5 or 10W panel to keep generator battery charged

porch13 said:

I'm purchasing a home that has a Generac generator that runs the well pump.  The previous owner had issues with the generator battery losing charge between uses of the well.  I'd like to as a small panel to the roof of the building to keep the battery topped off.  The battery is a 12V with 675 cranking amps / 540 cold cranking amps.  NAWS carries both a 5 and a 10 watt Solartech panel.  Would the 5W be sufficient if I get plenty of sun? 

I would get a bigger panel, maybe a 100 watt panel and a charge controller.
A 100 watt panel will give about 5 amps.
I would hook wires and a switch to the battery and run a 12 volt LED light of the same battery also. This way you would have a light in the well house/ generator house if needed.

If the genset doesn't run often enough to keep the battery healthy (like your car) I would suggest:

1) Use a battery that has a low self-discharge rate like 1% or 2% per month instead of 7.5%-15% or more per month. That is not a large battery so the additional investment over a cheap battery won't break the bank.

2) Add a low current float charger via solar that will hold something like 13.5v. That will hold the battery steady indefinitely. It is important to realize that you will destroy the battery prematurely if the voltage isn't properly controlled. Some cheap solar kits are uncontrolled.

Marc

Porch, you may want to check the wiring connections for the battery in the generator. I had the same problem, battery was losing charge. I discovered that my electrician overlooked connecting the generator's built-in charger designed to charge the battery from house wiring. 

If you do not have the generator operators and/or the installation instructions, then I would go online to see if your model Generac has such a feature. If so, maybe another option for you.

Paul
in Georgia