies and then addressing that issue.
Regards PhilipA

[Pedro_The_Swift]

Yes Phillip, I agree your way is simple and probably foolproof.



ATM the batts are losing maybe .25V overnight, I think thats pretty reasonable considering the accumulated draw of items.

While I'm not happy with the voltage drop theres little I can do except check the crimps.

will a bad crimp put a hard limit on volts transferred?
or just lose a ( if ever increasing) percentage?

I think ( and I know very little, hence why we are all here-- ;) ) the main problem is the seemingly hard limit the batts reach, around 13.1V that no amount of sunshine will increase. I dont think a bad crimp or voltage drop is the culprit..

The controller is putting out 14V and the batts are at 13.01


and just one more finger in the pie--
what would you trust more? a $500 Victron solar controller or an $11 multimeter..... [smilebigeye]

anyway its beer oclock...[bigwhistle]:rulez:

[drivesafe]

The controller is putting out 14V and the batts are at 13.01
That makes no sense.

You either have a very long cable run of thin wire between the solar controller and battery or you have a massive load.

Otherwise, you have some bad connections somewhere in your system.

A near one volt drop is a massive difference, and your batteries loosing 0.25v overnight is also unusual.

Lithium batteries, in good condition and state of charge, should have next to no loose of voltage over night, even with a good load applied.

BTW, if 13.1v is the highest voltage you see while charging a lithium battery, you are never going to fully charge it.

You need to maintain a charge voltage of at least 13.6v to 13.8v at the battery, to be able to fully charge a lithium battery and even then, at 13.6v, just like lead acid batteries, lithium batteries will take a very long time to reach a fully charged state.

[Tins]

Yes Phillip, I agree your way is simple and probably foolproof.


Which is probably why so few people follow it.






and just one more finger in the pie--
what would you trust more? a $500 Victron solar controller or an $11 multimeter..... [smilebigeye]

anyway its beer oclock...[bigwhistle]:rulez:

The multimeter. Far fewer things in the way. Difficult to test without a known voltage at hand though.

[Graeme]

When looking for the cause of a voltage drop the multimeter doesn't have to be particuarly accurate whereas using the same meter at both ends is very important.

An earlier picture suggests to me that the controller is in auto-detect mode. If this is true then best to set it specifically to lithium mode.

[josh.huber]

The cable run is long and because it's not reaching charge the load is high too.. so it's all bad on that front.

[PhilipA]

If you have a bad connection , crimp or whatever it will usually heat up and discolor the wiring around or even melt nearby plastic.

Regards PhilipA

[Tins]

If you have a bad connection , crimp or whatever it will usually heat up and discolor the wiring around or even melt nearby plastic.

Regards PhilipA

Hence my house fire.. But it's going to depend on how bad the joint is, and how long it's been bad, for that to show itself. Of course, a bad joint is only going to get worse.

[Pedro_The_Swift]

When looking for the cause of a voltage drop the multimeter doesn't have to be particuarly accurate whereas using the same meter at both ends is very important.

An earlier picture suggests to me that the controller is in auto-detect mode. If this is true then best to set it specifically to lithium mode.Has always been set to lithium...

[Pedro_The_Swift]

The cable run is long and because it's not reaching charge the load is high too.. so it's all bad on that front.Lets wait till the batts are load tested before I buy another controller, and run cable, inside a fibreglass composite caravan. ;)

[josh.huber]

Lets wait till the batts are load tested before I buy another controller, and run cable, inside a fibreglass composite caravan. ;)

Yeah 100% . It's worked correctly at some stage. I'm just saying the long run is always a cause. I've got my panel on the roof of my car and a victron controller. Only 130w and with 6mm automotive tinned cable. I get up to 0.7v drop to the battery. Nothing else I can do. Seems to loose it with a combo of heat. Fuse holders and circuit breakers.

[Tins]

Yeah 100% . It's worked correctly at some stage.

Has it though? What evidence is there of that? Serious questions.

[josh.huber]

Has it though? What evidence is there of that? Serious questions.

Very true, I wonder how many batteries it was originally sold with?

[Pedro_The_Swift]

Very true, I wonder how many batteries it was originally sold with?

Advertised with 2 100ah and two 170W panels, at the pickup point found just one of each... The dealer was most apologetic and asked what he could do... I asked for 3 new lead acids and they were promptly installed. Van was towed that night to Kingaroy where we stayed for 3 weeks. During that time those 3 batts were replaced with 2 x 200ah lithium Itechs, the controller was replaced with a 100/50 solarsmart mppt Victron and another 2 x 200w panels put on the roof. This setup was run until we reached Carnarvon where another Itech and another 170w panel were installed. Both installs were done by long established companies( not one guy and a ute..).


Just by coincidence, all this seems to have happened after our new fridge install, also since then the Truma LPG heater no longer works and neither does the LPG hot water......
I ASSUME its just some power cables not hooked back up, as I cant see how disconnecting something can lessen a charge... unless its an earth?

[Pedro_The_Swift]

Has it though? What evidence is there of that? Serious questions.


Kingaroy to Carnarvon is a long way... ;)

[Tins]

Kingaroy to Carnarvon is a long way... ;)

For a given definition of "long".

So, was it working properly in Kingaroy or do you just assume it was? If it was and it isn't now I'd be looking at something movement related, like a bad joint.

[Narangga]

Advertised with 2 100ah and two 170W panels, at the pickup point found just one of each... The dealer was most apologetic and asked what he could do... I asked for 3 new lead acids and they were promptly installed. Van was towed that night to Kingaroy where we stayed for 3 weeks. During that time those 3 batts were replaced with 2 x 200ah lithium Itechs, the controller was replaced with a 100/50 solarsmart mppt Victron and another 2 x 200w panels put on the roof. This setup was run until we reached Carnarvon where another Itech and another 170w panel were installed. Both installs were done by long established companies( not one guy and a ute..).


Just by coincidence, all this seems to have happened after our new fridge install, also since then the Truma LPG heater no longer works and neither does the LPG hot water......
I ASSUME its just some power cables not hooked back up, as I cant see how disconnecting something can lessen a charge... unless its an earth?

As we learn more of the ingredients of the soup - where and when did the fridge installation occur? I am assuming your assumption too...[wink11]

[Pedro_The_Swift]

195l Bushman installed in Perth.
Pic of rear of new fridge, should keep you guys busy for days.. [emoji1]
Auto lecky here at 7am...
Heater was just disconnected....https://uploads.tapatalk-cdn.com/20230102/d7a70975c9c9d49a29dfd6b9c525979d.jpg

[Hoges]

I've been following this thread fairly closely and am interested in the LiFePO4 ratings.
The 100AH LiFePO4 I bought from Jaycar about 12m ago,(hardly used but kept at about 80% State of charge) is connected to a Victron BMV712 "Smart Meter". I fully charged it today with a new Victron "IP65" 15A smart charger with a Lithium battery setting. It took several hours on "bulk" and gradually worked its way up to about 14V. After the absorption phase it went into float mode at 13.42V on the Victron meter and 13.45V on the IP65 charger output app. I disconnected the charger and let the battery 'rest' for 30 mins. The Victron meter is showing 13.39/13.40V both on the meter and the bluetooth app on the phone and 13.37V on two separate multimeters. This seems a significant difference from the 13.9V figure from DriveSafe.

I'm wondering if different BMS arrangements take account of the varying 'expected vs observed' voltages as experienced by Pedro?

[drivesafe]

The Victron meter is showing 13.39/13.40V both on the meter and the bluetooth app on the phone and 13.37V on two separate multimeters. This seems a significant difference from the 13.9V figure from DriveSafe.
Hi Hoges, the 13.9v I refer to is while the battery is being charged.

Your 13.39v RESTED voltage reading is fine and is normal for a good quality lithium battery in a fully charged state.

If you apply any load to that battery, it will drop to about 13.2v and stay at about that voltage until your battery is around 80% discharged.

At about 80% discharged, your battery voltage will start to drop.

[Hoges]

Hi Hoges, the 13.9v I refer to is while the battery is being charged.

Your 13.39v RESTED voltage reading is fine and is normal for a good quality lithium battery in a fully charged state.

If you apply any load to that battery, it will drop to about 13.2v and stay at about that voltage until your battery is around 80% discharged.

At about 80% discharged, your battery voltage will start to drop.

Ah! Thank you Tim. Ever the voice of reason and reassurance! [thumbsupbig]

[Tins]

I don't know if this is helpfull in context, but I'll leave it here and the viewer can decide:


https://youtu.be/0xOvINH4tKs

[drivesafe]

Hi Tin and while that guy may have had good intentions, he really has no idea what he was talking about.

He states that because his mate ( or whoever ) had used 10G cable instead of 6G cable, this would mean his battery would never fully charge

Completely wrong.

While the battery is in a low state of charge, yes it will draw the full 30 amps from the DC/DC charger and this 30 amp draw would cause the amount of voltage drop stated.

But as the battery got to around 70 to 80% charge state, the current the battery is drawing tapers off and as the current draw reduces so does the voltage drop.

So the battery will eventually be supplied will a low current charge at near the highest voltage being supplied by the DC/DC charger.

So with his limited knowledge of how batteries charge, if the battery needed that higher voltage to fully charge, it would be getting it.


Next, even at the reduced voltage, if this did not rise as the battery charged, the battery could still be fully charged with the lower voltage, it would just take a little longer.

All batteries can be fully charged with as little as 13.8v


Next, he calculated the voltage drop between the CRANKING battery and the DC/DC charger based on the cranking battery supplying the same current into the DC/DC device as that device was supplying to the AUXILIARY battery.


No DC/DC device works this way.

All DC/DC devices are inefficient and require far more current in than they can supply out to the battery being charged.

So his calculations are off by a considerable way.


If he knew this, he would have realised that what he was saying about having the charge device, be it a DC/DC charger or a solar charger, should mounted as close as possible to the battery being charged, was more important than he knew.

[Tins]

Hi Tin and while that guy may have had good intentions, he really has no idea what he was talking about.

He states that because his mate ( or whoever ) had used 10G cable instead of 6G cable, this would mean his battery would never fully charge

Completely wrong.

While the battery is in a low state of charge, yes it will draw the full 30 amps from the DC/DC charger and this 30 amp draw would cause the amount of voltage drop stated.

But as the battery got to around 70 to 80% charge state, the current the battery is drawing tapers off and as the current draw reduces so does the voltage drop.

So the battery will eventually be supplied will a low current charge at near the highest voltage being supplied by the DC/DC charger.

So with his limited knowledge of how batteries charge, if the battery needed that higher voltage to fully charge, it would be getting it.


Next, even at the reduced voltage, if this did not rise as the battery charged, the battery could still be fully charged with the lower voltage, it would just take a little longer.

All batteries can be fully charged with as little as 13.8v


Next, he calculated the voltage drop between the CRANKING battery and the DC/DC charger based on the cranking battery supplying the same current into the DC/DC device as that device was supplying to the AUXILIARY battery.


No DC/DC device works this way.

All DC/DC devices are inefficient and require far more current in than they can supply out to the battery being charged.

So his calculations are off by a considerable way.


If he knew this, he would have realised that what he was saying about having the charge device, be it a DC/DC charger or a solar charger, should mounted as close as possible to the battery being charged, was more important than he knew.

Thank you for that, Tim. Maybe he should have stayed a firefighter. And maybe YOU should have a YT channel!

I don't know DC/DC systems from nuclear physics, but I always thought the current in a system is on the load side, not the charging side.

I do know that I have a lot to learn.

[LuckyLes]

Thank you for that, Tim. Maybe he should have stayed a firefighter. And maybe YOU should have a YT channel!

I don't know DC/DC systems from nuclear physics, but I always thought the current in a system is on the load side, not the charging side.

I do know that I have a lot to learn.

The battery being charged is the load.

[Tins]

The battery being charged is the load.

Fair enough, but I was under the impression it would only draw what it could, unlike a fridge motor, for example. You can't trickle charge a motor.

Guess i need to read up on modern systems.

[drivesafe]

Thank you for that, Tim. Maybe he should have stayed a firefighter. And maybe YOU should have a YT channel!

If the manufacturers of the different products put up decent explanations of how their specific products work, it would go a long way to helping the average person both to understand how that product actually works and for people to make a far better choice when buying what ever they need.

Here are a couple of exanmples

Many people think that say if they have a 100Ah battery and they buy a 50 amp DC/DC deice and if that 100Ah battery is dead flat, the 50 amp DC/DC device will fully charge it in 2 hours.

The sellers of these devices just love that sort of misunderstanding, especially when the reality is that it will take at least 5 hours.

And the amount of times I see arguments about the required voltage needed when charging a battery.

Most read the chargers specs, where it states it chargers say an AGM battery at 14.7v and think this is the required voltage when in fact it is the maximum safe charging voltage and actually has nothing to do with a minimum charging voltage.

Another one I come across is the claim a DC/DC device with multi stage charging is a smart charging device while an alternator is a dumb charging device, yet even the old constant voltage type alternator is far superior at charging batteries that any DC/DC device on the market.

All this comes from clever advertising and not facts based info.

[Tins]

We've recently had some glaring examples of what can be achieved by marketing.

[Narangga]

195l Bushman installed in Perth.
Pic of rear of new fridge, should keep you guys busy for days.. [emoji1]
Auto lecky here at 7am...
Heater was just disconnected....https://uploads.tapatalk-cdn.com/20230102/d7a70975c9c9d49a29dfd6b9c525979d.jpg

So the outcome was that bad hey Pedro? [bigwhistle]

[Pedro_The_Swift]

Still waiting on iTech to weigh in..
Victron shunt installed. BMV700.

Shunt shows 98% changed with 12.9V

Anyone installed a victron shunt lately?
is there some secret switch to let it know its dealing with Lithium batts?

The Victron guy has seen the .CSV file from the controller and is happy with its performance.

[PhilipA]

The Victron guy has seen the .CSV file from the controller and is happy with its performance

I posted the battery charge percentages a few days ago. These apply to virtually all LiFePO4 batteries.
Resting charge should be 13.6-8 for a fully charged battery.

Regards PhilipA

[drivesafe]

I posted the battery charge percentages a few days ago. These apply to virtually all LiFePO4 batteries.
Resting charge should be 13.6-8 for a fully charged battery.

Regards PhilipA
I have a string of different lithium batteries, and I have never seen lithium batteries with a settled voltage that high. Maybe straight after a charger is removed, but normal settled voltage is 13.1v to 13.3v.

[Narangga]

I have a string of different lithium batteries, and I have never seen lithium batteries with a settled voltage that high. Maybe straight after a charger is removed, but normal settled voltage is 13.1v to 13.3v.

How many hours/days before you consider it settled Tim?

[Hoges]

Still waiting on iTech to weigh in..
Victron shunt installed. BMV700.

Shunt shows 98% changed with 12.9V

Anyone installed a victron shunt lately?
is there some secret switch to let it know its dealing with Lithium batts?

The Victron guy has seen the .CSV file from the controller and is happy with its performance.

I installed a Victron BMV712 which is v similar to the BMV700. I used the shunt supplied with the smart meter. The shunt itself is "agnostic" to the battery type.

Have you checked the "zero current" calibration and other settings?

There's a reasonably active Victron user community...this link might be useful
Initial Smart Shunt & MPPT Settings for Victron Lithium batteries - Victron Community (https://community.victronenergy.com/questions/61784/initial-smart-shunt-mppt-settings.html)

cheers

[Pedro_The_Swift]

I installed a Victron BMV712 which is v similar to the BMV700. I used the shunt supplied with the smart meter. The shunt itself is "agnostic" to the battery type.

Have you checked the "zero current" calibration and other settings?

There's a reasonably active Victron user community...this link might be useful
Initial Smart Shunt & MPPT Settings for Victron Lithium batteries - Victron Community (https://community.victronenergy.com/questions/61784/initial-smart-shunt-mppt-settings.html)

cheers


That link might be the ticket... Thanks Hoges!
I have been operating under the assumption the auto lecky changed ALL the necessary parameters in the shunt software--

but,, "Charged Voltage" by default is set at 13.2V
THAT link ^^^^^ says it should be 13.8.. Easy enough to change...
Also changed some other stuff, efficiency, some algorithm,
But isnt the controller supposed to work that voltage out??

[Hoges]

That link might be the ticket... Thanks Hoges!
I have been operating under the assumption the auto lecky changed ALL the necessary parameters in the shunt software--

but,, "Charged Voltage" by default is set at 13.2V
THAT link ^^^^^ says it should be 13.8.. Easy enough to change...
Also changed some other stuff, efficiency, some algorithm,
But isnt the controller supposed to work that voltage out??

Not quite ... the controller is "blind" to whether the system is lead acid or lithium. Thus, it requires instructions to operate accordingly.
Glad the link was useful! There's also a lot of instructions at "Youtube University"[bigrolf] on setting up the system.

[Pedro_The_Swift]

Anyone care to workout the voltage drop on a 6metre cable run of 13v at 20A using 6awg?
is 0.45v close?

[Tombie]

Anyone care to workout the voltage drop on a 6metre cable run of 13v at 20A using 6awg?
is 0.45v close?

Depending on the resistance of the Copper wire you have it would be around 0.34v

[drivesafe]

Anyone care to workout the voltage drop on a 6metre cable run of 13v at 20A using 6awg?
is 0.45v close?
Hi Pedro, the voltage drop is really an irrelevance in a battery charging circuit.

The fact you are using such thick cable means you will get a good charge at the batteries.

While the batteries are low, the voltage at the regulator will also be low because the battery draw current will pull the regulator voltage down.

Yes you could have as much as 0.45 while the batteries are charging, but the voltage drop is caused because the batteries are being charged at 20 amps and are pulling 20 amps, and this is regardless of the voltage.

As the batteries state of charge rises towards a fully charged level, the batteries themselves, will pull less current and this will mean the voltage drop between the regulator and the battery terminals will get smaller.

Again, because you have used such thick cable, you should have no problems fully charging your batteries, with the only limiting factor in your case, is how much time your have to charge the batteries.

[Hoges]

Anyone care to workout the voltage drop on a 6metre cable run of 13v at 20A using 6awg?
is 0.45v close?

Following on from Drivesafe's advice, for your "academic" interest however ,

check out Voltage Drop Calculator (https://www.rapidtables.com/calc/wire/voltage-drop-calculator.html)
Plugging in your Voltage and Current data, the calculated Vdrop is 0.312... which may well be different in "real world" for different resistivity of multi-strand wire and other factors... This table takes into account that you need to actually calculate the drop over 2 x 6m =12m... (for the return path)

[Narangga]

I posted the battery charge percentages a few days ago. These apply to virtually all LiFePO4 batteries.
Resting charge should be 13.6-8 for a fully charged battery.

Regards PhilipA


I have a string of different lithium batteries, and I have never seen lithium batteries with a settled voltage that high. Maybe straight after a charger is removed, but normal settled voltage is 13.1v to 13.3v.

I installed my 2 x 50Ah lithium batteries into the (Kimberley) camper trailer 8 months ago. I have always kept the Victron IP65 charger connected to them while the camper is not in use. The AGM's they replaced had a BM2 monitor attached so I attached that to the lithiums when I installed them.

I had not previously checked the settled voltage before. The Victron told me it was at Storage at 13.84V and the BM2 at 13.79 when I disconnected the power to the charger. That 0.05V discrepancy has been pretty consistent over the last 8 months since installation.

12 hours later the BM2 was reading 13.74.

24 hours later the BM2 was reading 13.69.

36 hours later (this morning) the BM2 is reading 13.65.

I know that the BM2 is not necessarily the most exact measurement tool in this instance but it certainly appears the voltage of my batteries is not dropping off a cliff even if the voltage is dropping slowly as they settle.

[Tins]

I installed my 2 x 50Ah lithium batteries into the (Kimberley) camper trailer 8 months ago. I have always kept the Victron IP65 charger connected to them while the camper is not in use. The AGM's they replaced had a BM2 monitor attached so I attached that to the lithiums when I installed them.

I had not previously checked the settled voltage before. The Victron told me it was at Storage at 13.84V and the BM2 at 13.79 when I disconnected the power to the charger. That 0.05V discrepancy has been pretty consistent over the last 8 months since installation.

12 hours later the BM2 was reading 13.74.

24 hours later the BM2 was reading 13.69.

36 hours later (this morning) the BM2 is reading 13.65.

I know that the BM2 is not necessarily the most exact measurement tool in this instance but it certainly appears the voltage of my batteries is not dropping off a cliff even if the voltage is dropping slowly as they settle.

OK, this is very much a "newbie" question. Does the controller/charger ( any, not just yours ) display the actual battery voltage, ie the potential difference between +ve and -ve posts, or does it display what the chip in the battery says it is?

[drivesafe]

I installed my 2 x 50Ah lithium batteries into the (Kimberley) camper trailer 8 months ago. I have always kept the Victron IP65 charger connected to them while the camper is not in use. The AGM's they replaced had a BM2 monitor attached so I attached that to the lithiums when I installed them.

I had not previously checked the settled voltage before. The Victron told me it was at Storage at 13.84V and the BM2 at 13.79 when I disconnected the power to the charger. That 0.05V discrepancy has been pretty consistent over the last 8 months since installation.

12 hours later the BM2 was reading 13.74.

24 hours later the BM2 was reading 13.69.

36 hours later (this morning) the BM2 is reading 13.65.

I know that the BM2 is not necessarily the most exact measurement tool in this instance but it certainly appears the voltage of my batteries is not dropping off a cliff even if the voltage is dropping slowly as they settle.
Hi Dale and sorry, I missed replying to your question.

I don't take to much notice of the "settled" voltage of any battery after they have been charged, regardless of what is used to charge them.

All batteries once fully charged properly, will have a surface voltage.

While lead acid batteries usually loose this surface charge a few hours after being charged, I have noticed that lithium batteries can hold a surface charge for many days.

In both cases, with either lead acid batteries and lithium batteries, applying a small load, will very quickly remove the surface charge and you will get a more accurate settlement voltage reading.

This is also why I have always recommended people ignore "OPEN CIRCUT" type voltage reading and make sure you have at least a small load applied to the battery for a short period of time before taking a voltage reading with any lead acid battery, while that load is still applied.

Back to the lithium voltage readings. I have two 100Ah lithium batteries, of the same brand and age and while one was last charged ( but not used ) 3 month ago, the other was charged and then removed from in my VW Tiguan two weeks ago, and both are sitting at 13.34, with no load applied.

Later on today, I will apply a small load to each of them and see what voltage they have then.

BTW, I find BM2 Bluetooth battery monitors have very accurate voltage readings.

[PhilipA]

I have a 100AH VoltX cheapy in my Caravan and after 4 months of non use and not charged it reads 13.27 volts through my simple amp, watt etc in line monitor. I have a master switch between the monitor and battery.

The battery has been connected when I wanted to test newly installed lights etc from time to time.

I note that after driving and charging through my Renolgy 20amp DC/DC charger it starts at about 13.8 resting then quickly drops to 13.6 then to 13.3 after say one night use for interior lighting and pump.(about 2-4AH).

I charge at max 14.4 for safety sake as the Renolgy has max volt options. The battery charges quite quickly doing that.
Regards PhilipA

[Pedro_The_Swift]

Finally got onto a Victron rep that had some common sense, ( the last wanted me to rewire the van and relocate the batts...) aparently Victron make a "Smart Battery Sense" that when attached to the batts talks to the controller via bluetooth and boosts the output to cover voltage drop..
Problem Solved.
Now I just to find one in WA..

[Hoges]

post deleted -applied to 24V or 48 V only..."mea culpa"[bighmmm]

[Tins]

post deleted -applied to 24V or 48 V only..."mea culpa"[bighmmm]

Dimittuntur tibi

[Hoges]

Dimittuntur tibi

[bigrolf]

[Narangga]

OK, this is very much a "newbie" question. Does the controller/charger ( any, not just yours ) display the actual battery voltage, ie the potential difference between +ve and -ve posts, or does it display what the chip in the battery says it is?

From one newbie to another - :spudnikwhat:

Hopefully someone will enlighten us. [biggrin]

[Narangga]

Hi Dale and sorry, I missed replying to your question.

I don't take to much notice of the "settled" voltage of any battery after they have been charged, regardless of what is used to charge them.

All batteries once fully charged properly, will have a surface voltage.

While lead acid batteries usually loose this surface charge a few hours after being charged, I have noticed that lithium batteries can hold a surface charge for many days.

In both cases, with either lead acid batteries and lithium batteries, applying a small load, will very quickly remove the surface charge and you will get a more accurate settlement voltage reading.

This is also why I have always recommended people ignore "OPEN CIRCUT" type voltage reading and make sure you have at least a small load applied to the battery for a short period of time before taking a voltage reading with any lead acid battery, while that load is still applied.

Back to the lithium voltage readings. I have two 100Ah lithium batteries, of the same brand and age and while one was last charged ( but not used ) 3 month ago, the other was charged and then removed from in my VW Tiguan two weeks ago, and both are sitting at 13.34, with no load applied.

Later on today, I will apply a small load to each of them and see what voltage they have then.

BTW, I find BM2 Bluetooth battery monitors have very accurate voltage readings.

Tim, I took you at your word and applied a 'small' (11w) load from a 12V fluoro light I had in the shed from my pre-LED days and let it run for a 'short' half an hour. The only other option is a portable Blue Tongue compressor as everything else is locked in the camper trailer under a cover to stop water ingress during a monsoonal Wet Season...

At commencement the reading was 13.65 & after the half hour was up it was 13.44.

22 hours later it is reading 13.43V.

[drivesafe]

Tim, I took you at your word and applied a 'small' (11w) load from a 12V fluoro light I had in the shed from my pre-LED days and let it run for a 'short' half an hour. The only other option is a portable Blue Tongue compressor as everything else is locked in the camper trailer under a cover to stop water ingress during a monsoonal Wet Season...

At commencement the reading was 13.65 & after the half hour was up it was 13.44.

22 hours later it is reading 12.43V.
Hi Dale, what is your battery’s Ah capacity?

[PhilipA]

22 hours later it is reading 12.43V.
You must have a considerable drain on the battery.
One thing forgotten is modern radios have an always live wire to the station memory, but this doesn't take much at all. But it will flatten a battery over a few weeks.
However you have a drain somewhere. if you have fuses take them all out, then replace them one by one until you see the voltage drop, or alternatively take out the fuses and put an amp meter across the fuse contacts.
That is why I have a master switch which isolates the battery from everything including the watt, amp, voltmeter which takes a little bit of power to run it.
Regards PhilipA

[Tins]

From one newbie to another - :spudnikwhat:

Hopefully someone will enlighten us. [biggrin]

Nope, the grown ups are ignoring us. Again.

[Narangga]

Hi Dale, what is your battery’s Ah capacity?

2 x 50Ah

[Narangga]

You must have a considerable drain on the battery.
One thing forgotten is modern radios have an always live wire to the station memory, but this doesn't take much at all. But it will flatten a battery over a few weeks.
However you have a drain somewhere. if you have fuses take them all out, then replace them one by one until you see the voltage drop, or alternatively take out the fuses and put an amp meter across the fuse contacts.
That is why I have a master switch which isolates the battery from everything including the watt, amp, voltmeter which takes a little bit of power to run it.
Regards PhilipA

After using the light for 30 mins the voltage read 13.44.

22 hours after the 13.44 reading the voltage read 13.43.

The batteries are in the camper trailer and there is no load on them as everything is switched off. There is no radio in the camper trailer.

[Narangga]

Nope, the grown ups are ignoring us. Again.

Well ignoring you anyway...[bigrolf]

[drivesafe]

After using the light for 30 mins the voltage read 13.44.

22 hours after the 13.44 reading the voltage read 13.43.

The batteries are in the camper trailer and there is no load on them as everything is switched off. There is no radio in the camper trailer.
I think you have a typo in reply #112 ????

[Tins]

Well ignoring you anyway...[bigrolf]

You forgot the voices in my head.

[Narangga]

I think you have a typo in reply #112 ????

Correct - 12.43 should read 13.43 and I will correct it now. Thanks.

[Narangga]

You forgot the voices in my head.

Mine were telling me I wasn't being ignored. [wink11]

[Hoges]

OK, this is very much a "newbie" question. Does the controller/charger ( any, not just yours ) display the actual battery voltage, ie the potential difference between +ve and -ve posts, or does it display what the chip in the battery says it is?

I'll venture that they're separate loads, between the +ve and -ve "posts". They each require a minimal current through a known resistor to obtain a reading. The Victron BMV712 smart meter for example is guaranteed to draw 1mA or 700mAH/month. The BMS must by implication, likewise draw minimal current given the long 'self discharge' times for LiFePO4 batteries. Within the order of accuracy for both, one might expect the respective readings to be within a few thousandths of a volt if both are operating correctly....

EDIT: Notwithstanding the above... I then realised that some fancy highend BMS setups have a bluetooth output...which draws current in its own right to add to the load, in which case the external controller might well utilise the BMS bluetooth signal to play traffic cop with the free flowing electrons[bighmmm]

In which case the answer to "does it display what the chip in the battery says it is" is akin to the question of the existance oe Schrodinger's cat.... maybe yes...or not...[bawl] (I hope this is a typical adult answer[bigrolf][bigrolf]

[Tins]

In which case the answer to "does it display what the chip in the battery says it is" is akin to the question of the existance oe Schrodinger's cat.... maybe yes...or not...[bawl] (I hope this is a typical adult answer[bigrolf][bigrolf]

"Typical", certainly. The jury is still out on "adult".

According to Sir Terry Pratchett, there was a third option for said cat: "bloody angry". Or perhaps, in my case, slightly frustrated.

[Pedro_The_Swift]

A short but sweet move to the Cricket Oval at Donnybrook...
connected my charger to the batts, set it at 15A and went to the pub...

After a freak storm that made us do an emergency awning take-down at 1am I checked the BMV and it was at 13.4V.. :woot:

At 7am the batts were in relatively full sun and over 14V.
Switched the charger off and its now showing 13.5..
:Thump::MileStone:

[drivesafe]

A short but sweet move to the Cricket Oval at Donnybrook...
connected my charger to the batts, set it at 15A and went to the pub...

After a freak storm that made us do an emergency awning take-down at 1am I checked the BMV and it was at 13.4V.. :woot:

At 7am the batts were in relatively full sun and over 14V.
Switched the charger off and its now showing 13.5..
:Thump::MileStone:

Hi Pedro, if you can, you should leave the charger on and let it go into FLOTE Mode.

This is when your batteries will actually be fully charged.

When the charging voltage is below 14+v, the charger is in BULK charge mode.

When the charge sits at a constant voltage of say 14.2v, this is the ABSORPTION Mode

The ABSORPTION Mode usually starts when the batteries are about 80 to 90% charged and continues charging the batteries until they are fully charged.

During the BULK charge stage, the charge current will be constant at your charger's 15 amps but the voltage will continue to rise up to where the charger goes into the ABSORPTION Mode.

In the ABSORPTION Mode, now the voltage remains constant and the current reduces as the batteries get closer to a fully charged state.

NOTE, in the ABSORPTION Mode, the batteries themselves control the amount of current being draw from the charger

Once the batteries draw less than about 1 amp, the charger will go into the FLOAT Mode and sit around 13.6 to 13.8v and then and only then will your batteries will then be fully charged.

The ABSORPTION stage of the charge can take quite a few hours but is necessary to achieve fully charged batteries.

[Pedro_The_Swift]

Thats tonights mission. Will switch it on at dusk and let it run till we de-camp tomorrow around 10ish..

[Narangga]

After using the light for 30 mins the voltage read 13.44.

22 hours after the 13.44 reading the voltage read 13.43.

The batteries are in the camper trailer and there is no load on them as everything is switched off. There is no radio in the camper trailer.

A week later the reading on the BM2 is 13.34V so still some 'settling' occurring.

[Pedro_The_Swift]

First part day with the Victron Battery sense connected...

Thats 706W's out of the array.. a 3.36KW day..
didnt get installed till 10 and theres an hour of sun still left...
Shunt says 13.36, controller still on bulk..

Mind you.. a wind generator might have made more today... :blink::blink::blink:

[Pedro_The_Swift]

Shunt now reading 14.2

[josh.huber]

This has been a great thread, battery sense is something that came in on alternators when I was an apprentice. After reading this I purchased a smart shunt IP65. It's IP Rated and lives under the bonnet, I have a similar mppt charger then you and was able to "link" the shunt to the charger thru the VE direct Bluetooth link. It's a great feature, wouldn't have known if I wasnt following this..

The Smart shunt also let's me monitor both battery's voltage and the dual batteries amperage, meaning I wouldn't need the bm2 units. Pretty handy to monitor the health of the second battery

[Pedro_The_Swift]

Up at Dawn this morning and shunt reads 13.26,,
I'm gunna call that a win.


Thank you all for your advice.. [thumbsupbig]



Just as an aside... all new vans are built with all the electronics right next to the batts..

and if this stuff interests you...
visit the Aust Victron facebook page..

Victron Users Australia (https://www.facebook.com/groups/1136089206821090)