Use of home solar panel for RV

Your Vmp~32 volt and Imp-9.26 amp single panel will work with almost any MPPT (maximum power point tracking) solar charge controller....

MPPT controllers can efficiently "down convert" higher voltage/lower current from a solar array to a lower voltage/higher charging current for a battery bank.

There are specific PV Input vs Charge Controller Battery output conditions... Your panel should work with just about any MPPT controller...

Minimum suggested charge controller:

• 300 Watt panel * 0.77 panel+controller derating * 1/14.5 volt charging = 15.9 ~ 16 Amp suggested minimum MPPT solar charge controller
• 300 Watt panel * 1/0.66 panel+controller "optimum" max rating (various reasons) * 1/14.5 volts = 31 Amp suggested "largest" MPPT controller

16-31 amp MPPT charge controller (with 12 volt battery capability) is a good range... Below 16 amps, the MPPT controller will "throttle" output current to max rated current (safely). Over ~31 amp rating--Just bigger than you need (more costly)--But will work fine too.

There are non-MPPT controllers--They will work but can cost you upwards of 50% of your 300 Watt panel (i.e., ~150 Watt output from panel). Non-MPPT controllers are "cheaper", but will be much less than optimum for your panel.

You can go with a larger MPPT controller if, for example, you plan on adding a 2nd 300 watt panel later (if you have roof space).

For a 200 AH 12 volt battery bank--A good fit would be 10% to 20% of battery bank AH capacity (i.e,. 20-40 amps) charging current. Depending on battery specs... You could pump upwards of 50% or even higher--Depending on you battery bank & BMS ratings/specs.

Of course, this also depends on your expectations (how may Watt*Hours or Amp*Hours@12 volts do you expect to use per day, when and where camping (snow camping in winter, vs sunny south west non-winter camping).

Lithium Ion batteries have much better charging characteristics vs Lead Acid--LiFePO4 batteries are near 100% efficient (charging/discharging) and can be recharged at "full current" to near 100% capacity. Lead Acid batteries slow down charging as they near 80%+ state of charge (2-6 hours of "absorb" charging)...

-Bill

This is a bit difficult to generalize a useful answer for... Location, possible tilt of solar panels (flat to roof, tilted to latitude, facing south), panels must be in full sun--Any shading (trees, etc.) will generally "kill" the output of a shaded solar panel/array by at least 50% or more.

Just to give you an idea of the solar variability... Centennial Colorado, 1kWatt array tilted to 40 degrees from horizontal, facing south:
https://pvwatts.nrel.gov/pvwatts.php



That is pretty good sun overall... Anything 3 hours of sun per day or better is "reasonable" for solar electric.

The next thing to look at is your loads... For example if you run an RV propane heater with fan they are around 9 amps @ 12 volts typically--Run that "over night" for 10 hours, and you are looking at 90 AH or almost 1/2 of your battery bank capacity (200 AH).

A more powerful laptop computer can use 30 Watts (or more)... Run that for 8 hours (editing videos, watching movies, etc.):

• 30 Watts * 8 hours = 240 WH
• 240 WH * 1/0.85 AC inverter eff * 1/12 volts = 23.5 AH @ 12 volts (1/4 of your bank capacity in a day).

600 Watts of solar panel * 5.88 Hours of sun (1 yr average) * 0.52 off grid system eff = 1,835 WH per day of solar

Assume you don't want to use the genset and only use 50-65% of predicted power:

• 1,835 WH * 0.65 solar fudge factor = 1,193 WH per "average day" with fudge factor
• 1,193 WH per average day / 12 volts = 99 AH @ 12 volts of "average solar day" + fudge factor of AH generated  

You can see that running heat during winter, with poor sun, solar panels flat to roof--Even just running the heater over night can quickly drain a 600 Watt system.

There are lots of ways of slicing the dicing the data... Just a couple examples that can give you a rough idea of how to make your own mathematical models.

There are always other issues too... In sub freezing weather, lead acid batteries work well, but temporarly lose AH capacity when very cold.

Li Ion batteries generally cannot be electrically cycled much below 50F (need to keep Li Ion batteries "warm").

Your thoughts, questions, etc.?

-Bill