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Author: Subject: Multiple charge controllers from one panel to charge different batteries?
Doug/Vamonos
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[*] posted on 11-2-2016 at 08:07 AM
Multiple charge controllers from one panel to charge different batteries?


Hi. Can I connect more than one charge controller to a panel in order to charge different types and sizes of batteries? What I want to do is set up a 100 watt panel to pos and neg buss bars and then connect four small charge controllers in order to charge my car battery, quad battery, and two optima boat batteries while I am away. I don't want to charge the batteries in parallel since I don't want them equalizing together. The simple alternative is to buy four separate solar/battery maintainers, but I have the panel and the charge controllers to try this instead. Thanks.

[Edited on 11-2-2016 by Doug/Vamonos]

[Edited on 11-2-2016 by Doug/Vamonos]

[Edited on 11-2-2016 by Doug/Vamonos]
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mjs
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[*] posted on 11-2-2016 at 10:13 AM


If the controllers are all PWM then give it a try as those controllers regulate output based on the battery voltage. A MPPT controller tries to adjust the load that the panel sees to maximize panel output and then to feed the battery the needed charge parameter. Multiple MPPT controllers on the same panel will probably end up fighting each other and not work very well.


[Edited on 11-2-2016 by mjs]
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[*] posted on 11-2-2016 at 10:28 AM


I agree with above, using PWM controllers should work fine in parallel. They are essentially just smart switches.



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[*] posted on 11-2-2016 at 11:19 AM


why would a mppt controller fight with the others?

the current coming down is what it is...

the controller stops extra current at the controller for the bank you are charging

if you splice the current BEFORE a controller then each controller get "un-cut" current from the panels

the controller shouldn't know what the other controllers are doing

another question is why charge all the batteries in the quad boat and car...just disconnect those ....no connection no loss...batteries in a store last a long time




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[*] posted on 11-2-2016 at 12:21 PM


Quote: Originally posted by Bob and Susan  
why would a mppt controller fight with the others?

the current coming down is what it is...

the controller stops extra current at the controller for the bank you are charging

if you splice the current BEFORE a controller then each controller get "un-cut" current from the panels

the controller shouldn't know what the other controllers are doing

another question is why charge all the batteries in the quad boat and car...just disconnect those ....no connection no loss...batteries in a store last a long time


The current and voltage of a panel can and do vary. If you look at the specs on a solar panel they will usually list STC and NOTC outputs that are different. Also the maximum voltage (Voc) and current (Isc) as well as the optimal operating current (Imp) and voltage (Vmp). The MPPT controller varies the load the panel using Ohm's law to obtain the maximum wattage (Imp x Vmp) output of the panel under different conditions and the needed charging requirements.

With multiple MPPT controllers they are working against each other as one adjusts the other tries to respond by making its own adjustments which the first unit sees and then tries to adjust for and then the second adjusts and then the first, etc, etc.

The PWM controller only looks at the battery voltage and adjusts the charge parameters based on that. It does not adjust the load the panel sees to try and maximize the panel output.

[Edited on 11-2-2016 by mjs]
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[*] posted on 11-2-2016 at 03:56 PM


why wouldn't this work

panels.jpg - 55kB




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Doug/Vamonos
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[*] posted on 11-2-2016 at 04:23 PM


Good! The worst I can do is burn down the camp. :-)
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[*] posted on 11-2-2016 at 04:29 PM


to be safe you might want to add diode's between panels and controllers
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[*] posted on 11-2-2016 at 05:12 PM


why a diode???
and what kind???

...for sure a breaker




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[*] posted on 11-2-2016 at 05:33 PM


Quote: Originally posted by Bob and Susan  
why a diode???
and what kind???

...for sure a breaker


well lets assume the controllers don't have diode protection, what you have is two batteries in parallel...correct? what happens when one bank is charged and the other isn't? undercharging, shorted batteries, even if the controllers have built in diodes it can't hurt, right?:light:


on edit....of course I could be wrong!

[Edited on 11-3-2016 by willardguy]

[Edited on 11-3-2016 by willardguy]
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[*] posted on 11-2-2016 at 05:42 PM


Cheap as can be and you can just plug it into your inverter.

[Edited on 11-3-2016 by soulpatch]
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[*] posted on 11-2-2016 at 05:46 PM


Quote: Originally posted by soulpatch  
Cheap as hell and you can just plug it into your inverter.


1 1/4 amp per side.....hope you have alot of time! :?:
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[*] posted on 11-2-2016 at 05:48 PM


Quote: Originally posted by willardguy  
Quote: Originally posted by soulpatch  
Cheap as hell and you can just plug it into your inverter.


1 1/4 amp per side.....hope you have alot of time! :?:


I edited for the 4 bank charger.
Well, he said it was for when he was gone. I imagine it is for a least a few days.
I've been wrong before.

How many amps you think he's going to get out of a 100W module in full sun that is probably mounted flat on a roof in a dusty environment?
Not many, if I understand temperature derating, soiling and age degradation in any way whatsoever.


[Edited on 11-3-2016 by soulpatch]
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[*] posted on 11-2-2016 at 05:59 PM


yeah nix the inverter idea...but I think what he's after makes sense! four small cheap charge controllers, just keep em isolated!
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[*] posted on 11-2-2016 at 06:07 PM


Quote: Originally posted by willardguy  
yeah nix the inverter idea...but I think what he's after makes sense! four small cheap charge controllers, just keep em isolated!


Why nix the inverter idea?
All he'd have to do is leave it on, plug in the charger and he's good to go.
He isn't going to get a whole lot of amperage out of 1 module.
Doesn't have to assemble a busbar, circuit protection, anything.
Plug it in and don't worry about it.
Once they are in float mode it shuts off and the inverter idles.
Me? I wouldn't worry about any of that.... unless you are gone 6 months at a time you are not going to lose much of a charge unless you use really crappy batteries.
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[*] posted on 11-2-2016 at 06:26 PM


Quote: Originally posted by soulpatch  
Quote: Originally posted by willardguy  
yeah nix the inverter idea...but I think what he's after makes sense! four small cheap charge controllers, just keep em isolated!


Why nix the inverter idea?
All he'd have to do is leave it on, plug in the charger and he's good to go.
He isn't going to get a whole lot of amperage out of 1 module.
Doesn't have to assemble a busbar, circuit protection, anything.
Plug it in and don't worry about it.
Once they are in float mode it shuts off and the inverter idles.
Me? I wouldn't worry about any of that.... unless you are gone 6 months at a time you are not going to lose much of a charge unless you use really crappy batteries.



well okay by me, I just don't see firing up an inverter to run (4) 1 1/4 amp charging circuits for $190 when you could buy (4) 4 or 5 amp charge controllers for $30 apiece......but thats just me :D
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[*] posted on 11-2-2016 at 06:31 PM


True, but the other costs of doing it safely.
I see your point!

Seems to me if you put a full charge into them all before you leave if you not gone for more than a few months there is nothing to worry about, though.
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[*] posted on 11-2-2016 at 06:50 PM


Hey Frank. Yes, I like that idea and would have done it (it was my first choice) but I have this fear of leaving my inverter on while I'm gone for months at a time? Do I worry too much? For an update, my system is (8) 100 watt panels wired in two series at 48 volts, going to an Outback FM80Flex controller to a bank of six large 105 amp 12 volt gel batteries wired at 12 volts. The inverter is Xantrex Prowatt 2000.
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[*] posted on 11-2-2016 at 07:24 PM


I used to have these little, inexpensive charge controllers that I hooked to my trailer batteries at one point.
Those would be perfect but I am having a hard time locating them right now... been awhile!


Ja! Found them... been so long I'd forgotten..... I was trying to find what I used to keep my trailer battery charged while I was gone....

This would be EZPZ and fit your design criteria perfectly:

Morningstar Corporation SunGuard SG-4 Charge Controller

Cheap on Wholesale solar but I am sure other people have them at very affordable rates, too.

You could scab off of one module to a bus and make this work.
I am not sure where your combiner box is but I am sure it is pretty straightforward.

[Edited on 11-3-2016 by soulpatch]
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