Wiring Solar Panels in Series or Parallel

AnOldUR

Confused.

I have two 50W flexible panels that each produce about 20V. The solar controller I'm using says to not exceed 25V. This means that if I wire the two 50W panels in series I'd exceed that voltage.

The part that messed with my head was the the controller also said it, "Support(s) 100W Solar Panel Charging". Trouble is if wired in series the wattage is still at 100 but the voltage goes up and the amperage goes down.

Can a controller handle a higher voltage if the amperage is lower or is the voltage the only determining factor for overloading a controllers?

Grumpy_G

No. The controller has two limits, voltage and current and you don't want to exceed either. The technical data for the solar controller should list both. 

Parallel it is  

bergger

I agree with @Grumpy_G .  Series will not work with your controller.  Parallel will allow you to output 100w, both panels added together, but keep the voltage at 20v, the voltage of one panel.  Parallel seems to be the way to go with your controller.  That's how my two portable 100w panels are wired to my controller. 

AnOldUR

Thanks! I had originally planned to go with parallel, but had read that series would result in lower amperage and require lighter (cheaper) gauge wire between the panels and the controller. Its not worth if it will damage the controller.

Grumpy_G

@AnOldUR that's correct, and in fact larger solar installations e.g. at a home do run higher voltages so they don't need finger thick copper wiring. But you do need a solar charger/controller that can work with the higher voltage and those often do also need 24V or 48V battery systems.

KK1L

100W at 20V is 5A. Even if using 20' of 20ga wire (pretty small) you would only lose 0.5W in the wire or 99.5% efficient

AnOldUR

The two panels are wired in parallel and mounted on the freedom panels of our Wrangler. We'll be doing a two night uCamp dry run later in the week. For now I have a 12V cooler running in the back of the Jeep. I'll give it a few days sitting in the driveway before hitting the road. It will be interesting to see if the 100W's can maintain the charge in our spare 100Ah LiFePO4 battery that rides in the back of the Jeep.