Roof solar panels, go 2 50w or 100w

[dwh]

panel voltage needs to be at least **5V** above the battery voltage

Yea, +5v, dunno where that dot came from, but I didn't catch it.

 

[dwh]

Sorry for the neebe question what is 100/30 or 75/15 ?

Victron naming convention. Refers to the max volts/amps the unit can handle - 75v/15a, 100v/30a.

 

[john61ct]

Volts is input Voc max, keep 10% below, can fry the unit.

Amps spec is max charging **output**, lots of tolerance on the input side to allow for overpanelling.

 

[94Discovery]

Thanks ��

 

[rayra]

Yeah seriously. Please educate me why having multiple connections would be better, if that be the case use 5 20 watt panels? Wiring diagram and diodes ********** of making a simple task not so simple?

Redundancy, for starters and primary concern. Have two panels and suffer a functional loss for whatever reason and you only lose half you capacity, instead of all of it. You want to be simple, go be simple. But don't think there's anything virtuous about creating a single point a failure in a vehicle designed to operate far away from the grid. Not when it is quite easy to build in options and redundancy before traveling.

 

[rruff]

Fewer higher-power panels is better than many.But make sure they're 24V nominal, ideally 40+Voc, can go up to 65.ideal is one per controller unless hinging two together for portability, then keep from any shade and wire 2x 20+Voc in series

Why higher voltage?

Makes sense if you are powering everything from an inverter, but what if you are 12v exclusively?

 

[dwh]

Why higher voltage?

Makes sense if you are powering everything from an inverter, but what if you are 12v exclusively?

Yea, in that quote he's talking about higher solar panel voltage, not higher battery voltage.

 

[john61ct]

MPPT requires panels to be at higher voltages than nominal 12V panels (usually 17-21Voc).

40V and up I believe for max extraction efficiency.

If you keep you panel voltages at nominal 12V don't bother getting MPPT, PWM is cheaper.

 

[rruff]

40V and up I believe for max extraction efficiency.

Ya, I didn't realize MPPTs were so efficient. Makes sense that you can increase amps by dialing in the volts for just what the batteries need.

I'd like to have a portable on a long extension and higher voltage makes sense there also.

 

[john61ct]

Yes, carrying fifty pounds of wiring around gets old pretty quickly.