What size of solar panels are needed to keep battery charged for a few days of boondocking.

Rule of thumb, 100w with the caveat you are not overdrawing more than your solar panel is charging.

Solar wattage needed depends on how many watt hours you burn and is a function of how many amp hours of battery you have. So it’s inappropriate to give a simple number. But I can give you some guidance based upon some assumptions, which you will have to fine tune yourself. If you just have a single 80 amp hour battery as most TTs come off the lot with, AND that serves you well for a day, AND You use no more than the 40 amp hours recommended overnight, then a single 100 watt solar panel will suffice, PROVIDED You get a full day of bright sunshine, and use an MPPT charge controller. To keep that battery fully charged on a cloudy day, you might want two 100 watt panels. If you have a pair of those same batteries, you will probably want 3 - 100 watt panels. If you have a Class A motorhome with a battery bank that runs to 600 amp hours, and you use them to capacity, think something like 600 to 800 watts of solar. I would suggest that such estimates are very much dependent on how much power you use. So my suggestions above are highly dependent on your usage as well as my assumptions.

I have 200 watts of solar with an MPPT controller feeding a 225 AH battery bank (two GC-2 6v batteries). I boondock for weeks at a time and the batteries are fully charged by early afternoon as long as it is not cloudy.

Do an energy use survey...actual or what you’d like to use. Your choice. That determines the battery amp hours needed, which determines the solar watts you need to recharge and the controller size. If you guess, you will be either undercharged or overpaying.“battery charged for a few days of boondocking” is absolutely wrong. A properly sized solar system recharges fully almost every day. Limping along...for a few days? Solar isn’t a new toy or experimental.

It depends on so many variables:Where you camp - cloudy winter northwest to sunny ArizonaWhat time of year - is the sun up high or way down on the horizonHow much TV do you watch, how much music timeAre you going to use the microwave to heat a cup of coffee on batteriesDo you like lots of lights on at nightDo you run the ceiling fansIs it cool out and the furnace blower is working, two furnaces?Lots and lots of variables.An extra couple of panels costs very little overall. The big part of solar is figuring how you're going to install it, where to put the monitors and run the wiring. A little bit larger controller for three or four panels is almost nothing. If your going to go through the exercise, take an extra couple of hours and install three our four panels. (Solar is like horsepower, you never have too much and solar is cheaper than horsepower.)Bill

Solar panels | Good Sam Community

Boon_Docker
Explorer III
Dec 15, 2019
theoldwizard1 wrote:
Trackrig wrote:
It depends on so many variables:
.
.
.
Solar is like horsepower, you never have too much and solar is cheaper than horsepower.

I'll have to remember that last line !

Boon Docker wrote:
I have 200 watts of solar with an MPPT controller feeding a 225 AH battery bank (two GC-2 6v batteries).
I boondock for weeks at a time and the batteries are fully charged by early afternoon as long as it is not cloudy.

I would consider this setup and absolute MINIMUM !

Yeah, a person needs at least 600-800 watts of solar and at least a 500 AH battery bank to boondock for a few days. :B
Johnny_G1
Explorer
Dec 15, 2019
When you boon dock all winter in Arizona you need lots of solar if you want to live like you do at home, Just my thought's.
pianotuna
Nomad III
Dec 15, 2019
This may help:

https://freecampsites.net/adding-solar/
PNW_Steve
Explorer
Dec 15, 2019
Lwiddis wrote:
Do an energy use survey...actual or what you’d like to use. Your choice. That determines the battery amp hours needed, which determines the solar watts you need to recharge and the controller size. If you guess, you will be either undercharged or overpaying.

“battery charged for a few days of boondocking” is absolutely wrong. A properly sized solar system recharges fully almost every day. Limping along...for a few days? Solar isn’t a new toy or experimental.

Good advice.

I have a Kill-A-Watt meter that has been invaluable for getting real world power consumption of my 120v loads. I also have a Trimetric TM-2030 for measuring consumption of my 12 volt and 24 volt loads. The Trimetric will be my onboard battery monitor.
jplante4
Explorer II
Dec 15, 2019
I'm running 4 GC2s with 200 watts of solar on the roof and another 130 watts in a portable panel. I can go until the tanks fill up (about 5 days, but we're not anal about water usage). I do need to run the generator for a hair dryer ;), so I top off the batteries then.
tbax46
Explorer
Dec 15, 2019
I thank everyone for the info. I probably will just be using 12v for 2-3 days for the lighting and igniters. Got some Forest Service campgrounds that are nice for a couple of days.
Boon_Docker
Explorer III
Dec 15, 2019
tbax46 wrote:
I thank everyone for the info. I probably will just be using 12v for 2-3 days for the lighting and igniters. Got some Forest Service campgrounds that are nice for a couple of days.

Something like this 200 watt portable would work good for you if you don't want a permanent setup.

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