Easy battery question

[jefffoxsr]

I am trying to figure out how much current is required to maintain the charge of my single group 27? RV battery over the winter.

I want to buy a solar panel of the proper amperage.

There is a 5 watt panel that I have that is 350 milliamps at 24 volts in bright sunlight. I measured it at about 16 volts when the sun is behind the clouds. I don't know how to figure out how many milliamps that would be at 16 volts.

Assume 7 hours of daylight with most of those days being cloudy in the winter here.

How many milliamps per cloudy day would be put into the battery with this 5 watt panel and would that be enough to maintain the single standard group 27?

If the 5 watt panel won't be enough then can you tell me what wattage would be the minimum wattage panel adequate to maintain the battery?

Thanks.

[time2roll]

5w in winter? Maybe in the south.

[B_O__Plenty]

Why not just take it out and eliminate the possibility of an electrical malfunction? You can charge it home once in awhile or put a battery maintainer type charger on it. Lots cheaper and you know it will work.

B.O.

[hmknightnc]

If your opening your battery disconnect (or disconnecting the battery) a 5 watt panel with no controller on a GP27 will be fine. It will just make up for battery internal losses which all you need for that kind of service.

If your thinking about what it takes to have useful actual recharge capability then you need to be thinking 85Watts with controller and up depending on power needs.

[pianotuna]

Hi,

A flat install of a 15 watt panel would be safe. Anything more and a charge controller may be necessary.

[RCMAN46]

As per optima if voltage is between 13.2 and 13.8 and less than 1 amp you can go for an indefinite time.


Battery

[Swamp_Man]

Jeff,

The solar panel isn't that important as long as it will put out at least 100 watts. What is important, is the controller charging the batteries. If you over charge the battery, you are faced with a dead battery. Same thing if you under charge it. Check the sites on solar charging to find a charger for your RV that has a maintenance charge cycle.