Are these panels suitable for a 24V system?

[edk]

Greeting solar gurus -

I am in the process of buying a truck topper for camping. The vendor provides a complete 12V solution, but I am interested in 24V. (There is another forum for RVs but the title says 12V, so I came here.) I am limited to the panels they spec because of space and size constraints. Here are the published specs on the panels:

Maximum Power Output: 265W per panel (2 panels)
Panel dimensions: 880 x 1560 mm
Weight (Per Panel): 15 lbs
MFGR Represented Efficiency: 22.2%
Operating Voltage (Vmp): 31.92V
Operating Current (Imp): 8.31A
Open Circuit Voltage (Voc): 38.3V
Short circuit current (Isc): 8.98A

Questions:

1: using the Victron calculator I need to connect these in series for a 24V system. Does that look right to you? Or can I use them in parallel?

2: If connecting them in series, do I halve the possible charging current? Or does the magic of the MPPT controller give me the full power of the panels (minus losses)?

Related question: I would like to add AC power input capability for charging and appliance power, so when I am parked overnight I can plug into the facility's AC (aka shore power). I think I will need transfer switches or some such, but am having trouble tracking down how to do this. Any thoughts about where to find info on auto-switching of power? Space will be tight and I am trying to keep within a budget, so I am thinking I need to home-brew the solution, rather than buy a COTS system. Should I post in the RV forum?

Thanks!
Ed K

[SunEagle]

HI edk and welcome to Solar Panel talk. Any panel that has a Vmp greater than 30 volts will work just fine for a 24 volt system. As far as I am concerned both panels wired in parallel should work for you.

[jkirkebo]

Greeting solar gurus -

I am in the process of buying a truck topper for camping. The vendor provides a complete 12V solution, but I am interested in 24V. (There is another forum for RVs but the title says 12V, so I came here.) I am limited to the panels they spec because of space and size constraints. Here are the published specs on the panels:

Maximum Power Output: 265W per panel (2 panels)
Panel dimensions: 880 x 1560 mm
Weight (Per Panel): 15 lbs
MFGR Represented Efficiency: 22.2%
Operating Voltage (Vmp): 31.92V
Operating Current (Imp): 8.31A
Open Circuit Voltage (Voc): 38.3V
Short circuit current (Isc): 8.98A

Questions:

1: using the Victron calculator I need to connect these in series for a 24V system. Does that look right to you? Or can I use them in parallel?

2: If connecting them in series, do I halve the possible charging current? Or does the magic of the MPPT controller give me the full power of the panels (minus losses)?

You can wire both in parallell and series as long as the MPPT controller can take at least 100V input. A Victron SmartSolar 100/20 would be perfect in this case.

Series wiring will give you easier wiring and less voltage drop. The MPPT controller will convert the voltage and amps so you don't lose anything compared to parallell wiring.

[Liam]

Greeting solar gurus -

I am in the process of buying a truck topper for camping. The vendor provides a complete 12V solution, but I am interested in 24V. (There is another forum for RVs but the title says 12V, so I came here.) I am limited to the panels they spec because of space and size constraints. Here are the published specs on the panels:

Maximum Power Output: 265W per panel (2 panels)
Panel dimensions: 880 x 1560 mm
Weight (Per Panel): 15 lbs
MFGR Represented Efficiency: 22.2%
Operating Voltage (Vmp): 31.92V
Operating Current (Imp): 8.31A
Open Circuit Voltage (Voc): 38.3V
Short circuit current (Isc): 8.98A

Questions:

1: using the Victron calculator I need to connect these in series for a 24V system. Does that look right to you? Or can I use them in parallel?

2: If connecting them in series, do I halve the possible charging current? Or does the magic of the MPPT controller give me the full power of the panels (minus losses)?

Related question: I would like to add AC power input capability for charging and appliance power, so when I am parked overnight I can plug into the facility's AC (aka shore power). I think I will need transfer switches or some such, but am having trouble tracking down how to do this. Any thoughts about where to find info on auto-switching of power? Space will be tight and I am trying to keep within a budget, so I am thinking I need to home-brew the solution, rather than buy a COTS system. Should I post in the RV forum?

Thanks!
Ed K

Series works fine. The two panels together give you 76.6V Voc, just make sure your charge controller can handle it. Current doesn't get cut in half; the MPPT will take the 530W and turn it into roughly 18A going into your battery. For shore power switching, I'd recommend an all-in-one inverter/charger—much simpler. If you want to DIY, search for "automatic transfer switch + relay". There are tons of guides on RV forums.