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Discussion Starter #1 (Edited)
I set up a taylor dunn burden cart as a mobile solar generator with six 180 watt panels on top last year. regular 36v 6 x 6v lead acid batts.

Just built a trailer for it that has 4 x 180 watt panels, and can be connected via two sets of 5 panels. I've put each set of 5 in series ( over 105v) than run both parallel.

I can squeeze another panel on the trailer for a total of 5 on it, (11 panels total in system ) but it would throw the voltage out of whack.

Can I run the 6 panels on top of cart with one solar controller, and connect the 5 on the trailer to another controller, using the same battery bank on the cart?

https://www.youtube.com/watch?v=bp2RbBoT4OM
 

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Multiple charge controllers on the same battery bank are no problem at all. You are getting up into fairly high voltages in your strings, though, so make sure that the charge controller is rated to handle the full open circuit voltage.


If you are only charging to 36 volts, and you do not have long wire runs, a relatively high voltage coming off your panels is not really ideal. There is a sweet spot for efficiency, but I do not remember off the top of my head what it is as a percentage of battery voltage. Shorter strings might be better, but then you need to add combiner boxes, and you still get left with an odd panel out.
 

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Discussion Starter #3
Multiple charge controllers on the same battery bank are no problem at all. You are getting up into fairly high voltages in your strings, though, so make sure that the charge controller is rated to handle the full open circuit voltage.


If you are only charging to 36 volts, and you do not have long wire runs, a relatively high voltage coming off your panels is not really ideal. There is a sweet spot for efficiency, but I do not remember off the top of my head what it is as a percentage of battery voltage. Shorter strings might be better, but then you need to add combiner boxes, and you still get left with an odd panel out.
v

Its rated to 150v, and has worked fine for a year. actual voltageto controller is around 95v. Need to go larger on my transmission lines.
 

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To get 2 separate MPPT controllers to charge one battery, you need controllers with separate battery sensing cables. This way you can fool each controller into not seeing the input from the other controller.
The way MPPT controllers work is they stop charging every so often and read the battery voltage, they are looking for less than 12.8v on a12v battery so multiply it up from there to match the battery voltage you are using.
If the other controller is still charging, the first controller sees the charging voltage from the first controller, not the actual rested battery voltage, this will be higher than the 12.8v per 12v battery so that controller will determine the battery is fully charged and drop back to float voltage.
By using voltage sensing wires and a diode in the positive cable, the voltage is dropped by 0.7v and the charger will see a voltage lower than the target voltage and commence charging again.
The only other non voltage sensing MPPT controller that you can get to work properly in a multiple set up is the Victron units and you need to add all the other bits like the colour controller and BMV so the voltage sensing and end of charge as determined by the colour controller as the master and the others as slaves .... a rather expensive exercise.
What controllers are you using?


T1 Terry
T1 Lithium Mannum
Australia
 
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