[RE-wrenches] 24 volt Battery Bank comparison

[Tom Elliot]

Bob,

I totally understand the concern about multiple strings *if the strings are connected across the battery bank* as had always been the tradition in off-grid installations.  My own experience with such a bank in my system  showed why when I had a single cell get to near meltdown.  I was lucky to find it.  Maintenance is another reason, such banks are far more difficult to maintain.  But I think those concerns are ameliorated a great deal with a buss bar installation and once I did that I never had another problem and found the battery bank much easier to maintain because the strings no longer had to be right next to each other.  Heck, it would be possible to put each series string in its own box for that matter.  And with the inclusion of string fuses that reduces problems even further.  

When living with an off-grid system my biggest concern was system reliability and redundancy and the idea of a single string failure was a big worry which is why I never would consider it.

Tom



From: boB Gudgel 
Sent: Tuesday, May 31, 2011 8:16 PM
To: RE-wrenches 
Subject: Re: [RE-wrenches] 24 volt Battery Bank comparison



OK, I've been hearing for years now that one battery string is best and maybe two but no more should be used.

What is the reason for this fear ???    What is the experience with multiple strings in parallel ??

If it is because of current sharing of the strings, that shouldn't be an insurmountable problem if the wiring is done right.

If it has to do with the possibility of fire, which Darryl mentioned, seems that series string fuses could mitigate the possibility of that issue, if because of shorted cells, just like PV combiners.

Or maybe it has to do with the trouble of getting into the middle of a pile of batteries ?  Use battery boxes ?

The strings are in parallel and so they all get the same voltage, theoretically anyway if the connections are good.

I would think that the more strings, the LESS stress on individual batteries, not more.  The current in each battery should be less than it would be I would think.

So what is the real experience ?? 

Is a battery balancer the answer ??

Thanks,
boB







  On May 31, 2011, at 8:23 PM, "Wayne Irwin" <wayne at pureenergysolar.com> wrote:


    I think the verdict is 12 - Rolls 2-YS-31 2430 AH @ 20 HR (one string) and one dry spare in storage is the best case scenario!

    Wayne Irwin, EE
    Director of Engineering
    Pure Energy Solar International Inc. 
    State Licensed Solar Contractor
    License # CVC56695 
    Wayne at PureEnergySolar.com 
    http://pureenergysolar.com 
    352 377-6527 Office
    352 336-3299 Fax
    352 316-1637 Cell




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