Adding to an existing battery bank [RE-wrenches]

[Matt Tritt]

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I second Dan's motion. Mixing the strings wont gain anything and might 
actually be a detriment to the system as a whole.

Matt T

Tom Elliot, Guffey Energy Works wrote:

>
> 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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