solar battery needs/ requirements

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

gocamping14 wrote:
thanks for the replies. I have two new 12 batteries at present and would like to connect them together to save $ if possible. my main needs are for gas refrig. and minimal lights. have a generator to use if needed.

ss

HI,

I have a e-meter on my motorhome that carefully tracks my battery useage. It shows that I consume 35 amp hours daily just to run the CO meter, propane detector and refrigerator. So don't think that because you do not run any lights at night that you will not need a large battery.

It takes a 120 watt solar panel to make up the 35 AH daily in my RV. Then lights and furnace will require more power.

I installed a 90 watt solar system on a small class C - 1985 without the power hungry CO and propane detectors. Also the refrigerator did not use 12 volt power, or have that front display that is so easy to use. After upgrading to a Bounder RV, I found I needed a 75 watt panel. Later I installed a pair of 120 watt panels.

I liked to watch a lot of TV and satellite TV. I have 4 golf cart batteries, 440 AH capacity. I could use 120 AH overnight and still fill the battery by sunset.

I would recommend at least a 120 watt panel, then upgrade if you like from there. A 140 watt was for sale at this place for $229 a few weeks ago.

SunElec.com

For mounts, I cut off 6" long 2" angle aluminum with 3 holes into the roof and 5/16" hole for a bolt into the solar panel frame.

For wiring, I bought #10 UV rated grey romex from Home Depot. I ran mine down the refrigerator roof vent, to the controller, and to the battery.

Good luck,

Fred.

Most of us find that what we thought was enough wasn't. We went from 160 watts of panels and supposedly 300 AH of battery (4 group 24 marine/deep cycle) to 420 watts of panels and 484 AH of battery. We could use another couple of hundred watts of panel.

Besides the energy audit I have two specific recommendations:

1) Use a wire gauge capable of at least twice the current you plan to get from your panels. Makes it much easier to upgrade later.

2) Mount the controller as close as possible (a few feet) to the batteries with as large a gauge wire as possible without being stupid about it. (4/0 cables with for 10 amps of current is just plain silly and a waste of money) You can afford to loose a few tenths of a volt between the panels and the controller but NOT between the controller and the battery. If you must skimp on wire size do it on the input side of the controller.

Easy... 200 to 300 watts and a programmable controller.

Do you have any local suppliers to save shipping?

thanks for the replies. I have two new 12 batteries at present and would like to connect them together to save $ if possible. my main needs are for gas refrig. and minimal lights. have a generator to use if needed.

ss

X2

coolmom42 wrote:
There is a great SPREADSHEET CALCULATOR here that will help you accurately size your system---not just guess at it.

Get 2, 6-volt Golf cart batteries, connect in series. You'll be glad you did.

Provided space is not an issue, 6v Golf Cart batteries are likely your best bet. Unless of course, they will be in doors, and not ventilated; then a good quality truly deep cycle AGM battery would serve you well. And then there's LiFePo4... but only worth the cost if full time dry camping.

Bank size, as well as Solar system will depend on your demands and habits.

List what you have in the way of equipment, and what you expect to use, power wise, for more detailed answers.

There is a great SPREADSHEET CALCULATOR here that will help you accurately size your system---not just guess at it.