[RE-wrenches] 5 battery strings

[Tom at wagonmaker]

This was 22 years ago and I got my buss bars from a battery distributor who did large backup installations for telco systems.   He was horrified that we in the business were paralleling series strings together in a daisy chain.  Said it was the best way to give batteries an early death.  I had a source but last time I posted it I was told it was no longer in business.  But I would think anyone who installs systems for large battery backups, either for wind systems using containers full of batteries or telco backup power, would have access to a good source.  I preferred tinned copper bars.

Using buss bars allows for creating banks of lots of batteries which allows for redundancy.  I’ve never understood why you would want to put all your eggs in one or two baskets, so to speak, by paralleling two series strings of large batteries.  One cell in one battery failing kills half the storage right off the bat and the system has to be taken offline just to remove the defective string.  With a buss bar there is no interruption of service, batteries can be swapped out easily while the system hums along.  My AGMs were solid for years and very well balanced.

Tom 

From: Chris Schaefer 
Sent: Monday, July 23, 2018 8:28 AM
To: RE-wrenches 
Subject: Re: [RE-wrenches] 5 battery strings

What source are you all using for buss bars for these multiple battery string set ups? 

Christopher

On Mon, Jul 23, 2018 at 2:16 PM, <tom at wagonmaker.com> wrote:

  Separate out the individual series strings and run each string to a buss bar setup.  Remember it isn't just resistance differences between batteries but resistance difference between cells as well.  In a setup like the existing one the resistance differences can really add up and if one battery fails the entire system will be offline.  Running each string to a positive and negative common buss bar means you can remove individual strings without disrupting the entire storage and the system can continue operating.  Also, it means the only resistance issues of substance are within individual series pairs not the entire interconnected bank.

  I ran 10 series pairs of 12v AGM batteries, each pair to a common buss and it was the longest lasting, most stable battery bank I had.  That was years ago and now it would require fusing each string but for longevity and stability it is the best bet.

  Tom

  On 2018-07-23 03:56, Dave Tedeyan wrote:

    Since we are on the topic of bad battery practices...

    I may be fixing up a system that was both designed and installed very
    poorly.
    They have a 24V Outback VFXR inverter, and ten 12V AGM batteries wired
    into
    5 parallel strings. I know that is a bad idea, but since they already
    have the
    equipment, are there any safety issues by re-using this equipment? It
    is for a
    grid tie battery backup system that will remain in float most of the
    time. I assume
    that the batteries will not last particularly long, but is there any
    harm in using them
    and then just getting new batteries once they fail?

    Stringing is shown in the attached picture.
    Cheers,
    Dave

    --

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Chris Schaefer’s

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