General RV Solar Questions?

rctour wrote:
I really like my solar panels but one thing I have underestimates is what to do with all of that energy.

We do remote camping and have found that the sun is pretty simple to capture, but you need something to hold on to it. A single 12 battery is totally insufficient, we have three house batteries and three more would be better, in-fact you can't have enough battery power.

That is an overly broad statement that for many is completely false. We use at most 22 AH during the night with our RV and a single 110 AH battery could go for two days and still be well above the 50% DOD.

Anyone planning to boondock should first invest in a Trimetric or similar digital charge metering device so they know exactly how much charge is being consumed and how quickly it is restored when driving or plugged into shore power. Otherwise you do not have a clue.

With our two 110 AH batteries we could go for 4-5 days and then on the 6th day stay at a campground with 110AC and recharge the two batteries by the following morning. Part of the recharging would be initiated by the engine's alternator and then the charging completed with the 110AC power source.

You want to be able to go through the night and have 50% of your battery bank's capacity remaining. The amount of battery capacity you need depends on your RV's fridge, furnace and use, TV usage, tungsten or LED lights, and other factors that vary by RV, type of use, and time of the year. Whatever the amp hours of current that are used and need to be replace you can do the math based on the amps of output from a solar panel with most producing around 6 amps per hour of sunlight.

The Kyocera 140 Watt panels are very popular in large part due to their form factor, they are long and narrow, and they easily fit on the roof without potential problems with shading from something else on the roof or having them obstruct a skylight or vent.

Panels need to be matched only with regard to voltage output. Most RV panels are 17.7 Voc output, like the Kyocera (and the panels from AMsolar.com and others), but some put out 34 volts. The higher voltage output is better as there is less current loss with distance with any given gauge of cable run from the panels to the charge controller. Lighter gauge wiring is easier to run and more likely to attach to the charge controller without the need for jumper wires.

Check the charge controllers specs as it will state the maximum amperage it can handle at a given input voltage. So long as you stay within its limits it should be OK.

As with others I overbuilt my solar system and it produces 3x what we actually need. Even with the wiring gauge many will advise wires that are 4x as thick as needed as the difference with the short runs in an RV mean the difference between 1% current loss and maybe 4-5% loss.
In the real world that means that instead of recharging the battery bank in 5 hours it might take instead as long as 5 hours and 13 minutes.