D4's charging / battery problem

[surfingooner]

Where I only use my D4 at the weekends, my battery keeps getting flat. I replaced my battery about a year ago and I am now having same problem with a warning message coming up, when I turn the car off after use, and then the car won't start again.

I guess running the alarm and having a dash cam fitted, eat up the power during the week. So I bought one of those solar panels, that you plug into the lighter, which is supposed help, although my mate said they don’t work on all cars - do you happen to know if they work on LR s ?

I have a dual battery, but the stop start battery hasn’t worked for at least two years , which doesn’t really bother me, although I hadn’t considered if this might be a contributing factor, if anyone has had similar problems and knows what it might be, that would be hugely appreciated.

Cheers,

Matt.

[Tombie]

Where I only use my D4 at the weekends, my battery keeps getting flat. I replaced my battery about a year ago and I am now having same problem with a warning message coming up, when I turn the car off after use, and then the car won't start again.

I guess running the alarm and having a dash cam fitted, eat up the power during the week. So I bought one of those solar panels, that you plug into the lighter, which is supposed help, although my mate said they don’t work on all cars - do you happen to know if they work on LR s ?

I have a dual battery, but the stop start battery hasn’t worked for at least two years , which doesn’t really bother me, although I hadn’t considered if this might be a contributing factor, if anyone has had similar problems and knows what it might be, that would be hugely appreciated.

Cheers,

Matt.

The ciggie unit won’t work when the vehicle is off.

Did you reset the BMS when you replaced the main battery?

[theelms66]

The solar Will only work if your lighter plug has power with key off. Most vehicles these plugs are ignition controlled. Best to go directly to battery.

[INter674]

Mine has a brand new OE battery and the car will run it down v quickly to warning message stage eg with the ign on or stereo on for over 45 mins.

These are power hungry cars!!

[DiscoJeffster]

Mine has a brand new OE battery and the car will run it down v quickly to warning message stage eg with the ign on or stereo on for over 45 mins.

These are power hungry cars!!

I’ve had the ammeter on it sitting there not running and you can see peaks of 40amps being drained at times across all the electronics. You’re not wrong.

[scarry]

When the vehicle is off,make sure it is locked,thats when it uses the least power,and goes to 'sleep'.

Do you have the traxide dual battery system?

Ours is often left all week as well,i regularly charge the battery,or it gets to low.I hook the charger directly to the battery.

For the solar connection,a plug either at rear of vehicle or poking out the front grill maybe convenient,wired directly to the start battery.

[dukemasterpro]

When the vehicle is off,make sure it is locked,thats when it uses the least power,and goes to 'sleep'.

Do you have the traxide dual battery system?

Ours is often left all week as well,i regularly charge the battery,or it gets to low.I hook the charger directly to the battery.

For the solar connection,a plug either at rear of vehicle or poking out the front grill maybe convenient,wired directly to the start battery.

I had a low battery warning several times when camping at the weekend. We powered LED strip lights from the rear accessory point that’s always on - I think it’s connected to the Traxide system / aux battery not ignition like the front cigarette lighters.

The cranking battery is new ( less than year old ) and had driven 2 hours to the campsite.

The car still started a day later, short 15 min drive then again a few hours of camp lighting and phone charge that evening. Next day when opening the doors the Low Battery message comes on again.

So is the warning message just a spurious alarm ( ie just ignore it ) OR something to do with the car doors being open and shut sporadically ie the computers have not shut down completely.

Had left the Traxide switch in the “down” position. The camp lights always worked which was good and from the volt meter on my multiple usb and cig lighter adapter showing between 12v and 12.6 on the rear socket ( this is the aux battery? )

On the 2nd day the same volt meter was 11.9 before cranking the engine when it was plugged into the front cig lighter.

No further battery warnings when I got home after 100km drive.

I expect to get more warnings like OP’s if the car is parked and not driven for more than 2 weeks. Always have had this problem and when I’ve had the car in for service not had any issues reported.

With the Traxide system when away overseas I have plugged a charger in through the rear socket ( one on the left in the bumper ) with an adapter I got off disco3 forum. I think that has worked.

Overall just as puzzled by the Low battery message. Generally not been too concerned when it happens in your garage at home but if in the Outback or remote this would be a worry. That was the case a few years ago when I had the same Traxide system on my previous D4.

Not sure if the Aux battery would be good enough now to actually power a fridge? Being a 2014 yellow top. How can you check it’s strength?

[LRD414]

I had a low battery warning several times when camping at the weekend.
We powered LED strip lights from the rear accessory point that’s always on ....
..... day later, short 15 min drive then again a few hours of camp lighting and phone charge.....
Next day when opening the doors the Low Battery message comes on again.
Overall just as puzzled by the Low battery message.
This seems about right to me. When camping it's the opening of doors that really depletes the battery, in addition to the lights, fridge, etc.
The repeated waking of ECUs does it. We now have the habit of leaving one door ajar the whole time.

Plus if the starting SoC of your batteries was not 100% before you left you're already at a disadvantage.
For example if the SoC is say 75-80% the BMS will not top this up much, if it all. This is based on monitoring live values for a few weeks.
Then you get to camp, run fridge, run lights, open doors a few times, etc, etc.
The 15 minute drive doesn't help at all, probably makes it slightly worse if anything.
Starting the car loses depletes the battery and 15min is barely enough to get it back.
A portable solar panel is the go if stopped for more than 2 days, and fully charging batteries before the trip.


Not sure if the Aux battery would be good enough now to actually power a fridge? Being a 2014 yellow top. How can you check it’s strength?
A 2014 Optima would be right at the limit of its typical life based on what I've experienced and quite a few other D4 owners I know.
It's likely to be well down on the 55ah nameplate. If so this would further hamper your situation.

You'd need to have it tested at a battery place to confirm but I don't think there's too many with 2014 yellowtops still going.

Regards,
Scott

[dukemasterpro]

This seems about right to me. When camping it's the opening of doors that really depletes the battery, in addition to the lights, fridge, etc.
The repeated waking of ECUs does it. We now have the habit of leaving one door ajar the whole time.

Plus if the starting SoC of your batteries was not 100% before you left you're already at a disadvantage.
For example if the SoC is say 75-80% the BMS will not top this up much, if it all. This is based on monitoring live values for a few weeks.
Then you get to camp, run fridge, run lights, open doors a few times, etc, etc.
The 15 minute drive doesn't help at all, probably makes it slightly worse if anything.
Starting the car loses depletes the battery and 15min is barely enough to get it back.
A portable solar panel is the go if stopped for more than 2 days, and fully charging batteries before the trip.


A 2014 Optima would be right at the limit of its typical life based on what I've experienced and quite a few other D4 owners I know.
It's likely to be well down on the 55ah nameplate. If so this would further hamper your situation.

You'd need to have it tested at a battery place to confirm but I don't think there's too many with 2014 yellowtops still going.

Regards,
Scott

I had the yellow top fitted as backup for the winch previously so I guess that was the priority then. Maybe now with a fridge purchase in mind I need to replace that battery with something more up to the task. The last time I had borrowed a fridge we also had solar panel connected to the Traxide Anderson plug. From memory it was ok, fridge and lights ran but the as per this recent trip the dashboard Low Battery Warning.

Will keep a door propped open next trip if that’s the best practice. I did actually think about bringing the ctek along as we were at a powered site. Next time!

[Ferret]

...For example if the SoC is say 75-80% the BMS will not top this up much, if it all.

My experience also after monitoring its behaviour. Once it gets above 80% it just losses a bit of interest in charging it further. It will get to 100% but only after hours of driving.

[Turtle60]

Definatly agree yellow top is most likely draining your start battery. I suggest you Disconnect the yellow top for a week, charge your main battery, and see If you still get the low battery message over the course of the week. If it’s dodgy the cable size would suck the life out of it real quick. You could have them load tested but they are designed to sell batteries after all
also there’s the whole how many times do u stop / start etc doing short runs.
What is your replacement battery? If it’s not a decent AGM it will probably be very marginal already especially with multiple low battery messages. Local indie says inrush of power ultimately buckles the plates pretty quick on anything but quality AGM’s. Yes they are costly but flat batteries are a pain.
I might be lucky but mine sits for 8 days a fortnight and I don’t get this message. Got 5 years on original battery. And I do plenty of short runs ( Bunnings is less than 1 klm away).

[drivesafe]

My experience also after monitoring its behaviour. Once it gets above 80% it just losses a bit of interest in charging it further. It will get to 100% but only after hours of driving.
Hi Ferret, this is actually quite normal charging.

The last 20% of the charging cycle is controlled by the battery, not the charging source. It is usually termed the ABSORPTION stage of the charge.

The condition of the battery will also have an effect the charging of any lead acid battery. If a battery is in a poor condition, it will take longer to charge.

I'll cover this more in my next reply.

[drivesafe]

A couple of points to cover here.


First off, the “Low Battery, Start Motor” message is usually supplied by your infotainment unit, and in many cases, when this message is displayed, you will usually have some form of limited operation of the entertainment system, like a dramatic reduction of the volume.


The warning is usually at battery voltage levels of 12.2v or lower.


Your motor can be stated at 11.6v ( 20% SoC ) so you will normally still have plenty in reserve.


As in my last reply, the final stage of charging is controlled by the battery and if the battery is in a poor condition, it will not only take longer to fully charge but you will most likely have a reduced total usable capacity.


This is commonly caused by lots of short drives and no maintenance charging before you go on your trip.


A good practice to get into is to carry out an over night charge, every night for up to a week before you go on a trip.


This type of maintenance charging will both increase the amount of battery capacity you will have when you need it and will get the batteries back to a better condition.


The additional advantage of this is that if you stop in one place for a while and use a fair bit of battery capacity when you move to your next stop-over, because your batteries are in good condition, you will replace far more used capacity in a shorter drive time.


There is a lot more to this, but some basic maintenance charging has some good benefits.

[Ferret]

Hi Ferret, this is actually quite normal charging.

The last 20% of the charging cycle is controlled by the battery, not the charging source. It is usually termed the ABSORPTION stage of the charge.

Yes I'm aware charging current is controlled by the battery state but what I'm saying is, at times the BMS seems to not want to maximise the SOC.

For instance, I see it at times drawing from the battery rather than charging the battery when SOC > 80%, ie it only tries to charge the battery when coasting or under brakes. So at times, it is not a simple absorption stage, it's doing something else during this phase - monitoring / testing, I don't know what. Point is, the BMS sometimes shows little interest in getting the battery to the max SOC possible until the duration of whatever is going on in that phase finishes.

I have posted this picture before showing current draw from the battery while driving. I thought at the time it was associated with fitting a new battery or maybe resetting the battery with the GAP tool but since I have become aware of it and look I have noticed it doing it periodically. And as stated above, that battery draw reverses to a battery charge when braking or coasting which means effectively there is no net change in SOC, even after driving for a while.

Might be just some weirdness with my vehicle but it happens.

[drivesafe]

Hi again Ferret, and the reading you see in your screen snap is of a battery that is near fully charged and the vehicle is drawing on the cranking battery to reducing the load on the alternator while you have your foot on the accelerator peddle.

This is called Kinetic Charging and if you have a look at the link below, I describe it in more detail.

Again, your screen snap is of a battery that is near fully charged. If your vehicle has one of my isolators fitted and if you have been camping for a day or two and have been drawing on your cranking battery, when you start driving again, your vehicle's BMS will monitor the cranking battery as you start your motor.

In this case, as the cranking battery is not at a fully charged state, the BMS will disregard the Kinetic operation and just runs the alternator at 14.v until the BMS ascertains that the cranking battery is at a near fully charged state again.

The BMS only controls the VOLTAGE level of the alternator and current output of the alternator is dependant on the current load being applied to it.

So in vehicles fitted with my isolators, where the cranking battery is used to assist the auxiliary battery, if the cranking battery is anything but near fully charged, while the alternator voltage is held high to charge the cranking battery, all batteries connected to the alternator, including batteries in a camper trailer or caravan, will all be receiving a charge.

Again, there is a lot more to it and I will be adding to the thread below, shortly.

On-Line auto electrical info (https://www.aulro.com/afvb/the-verandah/246755-line-auto-electrical-info-9.html)

[Ferret]

...This is called Kinetic Charging

Yes accept all that.

The problem is the BMS does not know you have a fridge full of food in the back nor that you are going way and ideally want to arrive at your camp site several hours later in a higher SOC than what you initially set out with. On long trips along flat roads there is less opportunity to be coasting under brakes or going downhill so that type of charging behaviour just tends to draw down your battery till it drops to whatever SOC (or other conditions are reached) which kicks it out of that type of charging behaviour and the BMS resumes normal service.

And I might add, it does not behave that way all the time. Sometimes, even when at a high initial SOC, The BMS does not display that kinetic charging behaviour, it just displays a normal 'adsorption' type charging behaviour and the battery eventually reaches 100% SOC.

I guess I would rather it concentrated on just charging the battery rather than saving me some fuel.

[Tombie]

You know it’s not allowed to though - all done to meet emissions.

[Ferret]

You know it’s not allowed to though - all done to meet emissions.

There should be a law against hot beer.

[drivesafe]

Hi again Ferret, I must be missing something, why is your fridge not working?

[Ferret]

Hi again Ferret, I must be missing something, why is your fridge not working?

Nothing wrong with the fridge. Just bitching about a BMS which decides sometimes you really don't need your batteries being charged even though you might be needing all the charge you can get cause you are expecting to be powering a fridge at a campsite later that evening. .

[drivesafe]

Hi again Ferret, I would like to see voltage data logged over a trip, to see exactly what is going on in your vehicle.

You can not drive for very long with a 13 amp draw on your cranking battery without it dropping below that theoretical 80%. Even with a battery at 100%, you would only need to drive for a little over 20 minutes with that type of draw, before you battery was under 80% SoC.

Your screen snap is just a momentary look at what is happening and gives no info relating to what actually occurs over a whole trip.

While I use to monitor current in and out of a battery as an indication of charge capability of a given system, but over the last few years I have changed the way I determine battery capacity.

I now put more credence in what I can actually draw from a battery using controlled discharge loads applied to a battery or system.

This is a very slow process but is proving to be far more accurate and closer to real world usage.

[LRD414]

.... it does not behave that way all the time. Sometimes, even when at a high initial SOC, The BMS does not display that kinetic charging behaviour, it just displays a normal 'adsorption' type charging behaviour and the battery eventually reaches 100% SOC.
My experience matches yours pretty well Ferret, although getting beyond 90% is very rare.
Whatever is going on, the BMS cannot be trusted to get the batteries beyond about 85% SoC on any given drive (even a long one).

Cheers,
Scott

[drivesafe]

I’m going to throw a spanner in the works.

How do you know the battery is not being charged beyond 80-85%?

What are you using as a reference?

[Ferret]

I’m going to throw a spanner in the works.

How do you know the battery is not being charged beyond 80-85%?

What are you using as a reference?

The SOC as reported by the BMS system to the GAP tool. How the BMS arrives at the reported SOC though is a mystery, as is the algorithm which drives it's charging behaviour.

[drivesafe]

The SOC as reported by the BMS system to the GAP tool. How the BMS arrives at the reported SOC though is a mystery, as is the algorithm which drives it's charging behaviour.
Again, without data logging the operating voltage over the whole trip, those momentary readings don’t really indicate what is happening in the way of overall charging of the batteries.

Not that sure of the accuracy of the readout either. I remember seeing a readout posted up for a D4 a while back and it was showing the alternator current as being 220 amps.

Correct me if this is wrong, but a D4 has a 180 amp alternator?

[Stuart02]

Had left the Traxide switch in the “down” position.


By "down" do you mean toward or away from the LED? I can't remember offhand which is for normal v winch but if you put the battery in for winch backup it might be set wrong? I'm guessing you had someone else do the traxide install?

Running a medium fridge and a few light strips for a couple of days should be nothing to the yellow top. My 2010 Sport does that after nothing but 4km commutes for months at a time (do you think SWMBO will catch a train?!?) and just a couple of hours drive to camp.

I do leave the tail gate up while around camp.

I consider the traxide the single most important upgrade for these cars both for going bush and city life. I don't know how the Toorak tractors survive, tbh. First time I had the footy on the car radio I drained the battery to warning level.

[drivesafe]

Where I only use my D4 at the weekends, my battery keeps getting flat. I replaced my battery about a year ago and I am now having same problem with a warning message coming up, when I turn the car off after use, and then the car won't start again.

Matt.
Hi Matt, can you give me a call, today or over the weekend and if you have a multi meter available, I can talk you through some tests.


In the last month I have had to very strange faults located. One in a D5 and one in a D4.


Both faults related to the auxiliary battery not charging properly while driving, and in the case of the D4, the fridge would only run for a few hours before the low voltage shut it down.


In both cases, the initial feedback sounded like a bad connection and most likely a bad earth connection.


In both cases, with the motor running, the D5 had 14.7v across the cranking battery terminals, and the D4 had 13.8v across the cranking battery terminals.


But both auxiliary batteries were only at, or getting 12.8v to 12.4v across the auxiliary battery terminals.


After quite a bit of testing by the owner of the D5, we found a very strange fault.


When measuring the voltage across the cranking battery terminals, the voltage was 14.7v.


When measuring the voltage from the cranking battery’s positive ( + ) terminal to an earth point, the voltage was 14.7v.


When measuring the voltage from the cranking battery’s negative ( - ) terminal to an earth point, there was a the voltage 1.8v reading where the reading should have been 0v or very close to it.


The D4, tested last Monday, had a voltage difference of 1.4v when measuring from the cranking battery’s negative ( - ) terminal to an earth point.


So Matt, or anybody else interested in some testing of their setup, can you call on 07 5569 2557, day or evening.


While my L322 RR does not have a problem with earth points, I have had a couple of L322 customers who did have an earthing problem, but the bad earth was found to be caused by paint on the nut, on the rear bumper stud. With the paint removed, the problem was solved.

[Ferret]

So here is a log of a 35 min drive. The battery has been initially charged via a battery charger to SOC 96%, according the GAP tool.

Whist driving and maintaining a relatively fixed speed the BMS allows the battery to be drained, note the long periods of negative battery current. Only under brakes or coasting is the alternator charging the battery. The strategy drains the battery, at the end of the drive the battery SOC is 88%.
155826

[drivesafe]

Thanks Ferret for the graph, but as I posted earlier, SoC readings are meaningless.

The SoC of any battery is determined by the battery’s condition at the time the reading is taken, and an instantaneous reading will give no genuine idea of the battery’s actual charge capacity.

While a voltage reading fulls into the same spurious results, but a voltage reading, when two or more batteries are connected to the alternator, gives a much more detailed indication of what is happening in the whole system, not just at the cranking battery.

I’ll post up some graphs shortly, showing what I mean.

[Ferret]

To clarify, there is two batteries. And whether the reported SOC is correct or not, if the alternator is not putting out any current then the entire power to run the vehicle is coming from the battery and the alternator is more off than on.

But anyway, lets wait till you explain further.

[drivesafe]

To clarify, there is two batteries. And whether the reported SOC is correct or not, if the alterator is not putting out any current then the entire power to run the vehicle is coming from the battery and the alternator is more off than on.
Hi Fettet and again, the graph just does not show enough info.


SoC is a guesstimate, and when the alternator is charging, where is the charge going.


You vehicle will be drawing somewhere around 40 amps ( day time ) to 50+ ( night time ) then there are two or more batteries drawing charge.


But at the end of the day, the amount of energy available comes down to what is actually in the batteries.


All cranking batteries are high current charging batteries, and so are batteries like Opima and Odyssey batteries.


These batteries will tolerate very high currents and this means that even short bursts while driving, will quickly recharge these types of batteries and yes, not likely to be to 100%.


The graph is nice to look at but tells you nothing about what is actually in your batteries.


The only way to get an accurate indication of what’s available, is to actually use the battery capacity and see what you end up with.


A few months back, after few charge/discharge cycles, to see what was available, using a 4 amp load applied to a DT90’s ACCESSORIES output, I discharged the cranking battery down to 12.02v and the Optima down to 11.53v.


After letting the batteries settle overnight, I then went for a 33 minute drive. I deliberately drove for as close to 30 minutes because my RR, and D3s have a 30 minute charge cycle before they settle on a “Cruise” voltage.


On getting back from the drive, I let the batteries settle for two hours and then carried out another 4 amp discharge cycle.


With both batteries discharged down to the same levels, I had drawn 45.6Ah from the two batteries.


A few minutes after the start of the discharge cycle, the the cranking battery was at 12.67v and the auxiliary battery was at 12.64v.


If your were to use an SoC table, the two batteries were THEORETICALLY well over 95%. They were actually around 75 to 80%


That is just too much of an error margin.

[dukemasterpro]

By "down" do you mean toward or away from the LED? I can't remember offhand which is for normal v winch but if you put the battery in for winch backup it might be set wrong? I'm guessing you had someone else do the traxide install?

Running a medium fridge and a few light strips for a couple of days should be nothing to the yellow top. My 2010 Sport does that after nothing but 4km commutes for months at a time (do you think SWMBO will catch a train?!?) and just a couple of hours drive to camp.

I do leave the tail gate up while around camp.

I consider the traxide the single most important upgrade for these cars both for going bush and city life. I don't know how the Toorak tractors survive, tbh. First time I had the footy on the car radio I drained the battery to warning level.

https://uploads.tapatalk-cdn.com/20191123/9dcabf964097a38542cb72781366b456.jpg

Like this - that’s in the “down” position? The way it was installed in the current vehicle and at a guess the previous vehicle with winch. Used the same guy to install both times.

[LRD414]

SoC is a guesstimate, and when the alternator is charging, where is the charge going
The graph shows battery current and alternator current, so it does indicate where the charge is going. The difference between the values is going to vehicle systems, lights, etc. The BMS controls how much is available to go to the battery so needs to know alternator output and current going to/from battery, which can be displayed.

Ferret‘s experience is similar to mine. We may not have all the technical details exactly correct but I think it’s clear that the charging regime of a D4 does not promote “full” or “approaching full” batteries whether you have a dual setup or not. It does a good job if you’ve run the batteries down to a low SoC by subsequently getting the batteries up to a reasonable level quickly but you don’t get full even when driving all day.

I agree the accuracy of displayed SoC figures coming from the BMS via diagnostic tool can be questioned especially when there’s a dual battery setup, ie how the BMS calculates SoC is unknown. But the relative performance seems to be realistic.

I have charged overnight for a whole week and had the BMS SoC reading (via iiD) up at high 90s and occasionally 100%, as you’d expect. But daily commuting without overnight charging it tends to sit at 80-85% for good condition new’ish batteries and sometimes, especially with repeated short drives, it’s left as low as 70% before increasing the alternator output enough so that there’s any going to the battery. This also makes sense given that, as you’ve said, the last 20% of capacity is controlled by the battery, which takes longer and won’t happen with shorter drives. And then when I’ve been camping the SoC indicates lower figures generally in line with what I’d expect for my overnight usage.

So I think the SoC readout is accurate enough to assess what the BMS is doing in an overall and relative sense. It seems that the system just wants the battery to be between 70 and 85% and is not interested in anything else. I wish it was programmed to periodically charge the battery up to full or at least close. And I also wish it didn’t wake up all the ECUs when you open any door, why not just the drivers door, even that would be a big help when camping.

Scott

[Markus1]

Imo something to be aware of is that anything but a professional multimeter will read anywhere up to 0.15v wrong at 12v. Between my cheap meter and my mates Fluke, on a cold day there was 0.2v difference. I thought I had a bung meter until I read its specs on accuracy.

I've also noticed that even a 0.3amp draw E.g door open is enough to pull an aging battery (e.g 3 years old) down 0.1-0.15v. Presumably this is an issue of surface charge depletion as recovery is very fast.

I believe all this can all add up to give quite eroneous readings at 12v unless you really know what your doing.

[drivesafe]

So I think the SoC readout is accurate enough to assess what the BMS is doing in an overall and relative sense. It seems that the system just wants the battery to be between 70 and 85% and is not interested in anything else. I wish it was programmed to periodically charge the battery up to full or at least close. And I also wish it didn’t wake up all the ECUs when you open any door, why not just the drivers door, even that would be a big help when camping.

Scott
Hi Scott, and again, while the vehicle’s BMS has access to a large number of factors, to be able to come up with an SoC reading, this does not give a real idea of what’s going on.


The only way to know if the vehicle is even attempting to charge batteries, primarily the cranking battery, is to have a voltage reading.


In each of the ALTERNATOR spikes in Ferrets graph, I’ll lay money that the voltage goes to 14.7v every time. At this voltage level, the batteries will be taking heaps of charge.


And as posted, short of doing a controlled discharge test, there is no way of knowing just how accurate, or inaccurate those SoC readings are.

[Ferret]

In each of the ALTERNATOR spikes in Ferrets graph, I’ll lay money that the voltage goes to 14.7v every time. At this voltage level, the batteries will be taking heaps of charge.

Yes it does go to 14.7v, you can see the battery voltage increase and you can see the battery draws ~50+ amps before rapidly falling from those peaks even when the voltage is held at 14.7v But all that (the alternator spikes) only happens because you are braking or coasting. That is, the battery is being charged only because of opportunistic reasons related to traffic flow or road layout.

What happens when you are not city driving, instead driving along flat deserted country roads where little to no braking / coasting is required? - Your battery is depleted to some lower state of charge. It doesn't matter if you can measure SOC accurately or not - if your not charging because there is little need to brake / coast your net SOC is most likely falling.

Anyway, I'll send you the data and you can paw over it.

[drivesafe]

What happens when you are not city driving, instead driving along flat deserted country roads where little to no braking / coasting is required? - Your battery is depleted to some lower state of charge. It doesn't matter if you can measure SOC accurately or not - if your not charging because there is little need to brake / coast your net SOC is most likely falling.
This is where the voltage readings are needed.


Your alternator can operate down to 12.7v and not draw on your batteries.


It’s only if the voltage drops below 12,7v that the cranking battery will start to compensate for the lack of alternator power.


BTW, your use of the brakes has no effect on the alternator voltage rising.


As you have stated, when coasting the voltage rises.


When coasting, the accelerator peddle is not being pressed, as is also the case when braking.


If the accelerator peddle is not pressed, then the kinetic energy of the vehicle is used to power the alternator at high voltage ( 14.7v ).

[Ferret]

This is where the voltage readings are needed.

What relevant voltage reading are you not seeing on that chart.

[drivesafe]

Hi Ferret, that is nothing more than a line on a page, it gives no actual voltage reading, just a line on a page.

[Milton477]

Here you are Drivesafe

155851

That was after a warning to start the car. I had 2 Optimas i circuit + the cranking battery. Were the Optimas taking 50A each?

You should see what having a DC2DC charger does to the charging circuit when the batteries are down a bit. Current cycles between 50A & 200A continuously. I have now added a remote control to enable me to disconnect the 12V from the D4 to the DC2DC until the D4 batteries are charged up a bit.

When somebody figures how the D4 BMS works, please let us into the secrets.

[DiscoJeffster]

Ferret, I’m with you. Post the CSV of the data. I’ve seen similar. Stupid car love to deplete the battery. It probably explains why these vehicles only get 3 odd years from a battery yet others get twice that on average. My Audi got 11 years out of its! It also explains why people endlessly tell you to put it on a charger monthly if you want the battery to survive. No other car I’ve owned needed this level of attention for its battery.

[drivesafe]

Here you are Drivesafe

155851

That was after a warning to start the car. I had 2 Optimas i circuit + the cranking battery. Were the Optimas taking 50A each?

You should see what having a DC2DC charger does to the charging circuit when the batteries are down a bit. Current cycles between 50A & 200A continuously. I have now added a remote control to enable me to disconnect the 12V from the D4 to the DC2DC until the D4 batteries are charged up a bit.

When somebody figures how the D4 BMS works, please let us into the secrets.
EDIT READ Milton ( sorry Ferret ), what size alternator have you got on your D4.

Also, you should not have to disconnect your DC/DC device to be able to charge the cranking battery, the DC/DC device should draw no more than 50 amps, for a 40 amp DC/DC device.

Older type DC/DC device can draw high currents but it is unlikely to be drawing 200 amps.

[Milton477]

You are right Drivesafe, I shouldn't have to disconnect but my D4 charging system has it's own mind. My alternator is standard whatever that may be. The modern DC2DC pushes 50 amps into my van's LifeP04 batteries while drawing around 60 amps from the D4.

[DiscoJeffster]

You are right Drivesafe, I shouldn't have to disconnect but my D4 charging system has it's own mind. My alternator is standard whatever that may be. The modern DC2DC pushes 50 amps into my van's LifeP04 batteries while drawing around 60 amps from the D4.

Standard D4 is 220amp alternator. Replacements though came out at 180amp for whatever reason. That’s what I fitted to mine when I replaced mine

[Milton477]

I guess that I should look after my original then.

[drivesafe]

You are right Drivesafe, I shouldn't have to disconnect but my D4 charging system has it's own mind. My alternator is standard whatever that may be. The modern DC2DC pushes 50 amps into my van's LifeP04 batteries while drawing around 60 amps from the D4.
I was working on a 40 amp DC/DC device and your 50 amp unit would draw up to 60 amps.

Something is not quite right, unless you were it traffic, driving slowly which would mean your revs were low, otherwise, at any normal speed, your alternator output current can be up to it’s maximum, regardless of the output voltage.

[Ferret]

Something is not quite right, unless you were it traffic, driving slowly which would mean your revs were low...

It's in 'Park'

[Ferret]

Hi Ferret, that is nothing more than a line on a page, it gives no actual voltage reading, just a line on a page.

Well you should have the raw data by now. Scale the chart any way you like.

[drivesafe]

Well you should have the raw data by now. Scale the chart any way you like.
Thanks Ferret, will do.

[drivesafe]

You are right Drivesafe, I shouldn't have to disconnect but my D4 charging system has it's own mind. My alternator is standard whatever that may be. The modern DC2DC pushes 50 amps into my van's LifeP04 batteries while drawing around 60 amps from the D4.
Hi again Milton, you may have a load exceeding your alternator’s capacity, and what you are doing is probably your only option.

Can you post up full specs for you setup, like what isolator you have in the D4, and also what other accessories you have, such as driving lights, how many and what type.

Also, do you have any idea of your driving habits while towing?

[INter674]

Ferret, I’m with you. Post the CSV of the data. I’ve seen similar. Stupid car love to deplete the battery. It probably explains why these vehicles only get 3 odd years from a battery yet others get twice that on average. My Audi got 11 years out of its! It also explains why people endlessly tell you to put it on a charger monthly if you want the battery to survive. No other car I’ve owned needed this level of attention for its battery.



I'm pretty sure batteries are not built to last as long anymore.

Several Optima batteries across 3 trucks we've had in the past lasted longer in the same vehicle in the past. Indeed the last lot of blue tops were very dissapointing to the extent we complained about 5 of them only to be told @3 years was an acceptable lifespan. We don't buy them anymore.

Likewise we run a lot of machinery and previously had very good runs out of basic Exide/Century/Marshall N70 type batteries...but not so in recent years. I spoke with a major Aus battety supplier for 30 years who admitted that modern lead acid units he supplied did not last like the old ones....whatever that means. More or less get used to it I guess😐

Yes I do understand that modern vehicles draw more current etc etc....but why don't they last like my old man's batteries that gave 10 years even over the depth of UK winters?

[Tombie]

I went away from Optima after having 4 fail completely.
Seems they make them in Mexico now and the QA/QC is much lower.

Switched to Bosch & SSB and haven’t looked back.

[DiscoMick]

Interesting discussion on this topic here:

D4 battery charging issues (https://r.tapatalk.com/shareLink/topic?url=https%3A%2F%2Fwww%2E4x4community%2Eco%2E za%2Fforum%2Fshowthread%2Ephp%3Ft%3D198346&share_tid=198346&share_fid=15442&share_type=t&link_source=app)

[drivesafe]

Interesting discussion on this topic here:

D4 battery charging issues (https://r.tapatalk.com/shareLink/topic?url=https%3A%2F%2Fwww%2E4x4community%2Eco%2E za%2Fforum%2Fshowthread%2Ephp%3Ft%3D198346&share_tid=198346&share_fid=15442&share_type=t&link_source=app)
Amazing, same old same old.

It amuses me how often the claim that a DC/DC will charge your batteries to 100%.

Yet not once have I ever seen any statement made indicating just how long it takes to charge a low battery to 100%