Battery backup system

[dunay]

Hello,

I'm designing a PV system to charge batteries.  My house is attached to the grid, but the power goes out frequently, and I would like the security of a battery bank.  The PV system is only going to power a few circuits in the house.

Here is my question:  is there a way to charge my batteries with the grid if my loads out strip the PV electricity?  For example, if the batteries fall below 60% charge, is there a device that could add grid power to boost batteries back up to 60%, and hold them at that level until more electricity could be gathered from the sun?  

I believe my inverter will not allow the batteries to be discharged past a set level.  Is there a device that would connect grid power to my loads once my inverter stopped pulling power from my batteries because their charge was to low?

Thanks for the help.

[TomW]

dunay;

You don't say what inverter you have. My Outback with the Mate does all that. kicks on to grid to feed loads and charge battery bank to keep it within limits you set. Can even tell it when to use grid based on time of day.

Just what I do here.

Winter storm here booting 75 to 300 watts into the batteries all day from my Zubbly Conversion and probably will all night. Push my bank up to a good voltage for a change. Sorry just had to share that.

Cheers.

TomW

[Volvo farmer]

You also don't say whether this must be an automated system or whether you are willing to manually do something when your batteries are low. For a 12V system, a cheap solution might be an automotive battery charger, switched on manually, when necessary.