Re: [pvusers] Battery Time

[Michael Welch <michael.welch@homepower.com>]

Bill Schudlich wrote at 06:54 PM 11/11/2002 -0800:
  
>I want to ask a couple battery questions.
>
>I'm working off 10 6v ~350AH Interstates right now, wired for 12v.  6 years old, and I think they're about done.  Did an eq charge this weekend, and still only maxed out at 12.2v

Hi Bill. This doesn't make sense to me. Usually when your batteries are weak, the voltage goes up high and fast during equalization. What is the voltage after equalizing, no load, and the batteries have rested awhile? And then under load?

Unless you discharge them too deeply and they don't get charged up again soon, I think 6 years isn't long enough. I would be bummed not to get 8-10 years out of a battery. But then, I am one of those folks that freaks out when my batts hit under 70% of capacity.

>I'm seriously looking at the Concordes.
>
>Does anyone have experience with AGM batteries?  Upside/downside compared to lead-acid in terms of performance?

Personally, I prefer flooded cells, though I have never run AGMs. They hold more energy per pound and per dollar. And a biggie is that they are more forgiving of less than ideal charging-discharging routines. And, they are easier to equalize if some of the cells are underperforming.

>Our batteries are stored in an insulated, but unheated shed, which isn't a problem 99% of the time.  Occasionally, I'll have to run a kerosene heater in there when a nasty front rolls through. Looks like the AGM batteries have a wider temp range, but I wonder what the drawbacks are.  Cost appears to be close enough to consider it (especially after adding the maintenence headaches).

Freezing is most harmful to any L-A battery when they are discharged. Not 100% sure, but I have heard that a full L-A battery will not freeze due to the high acid levels. Anyone verify that?
  
Michael Welch
  
------------------------
"The only nuke plant we need is already 93 million miles away."
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Michael Welch, michael.welch@homepower.com
     Home Power magazine
     www.homepower.com
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