battery maintainer.

Some suggestions (as always, I am NOT a battery engineer).

Plan on at least 1% to 2% rate of charge for an old/just about ready to recycle/ battery bank. Newer/batteries in good condition will have a float charge less than that.

If your float is 2% or greater--Time to recycle the battery. Lots of wasted energy, and the battery runs the risk of "interesting" self destructive events (overheating, etc.). The higher the float current (>2%, the more chance of a "bad" event).

The other thing to look at is how much electricity is this costing (either off grid charging, or from your utilty)... A 2% rate of charge:

• 27.0 Volts float * 510 AH * 0.02 rate of charge (worst case) = ~275 Watt (DC) load to float (worst case assumptions)
• 275 Watts * 24 hours per day = 6,600 WH per day (6.6 kWH per day)

Obviously, at 2% float charging current (assuming battery near failing), that is a lot of extra power to keep the battery around for "Just in Case" usage.

Anyway--My suggestion is to measure the steady state charging current (and voltage) and/or put a kill-a-watt meter on the AC float charger and see how much it really draws... If it is "significant (approaching 1% or higher float current)--Probably not worth keeping around.

Another way is to charge to "Full", then let it sit and check the SG (say once per week). And when it gets down to 75% SoC--Recharge. A "good battery FLA bank" should go 1 month between charges... That amount of energy would be:

• 14.5 volts charging * 510 AH * 25% depth of discharge = 1,849 WH = 1.85 kWH (per month?)

Again, assuming bank goes "1 month between charges", and you are willing to put ~2+ kWH (including losses) into keeping the bank in standby.

Anyway, some "math" to try and get data to make your decision.

-Bill