Series, parallel, or series parallel

[passengeroftime]

I really appreciate your responses. Sincerely. You gave the answers I needed.

[sdold]

I think if it was me I'd wire them all in series and use an MPPT controller, something like a Victron Smartsolar 150/35, which would limit the current to the battery to 35A which is close to the typically-recommended max of C/8 (37.5A for a 300AH battery). Panels I work with typically run no more than 80% of nameplate power anyway, and they're angled toward the sun, so if they were laying horizontal on a van I would think it would be even less. I'd try it and if I felt like I had too much panel for the application, I'd just remove one of them.

[SunEagle]

Thanks for the fast response SunEagle. I don't actually have any batteries installed or even have a controller yet. I have to 2 panels installed and was about to install the other set. Van build out is in progress. If I was to wire all 4 panels in series, would 10g be ok? Would this be worth it as far as performance is concerned because of the mismatched panels? I only planned on having one 300AH battery in the 12V system. I have alot of room on top of the van and figured more panels, more power.

I don't think the panel mismatch along the Vmp is a problem but the system will be reduced to the lowest Imp panel.. So you can wire them all in series but again if you have an MPPT CC you will get 33% more charging amps then with a PWM type. Also if those panels are mounted flat you will reduce their output. The amount will depend on the position of the sun and van. So maybe that 300Ah battery may be ok if you don't exceed a C/8 charge rate which calculates out to 300ah / 8 = 37.5 amps. Too many charging amps could cook the battery system. Also while you will have a nice amount of panel wattage the system is really based on the battery system. A 300ah FLA type battery should safely provide about 900 watt hours (300ah x 12v x 25% = 900wh) where you really don't diescharge the batteries more then 25%

[passengeroftime]

Thanks for the fast response SunEagle. I don't actually have any batteries installed or even have a controller yet. I have to 2 panels installed and was about to install the other set. Van build out is in progress. If I was to wire all 4 panels in series, would 10g be ok? Would this be worth it as far as performance is concerned because of the mismatched panels? I only planned on having one 300AH battery in the 12V system. I have alot of room on top of the van and figured more panels, more power.

[SunEagle]

Hello passengeroftime and welcome to Solar Panel Talk

I would think that wiring the same panels in series and then the second pair in parallel to the first set.

That should get you about 670 watts which if they are used to charge a 12v battery will require a 60amp MPPT charge controller. That unfortunately will require 60 amp wire and fusing between your combiner box and the charger and then again between the charger and battery system.

Your battery system will also need to be about 550ah system since you could generate 55amps of charging. (670w / 12v = 55.8amps. Since you only have 2 sets of panels you really don't need fusing for each set. But if you wire the panels so there are more then 2 sets (say all 4 in parallel) you would need a fuse for each panel in the combiner box.

I do not see a solution where you can safely use that 10g wire unless you use only one panel.

So my question is what is your battery system voltage and amp hour rating? Based on that value may determine the number of panels you use.

[passengeroftime]

Hi, I'm new to this forum and wanted to ask a question. I have 4 solar panels. 2 and 2 are exactly the same. I'm trying to figure out my best option to wire these panels on top of my van. I'd like to use only 10g wire and get the most power out of all panels. The panels are pretty similar but different and that's what was making me think of wiring in series parallel. Wiring in series sounds like a might not get the best performance when one panel doesn't have good lighting but I'm not sure.

Panel details:

Renogy 175 Watt 12V (quantity of 2)
Max Power: 175W Open Circuit Voltage: 21.6V
Short Circuit Current: 10.35A
Opitmum Operating Voltage: 17.95V
Optimum Operating Current: 9.75A

AM Solar SF160 (quantity of 2)
Open Circuit Voltage (Voc): 22V
Short Circuit Current (Isc): 9.5A
Maximum Power: 160W
Maximum Power Voltage (Vmpp): 18V
Maximum Power Current (Impp): 8.88A


What is my best option for wiring? How many amps would I have?

Shane