[RE-wrenches] Deka AGM (was Small battery bank vs too large array:

[Larry Crutcher, Starlight Solar Power Systems]

Vince,

I know of no such "vulnerability". In fact, an AGM can provide much more instant current than any flooded battery. Concorde (Lifeline, SunXtender, etc.) and Fullriver AGM's are very robust designs. On the other hand, Deka AGM's, specifically the 12 volt 8A8D, are not to be trusted at all. We have stopped selling all Deka/MK AGM's due to very high failure rate.

One other point to consider, having 5 parallel strings of 12 volt batteries is generally asking for short battery life, especially with an AGM since you can not check the SG to be sure all are charged fully. Cells do not charge at the same rate and having parallel paths for current will leave some cells deficit charged. Having many parallel strings exacerbate this issue. If you do upgrade the bank, opt for lower voltage, higher capacity batteries.

Larry Crutcher
Starlight Solar Power Systems
(928) 342-9103


Just a word of caution on the AGM batteries. AGM's do have some vulnerabilities compared to deep cycle wet filled batteries. We had a bank of 20, 8A8D  running a Buddhist Retreat compound and were unable to convince our clients that there were limitations to the amount of power that they could run at one time. They managed to overheat and destroy the whole bank of batteries we think by using too much power during a retreat camp. People had brought there own appliances to use at the camp and we still don't know what the total load was on the 4, Outback VFX 3648 inverters. I'm guessing it was up there close to the 14.4 kW limit of the Outback inverters. We also petitioned our client for a larger battery bank but they didn't think they would ever need that much power. 

-- 

-- 
Vince McClellan
Energy Design 
www.solarenergydesign.com
p: 541.485.8122; f: 541.338.3168  
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