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C00P
17th May 2015, 10:24 PM
I have a caravan with two 80W panels on the roof charging the main van battery through a charge controller.
I also have a pair of portable fold-out panels, 100W total, with their own inbuilt controller.
It would be useful to connect these extra panels into the existing system.
Should I (a) by pass the controllers on the panels and simply feed their output directly to the charge controller in parallel with the existing panels, or (b) feed the portable panels into one of the DC battery outlets using their own controller, or (c) something else?

Or do you need more information to answer this?

Coop

bee utey
18th May 2015, 06:52 AM
Just plug the portable set into a power connection near the battery and they'll be fine. The only thing to note is that your cables should be thick enough to avoid too much voltage loss between the controller and the battery.

C00P
18th May 2015, 10:57 PM
Thanks Bee utey. I thought that would be the case, but I wondered if the two controllers would squabble. But I guess all they see is the battery voltage and lifting that with the input from another pair of panels isn't going to change the way the controllers operate.
Cheers

Coop

kelvo
19th May 2015, 12:12 PM
Thanks Bee utey. I thought that would be the case, but I wondered if the two controllers would squabble. But I guess all they see is the battery voltage and lifting that with the input from another pair of panels isn't going to change the way the controllers operate.
Cheers

Coop

AFAIK you are correct Coop, the two regulators will confuse each other. You will only effectively be using the power from one controller.

Better to bypass the regulator on your portable panels and connect this into your existing charge controller. Make sure it can accept the total input watts from all your panels first.

bee utey
19th May 2015, 12:32 PM
AFAIK you are correct Coop, the two regulators will confuse each other. You will only effectively be using the power from one controller.

Better to bypass the regulator on your portable panels and connect this into your existing charge controller. Make sure it can accept the total input watts from all your panels first.
Not sure how regulators can get "confused" unless they're smarter than the average kelpie. My bush camping system has two separate regulators and never had any problems. If my batteries are sufficiently low at dawn both regulators together can't lift the battery voltage above 14V until the batteries recharge and one regulator then slows its charge rate first.

kelvo
19th May 2015, 09:27 PM
Not sure how regulators can get "confused" unless they're smarter than the average kelpie. My bush camping system has two separate regulators and never had any problems. If my batteries are sufficiently low at dawn both regulators together can't lift the battery voltage above 14V until the batteries recharge and one regulator then slows its charge rate first.

My understanding is this;
Regulator A with 120w panel is changing the battery at 14.2V, regulator B with 120w sees this 14.2V and thinks the battery is charged so it goes into 'float' mode. So in effect you are only using 120w to recharge the battery.

Using one regulator with both 120w panels connected would give you the full 240w of power to recharge the battery.

The above is assuming your solar regulator is able to accept a 240w solar input and is also able to output the 240w.

A 10amp regulator may be able to have 240w of solar connected but can only ever output 10amps. So if using one regulator you would need to make sure it is the correct capacity to make the most of your setup.

bee utey
19th May 2015, 09:55 PM
My understanding is this;
Regulator A with 120w panel is changing the battery at 14.2V, regulator B with 120w sees this 14.2V and thinks the battery is charged so it goes into 'float' mode. So in effect you are only using 120w to recharge the battery.

Using one regulator with both 120w panels connected would give you the full 240w of power to recharge the battery.

The above is assuming your solar regulator is able to accept a 240w solar input and is also able to output the 240w.

A 10amp regulator may be able to have 240w of solar connected but can only ever output 10amps. So if using one regulator you would need to make sure it is the correct capacity to make the most of your setup.
If indeed one set of panels plus one regulator can raise the battery voltage to 14.2V then no matter which way you add the extra panels the voltage will attempt to rise above the regulator's set voltage and be cut off from supplying the batteries. A battery cannot accept a high current and stay below 14.2V if it is nearly full. That is simply how a lead acid battery works. It is not some kind of bucket you can fill at a maximum flow rate of amps right to the top.

The point is that if the batteries are sufficiently discharged or there is a big enough load on the system (eg an appliance drawing 500W via an inverter) then both sets of panels with their respective regulators will see a voltage well below 14V and they will both supply full current to the system.

Oh and if you hook up more panels to a regulator than it is designed to handle then you will probably burn it out. They have specifications it's wise not to exceed.

kelvo
19th May 2015, 10:26 PM
If indeed one set of panels plus one regulator can raise the battery voltage to 14.2V then no matter which way you add the extra panels the voltage will attempt to rise above the regulator's set voltage and be cut off from supplying the batteries. A battery cannot accept a high current and stay below 14.2V if it is nearly full. That is simply how a lead acid battery works. It is not some kind of bucket you can fill at a maximum flow rate of amps right to the top.

The point is that if the batteries are sufficiently discharged or there is a big enough load on the system (eg an appliance drawing 500W via an inverter) then both sets of panels with their respective regulators will see a voltage well below 14V and they will both supply full current to the system.

Oh and if you hook up more panels to a regulator than it is designed to handle then you will probably burn it out. They have specifications it's wise not to exceed.

I said "Regulator A I with 120w panel is charging the battery at 14.2v" not meaning the battery is actually at 14.2v ie remove all charging input and the battery voltage could drop to 12v. The second regulator sees the 'charging' voltage from the first regulator and thinks this 14.2v is the battery voltage, at which point the second regulator goes into float mode. NOTE all voltages being used are random voltages, actual voltages may differ ;)

Your last comment was covered when I said "So if using one regulator you would need to make sure it is the correct capacity to make the most of your setup."

bee utey
19th May 2015, 10:37 PM
I said "Regulator A I with 120w panel is charging the battery at 14.2v" not meaning the battery is actually at 14.2v ie remove all charging input and the battery voltage could drop to 12v. The second regulator sees the 'charging' voltage from the first regulator and thinks this 14.2v is the battery voltage, at which point the second regulator goes into float mode. NOTE all voltages being used are random voltages, actual voltages may differ ;)


Yes and adding two more panels to the first regulator will not charge a battery any faster as it's already at a high output voltage in your example. The regulator will simply reduce the current to match.

Oh and that bit about the voltages being randomly chosen shows you don't understand electrics, with battery charging achieving the correct voltage is very important.

Pedro_The_Swift
20th May 2015, 07:14 AM
sell the foldouts, buy another rigid panel, bolt to the roof, connect to current(geddit!) controller.;)

C00P
23rd May 2015, 08:25 PM
Well, that's been a most interesting discussion folks!
I didn't mean to start a jousting session. I guess the proof of the pudding is in the charging....
And maybe Pedro's suggestion is a better approach, but will try the direct connection to the battery first and monitor the current coming from each panel, just for interest. Thanks for your advice.
Cheers

Coop

d2dave
23rd May 2015, 08:50 PM
The problem with pedro's suggestion means you have to always park your van in the sun.

I plan to put panels on the roof of my van, but I will still carry my portables.

Also you can orientate the portables to correct angle and to follow the sun, whereas on a van roof they will never produce maximum currant as they are lying flat.

Pedro_The_Swift
24th May 2015, 09:09 AM
yep,, park in the sun.:cool:
shade is bad for caravans,,
and tents, and people too really.

shade means trees.
trees drop limbs.
limbs hurt anything below them.

if your storage setup is on that much of a knife-edge that you have to spend all day chasing the sun,,
you need to re-think your leisure time priorities. ;)

d2dave
24th May 2015, 09:40 AM
Its alright for you Queenslanders where it does not get hot.

Try parking a caravan in the sun when it is often above 40 degrees.

C00P
22nd August 2015, 11:14 PM
For those who followed this thread to the bitter end, I had a chat with some folks at the Mt Barker 12-volt shop today, where I originally purchased my portable panels. They confirmed that simply hooking the portable panels (with their own built-in regulator) across the batteries would assist with charging the batteries and that there was no need to connect the portable panels via the existing charge controller on the van. They said both sets of panels would react to the battery voltage and adjust their charging accordingly as the batteries neared full charge.
Cheers

Coop

p38arover
6th December 2017, 04:50 PM
Just plug the portable set into a power connection near the battery and they'll be fine. The only thing to note is that your cables should be thick enough to avoid too much voltage loss between the controller and the battery.

I was thinking of buying additional folding panel (2 x 80w folding) as my existing 120w panels don't provide enough power in winter where I camp in a deep valley. The sun doesn't clear the eastern ridge until fairly late and drops behind the western ridge fairly early. I wasn't sure if there would be an issue with just paralleling the existing 120w and new 160w units.

Note that the 120 watt rating can be taken with a grain of salt. I never get above 7.5 amps out of the panel even in summer.

bee utey
6th December 2017, 06:31 PM
I was thinking of buying additional folding panel (2 x 80w folding) as my existing 120w panels don't provide enough power in winter where I camp in a deep valley. The sun doesn't clear the eastern ridge until fairly late and drops behind the western ridge fairly early. I wasn't sure if there would be an issue with just paralleling the existing 120w and new 160w units.

Note that the 120 watt rating can be taken with a grain of salt. I never get above 7.5 amps out of the panel even in summer.

The watt rating of a solar panel is at a panel surface temperature of 20°C and at around 17 to 18 volts. Panel output current doesn't increase enough to compensate for the voltage drop under load, and of course no panel will stay at 20°C out in the full sun for any amount of time. The only regulators that can make use of a larger amount of the panel's rated power output are 'maximum power point tracking" (MPPT) types and cost a fair bit more than the standard type.