Originally Posted by thompooley
Be sure not to add too much voltage when adding PV modules to your RV. You can purchase a few 50 watt panels on eBay for about $2-3 per watt and install them in parallel, not serial, to maintain a voltage of 14 to 18 volts DC. It is better to use all the same wattage panels. I swapped out my two wet cell deep cycle batteries for 4 12v
deep cycle wheel chair batteries which charge more quickly and last longer when using them to power fans and LED lighting. You don't need marine cranking amps to power your RV's interior.
Just to add a few comments to the above:
There are many 100 watt panels available that will fit on an Airstream (20-21" wide). There is no need to use 50 watt panels, which by themselves are almost insignificant in their amperage output (2-2.5 amps Voc at most).
Matching the wattage of the panels doesn't matter as much as the output voltage
....especially if you are using an MPPT controller. You can easily mix/match panel sizes for maximum coverage of your roof as long as you follow the voltage matching rule. And speaking of voltage, you want panels with a minimum
of 17.5 volt output so that they provide sufficient 'headroom' to allow the solar controller to charge the batteries at a bulk/absorb voltage of 14.2-14.8VDC, depending on your battery type.
And speaking of batteries, true deep cycle, whether liquid lead acid or AGM, have proven themselves to be the best for RV applications. Avoid dual purpose deep cycle marine batteries, which also double as starting batteries.
PM me if you have an specific questions.