I’m assembling my bill of materials for my 200 watt camper install. I’ve decided to use an MPPT controller and install two 100 watt flexible panels in series, but I have three questions.
1. It is never explicitly stated, but I assume when you say gel batteries that you also mean AGM batteries. Is that correct? 2. I am trying to figure out how to minimize messy cables on my roof, so I was wondering about the reason for different lengths on the pos 5.9” versus neg 17.7” solar panel cables. I know I can get different length cables with MC4 connectors, but do you have any other recommendations for minimizing cable runs? 3. I have a Renogy 100 watt solar suitcase with its own controller. I don’t think it makes sense to tie the suitcase into the permanently installed system, but will it be a problem to connect the solar suitcase directly to the battery (bypassing the installed controller) and charge batteries from both sources?
1. No, AGM are considered SEALED and Gel are gel! (controllers generally have GEL SEALED and FLOODED option, some may have Li and USER for programming)
2. Common to buy one Mc4 cable and cut it in 1/2 or whatever is needed for the + and neg. So ya connect one panel to the other and have one wire from each to run to the controller. The cut ends go to the controller.
3. no issue, connect as many chargers as you like at the same time (don't disconnect the suitcase controller), just hook the clips to the battery.
Is it true that with an MPPT controller I can put two 100 watt solar panels together in series that optimally operate at 18.9 volts for a combine output of 37.8 volts and the MPPT controller will take that voltage, step it down and charge my 12V AGM battery system at the normal 14.5 volts (or whatever is optimal at that time)?
In other words, an MPPT controller with two 100 watt solar panels in series will properly charge my RVs 12 volt system.
Last Edit: Oct 11, 2018 14:17:51 GMT by trailpixie
Yes, that is exactly what MPPT does. 2 in series is optimal for 12v charging. The MPPT controller has a built in 'transformer' that takes the input power and transforms it to charge a battery. This assumes your MPPT can handle the input voltage being doubled, I'm sure it can, most can handle 100v or more.
You would not series your panels if you had a PWM controller!
Somewhere in the specs or in the menu for the charge controller youll see all the predefined specifications for the GEL setting. You will need to compare that to optimas charging specs. The gel option is usually close enough to get by, going to the user option and setting it up exactly as defined by the battery manufacture usually results in a little better performance.