6mo old Batteries not holding charge/running down too fast.

[cmlarsen]

About 6 months ago I installed a small battery/charger setup in my cabin (in which i live full time) but I am not getting the performance from my battery bank that I would expect. The batteries run a Flojet RV 12v ondemand water pump for the faucet (about 6 amps) and some 12v CFLs (about 0.8amp each) and some LED lights about .2 amp). The normal draw is about 2-3amps, but I am seeing the battery drop from a full charge to about 70% on my Midnite solar battery capacity meter in as little as two or three hours. The batteries are charged from a 55amp PowerMax AC charger running on a Honda EU2000i. There is no Solar in this system yet, we are building as we go and would like to introduce a PV array at a later date.

Setup Details.

• 4 Duracell GC2 (6v 215 ah (Sam's Club Special) wired in series and then parallel on a aluminum bussbar giving a 12v 430ah system.
• A PowerMax 55amp charger. All of the wiring connections are 4guage jumper cable with solidly crimped ends.
• The charger is hooked up full time and we run the generator for about 2-3 hours per day.
• We've never run the batteries below 50% and they are kept warm (~70F) and the water level is right.
• I have never equalized them.
• There are no phantom draws.
• Left unattended the batteries appear to hold a charge, they just run down much faster than I think they should.

I've attached a wiring diagram.
cabin-wiring-diagram.gif

My math would say that if i have 430 amp hours, and i draw 3 amps an hour for 5 hours on a fully charged battery bank I would consume 15 amp hours in that period, leaving my batteries with 415 amp hours or 96% health. But what I am seeing (on my meter and with measuring the voltage with a mulitmeter) is more like 70% or 80%).

So, is there a problem, what might it be, and how can i fix it

[Sunking]

What voltage are you seeing to determine SOC?

[cmlarsen]

What voltage are you seeing to determine SOC?

I am seeing 12.7-12.8 for a full charge and last night after about 4 hours of drawing 3amps i was seeing 12.5v

[Sunking]

So what is the problem?

The only way to accurately use a volt meter to measure the SOC of a battery is to disconnect it and let it rest for several hours. 12.5 volts on a rested open circuit battery is roughly 85 to 90% capacity. On a loaded or charging battery means nothing.

The only way to get the real SOC is with a temperature compensated hydrometer which any battery user should have and know how to use.