AGM battery strings: Problems? [RE-wrenches]

[Kelly Keilwitz]

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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