Looking to add solar

On a PWM controller, what do the adjustable setpoints adjust?

On a small system with a PWM controller, what is adjusted based on battery temperature?

We use about 20ah per day when in conserve mode. That's a frig on gas, detectors on and LED lights. Spend most of time outside.

I have 2 GC2's @ 232a & I have bought a Renogy 200w ( 2 100w panels)that should produce about 11.5a total with 30a controller from Amazon. Awaiting delivery. Like you I only want a good recharge to limit gen use. I think it will do the job. I would suggest you upgrade your batteries to larger capacity true deep cycles.

Hi,

Group 24 battery is pretty small, only about 65 amp hours of total capacity, and only about 60% is usable, so you are limited to consuming about 80 amp hours per night.

Your RV will consume 35 amp hours a day just running the CO, Propane detectors and the refrigerator. Anything else is more amp hours, like lights - 1 amp hour per light per hour. Furnace at about 7 AH per hour. water pump is sort of insignificant load, able to pump 120 gallons of water only consuming about 7 AH.

SunElec.com has solar panels for close to $1 per rated watt. You want something with a frame, and 12 volt nominal is preferred. It will be around 20 - 22 volts 'open circuit' with no load on it, and my 120 watt panels will produce about 35 AH daily each.

Unless you expand your battery bank, 300 watts is about the limit to what you can store in the small batteries. You would be able to consume a lot of power on a sunny day, and still not be able to store it all with a 300 watt system. Yet your battery will be 100% full at the beginning of your trip, something that is very important. And very close to 100% full at the end of every day.

Mounts? Home Depot. Get about 2' of 2" angle aluminum. Cut into 6" long pieces, and drill 3 holes 3/16" in the roof side for #10 screws into the roof. 5/16" hole for a 1/4-20 bolt into the solar panel frame.

Controller? I like the PWM because of the cost. A 20 amp controller will handle about 300 watts of panels, you can get two - they are very cheap.

If the 'short circuit' amperage rating is say 7 amps, you can use 2 on a 20 amp panel. 6 amps, and you can use 3 per panel. It would be possible to get more than 6 amps from a 6 amp panel, if you are at a higher altitude (like 5,000' elevation) and there is snow on the roof, the panels are tilted south and get a reflection off the snow.

I don't tilt my solar panels anymore. It is not worth it, the risk to roof problems makes it not worthwhile, besides it is another 'chore' like putting the awning away before moving the RV.

It would only cost another $75 to upgrade the solar system, and that is less than a problem with the roof might cost.

I used #10 UV rated romex (grey stuff at Home Depot) to run from the panels to the controller. Down the refrigerator vent, to my nearby closet where the controller was mounted, then to the battery with #8 wire.

Good luck!

Fred.

Call ahead and stop in Norco on your return. (save the shipping)

https://www.solarblvd.com/index.php?cPath=1_269

I recommend a pair of 120 watt panels and Morningstar PWM controller. Maybe some parallel MC4 connectors and 80' #10 MC4 wire to bring power down.

Here is a simple flow chart.

Budget-->Energy Audit-->Battery bank size-->number of watts-->PWM or MPPT. What ever type of controller is chosen, make sure it has adjustable set points and a temperature probe that is on the battery.

One rule of thumb is between 60 and 150 watts of panels per 100 amp-hours of storage. The smaller the battery bank the higher the wattage needed (per 100 amp-hours). Here is a link to the rather special spreadsheet which includes an energy audit, that N8GS has created to help size solar battery charging systems!

Solar Spread Sheet N8GS

For a nice explanation of solar, try this link:

Golden rules of solar

This is what is balanced and best for twin twelve volt batteries.



As it often doesn't cost a dime more to do this, I think it is worth the trouble.

If you wish to understand the "why" surf here:

correctly interconnecting multiple twelve volt batteries

Others may say it doesn't matter--but unless there is a compelling reason to not optimize charging and discharging why not do it the best possible way?

Here is a video of 3 twelve volt batteries that have been wired in an unbalanced manner for 2 years. They have been equalized. The test shows how CCA has been adversely affected.

unbalanced for 2 years

For only two batteries 150 watt panel should be OK. For hard core solar you will need a lot more of both panels and batteries