Adding to an existing battery bank [RE-wrenches]

[Tom Elliot, Guffey Energy Works]

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The first suggestion I'd give you is, you guessed it coming from me, use a 
buss bar.  4 strings won't present a problem if you do that.  When you do 
decide to put in a buss bar I don't see any need to break up the existing 
strings because each individual string will contribute what it can and not 
negatively impact the new strings.

Tom Elliot

----- Original Message ----- 
From: "Dan Rice" <danrice at scinternet.net>
To: <RE-wrenches at topica.com>
Sent: Sunday, June 19, 2005 5:07 PM
Subject: Adding to an existing battery bank [RE-wrenches]


>
> Esteemed Wrenches,
>
> Gubment job, to include doubling an existing, one year old battery bank of 
> 8
> Trojan L-16 G's (two strings of four -24 VDC nominal system) -final
> configuration will be 4 strings of 4 (I recommended against doing 
> this...).
> The site is an existing Nat'l Park Service administrative site, complete
> with 20 kW propane generator, stacked 4024's, and an 1800 Wp array. Mostly
> summer time use; mothballed during snow season. 5-6 kW-h/day use when
> occupied.
>
> Question: what would be the least potentially problematic battery bank
> reconfiguration? Should the existing strings be left intact, and the new
> batteries be installed in two strings? Or, should the existing strings be
> broken up, and made up into 4 new strings consisting of two old and two 
> new
> batteries in each string? I'm inclined to do the latter, to balance the
> resistance of the parallel strings, but I'm not sure if that matters and 
> if
> that might introduce another type of problem that I'm not aware of. As an
> aside, have others come across multiple string banks in which the cell
> closest to either the positive or negative end has deteriorated faster 
> than
> the other cells? If the strings are broken up, should the new batteries be
> on the ends of the strings, leaving the year olds as the center two in 
> each
> string? What is the failure mechanism that attends adding new batteries to
> old? Is it primarily related to uneven string currents causing accelerated
> and uneven wear?
>
> The Park Service is already aware that this battery bank configuration is
> not optimal, and is planning to upgrade to industrial batteries at the end
> of this set's life, but for now they need additional capacity and the
> existing battery set is only a year old. They're hoping to get 3-5 years 
> out
> of this set.
>
> As always, your collective experience is much valued and appreciated.
>
> Dan Rice
> Abundant Sun, LLC.
> 435-826-4565
>


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