AGM battery strings: Problems? [RE-wrenches]

[Jim Easton]

Sounds like you really want to do this.

I believe you will do no worse than if you just had one.  Unfortunately,
with AGMs you cannot test the electrolyte, so you are limited in your
diagnostics. Putting older, smaller batteries with younger larger ones seems
to me to be a recipe for imbalance.


Jim Easton
Alternative Energy Technologies
CSL: 852243
9465-B Mission Park Place
Santee, CA 92071
Tel: 619-262-8800
Fax: 619-562-8811
Cell: 858-527-0240

-----Original Message-----
From: Kelly Keilwitz [mailto:kelly at whidbeysunwind.com] 
Sent: Friday, December 01, 2006 4:55 AM
To: RE Wrenches listserve
Subject: Re: AGM battery strings: Problems? [RE-wrenches]


Jim,
I know problems are possible, but was hoping that the voltage/resistance of
the two strings will be alike enough that the problems would be minimal.
What's the worse case - that the capacity of the larger string falls to that
of the smaller? We might be willing to put up with that. Or, is premature
failure a real possibility?

This is a grid-tie, hands-off, will-work-automatically-guaranteed, backup
system. So, switching between banks for won't work here.


On 11/30/06 1:02 PM, "Jim Easton" <jim at altenertec.com> wrote:

> 
> Possibility of problems? Yes.
> 
> Paralleling batteries of dissimilar type/history can lead to premature
> failure & lack of anticipated capacity.
> 
> A better solution might be to use an A-B switch with a battery isolator
for
> charging.
> 
> Jim Easton
> Alternative Energy Technologies
> CSL: 852243
> 9465-B Mission Park Place
> Santee, CA 92071
> Tel: 619-262-8800
> Fax: 619-562-8811
> Cell: 858-527-0240
> 
> -----Original Message-----
> From: Kelly Keilwitz [mailto:kelly at whidbeysunwind.com]
> Sent: Thursday, November 30, 2006 8:20 AM
> To: RE Wrenches listserve
> Subject: AGM battery strings [RE-wrenches]
> 
> 
> Wrenches,
> Recent grid outages here have a few of our grid-connected, battery-based
> customers wanting more battery capacity. Two of the systems have Concorde
> AGM's in single, 48-volt strings. I'd like to take the 2-mo old, 104AH
> (24-hr) set from one system and add it to the 6-mo old, 89AH set in
another
> system.
> Do you see any problems with paralleling these different capacity strings?
> Should I cable individually from each string (2+ & 2-), or will simple,
> reverse return (1+ & 1-) flow be sufficient?
> 
> Thanks,
> -Kelly
> 
> 
> Kelly Keilwitz, P.E.
> Whidbey Sun & Wind, LLC
> Renewable Energy Systems
> NABCEP Certified PV Installer
> 987 Wanamaker Rd,
> Coupeville, WA 98239
> PH & FAX 360-678-7131
> sunwind at whidbeysunwind.com
>  
> 
> 
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Kelly Keilwitz, P.E.
Whidbey Sun & Wind, LLC
Renewable Energy Systems
NABCEP Certified PV Installer
987 Wanamaker Rd, 
Coupeville, WA 98239
PH & FAX 360-678-7131
sunwind at whidbeysunwind.com
 


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