[RE-wrenches] Strings and series of batteries

Wed Dec 2 20:33:08 PST 2009

Michael,

There are 12  1/0 cables running from the batteries for each side of the 
buss, pos and neg plus the two 4/0 cables.  There are 12 series strings in 
that 24v system wXH consisting of two 12 volt 100-amphour DCS-100L Dynasty 
deep cycle AGM batteries.  That system has so far been in place for 6 years 
and is rock solid.  We've since sold the house but my last two annual 
checkups (which I don't do anymore) showed nothing great than a 1/10 volt 
difference between the individual 12-volt batteries throughout the bank. 
I've replaced one cable which is incredibly easy (as easy as working with 
batteries ever gets anyway) and required no shutting down of the system.

It's been a while since I had the engineering discussion with the Dynasty 
engineer who spec'ed these batteries for me and reiterated what I'd already 
been told about using buss bars by the wholesaler I used to deal with.  I 
suspect Jamie can give a better technical explanation but I do recall he 
said that while the virtual circuit looks the same in a diagram the behavior 
of the system is different using the buss.

Tom

--------------------------------------------------
From: "Michael Welch" <michael.welch at re-wrenches.org>
Sent: Wednesday, December 02, 2009 5:05 PM
To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
Subject: Re: [RE-wrenches] Strings and series of batteries

> Thanks, Tom. I think I have seen those photos before.
>
> Am I seeing 16 cables hooked up to each bus bar? Are you using 2 cables 
> for each end of each string? Is that 8 series strings?
>
> I can certainly see the advantage of being able to easily remove a string 
> from the system.
>
> But I still do not see how it will treat the individual batteries much 
> better than using large parallel cable interconnects, which might be 
> cheaper if the runs are not too long.
>
>
> Tom Elliot wrote at 06:45 PM 12/2/2009:
>
>>Michael,
>>
>>Here are photos of how it's done in a home situation 
>>http://www.wagonmaker.com/newbatt2.html
>>
>>What is handy about the buss bar is the ability to use much smaller cable 
>>from each series pair (in this case) to the buss bar, thus less expense in 
>>cables than otherwise and additional expense for the smaller cables is far 
>>better if it produces extended battery life and ease of service than the 
>>alternative.  The buss bars themselves are tinned copper bars mounted on 
>>stand-offs.
>>
>>Thanks to Jamie Surrette for confirming the wisdom of such setups.  I 
>>would love to see battery companies beginning to provide hardware for such 
>>systems and educating installers on how to use them.
>>
>>Tom
>>
>>
>>--------------------------------------------------
>>From: "Michael Welch" <michael.welch at re-wrenches.org>
>>Sent: Wednesday, December 02, 2009 2:00 PM
>>To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
>>Subject: Re: [RE-wrenches] Strings and series of batteries
>>
>>>
>>>I wish I understood this bus bar use better. Electrically, these seem to 
>>>be the same thing. But by using the bus bar, there has to be more cables, 
>>>cable ends, and connection points. And cost.
>>>
>>>I just drew a battery bank (see below link to graphic), three series 
>>>strings in parallel. On the negative side I drew a bus bar. On the 
>>>positive side I drew normal parallel cable interconnects.
>>>
>>>The bus bar side requires 3 cables with 6 cable ends and 6 
>>>interconnection points.
>>>
>>>The cable side requires 2 cables with 4 cable ends and 3 interconnection 
>>>points.
>>>
>>>How can a bus bar possibly be better? There will always be one more 
>>>cable, and 2 more cable ends to connect.
>>>
>>>I do not see how either way could cause the current for one battery pass 
>>>through another. It is merely using the terminal of the battery as a 
>>>connector between two cables. Ditto for any difference in how internal 
>>>resistance reacts, they both seem the same to me.
>>>
>>>Related question #2:
>>>
>>>It also has been noticed that some installers use "cross tie" 
>>>interconnects for paralleling batteries in the middle of the series 
>>>strings where the positive of one battery connects to the negative of the 
>>>other -- not just at the final pos. and neg. outer ends of the strings. 
>>>In fact, some even recommend two cables between:
>>>http://www.green-trust.org/wordpress/wp-content/uploads/2008/09/cross-tied-battery-bank-300x187.jpg
>>>
>>>What's up with that? If it helps make charging equal, is it worth the 
>>>extra expenses and connections involved?
>>>
>>>Here is a little jpg that illustrates both of these questions:
>>>ftp://ftp.re-wrenches.org/pub/bbvscablewcrossties.jpg
>>>
>>>
>>>
>>>Tom Elliot wrote at 02:19 PM 12/2/2009:
>>>
>>>>Darryl, The process of paralleling through buss bars means attaching 
>>>>each serial string to a pair of buss bars rather than to neighboring 
>>>>series pairs so batteries aren't passing current through each other and 
>>>>aren't affected by each others internal resistance.  The buss bars then 
>>>>feed the inverter breaker.  It's standard practice in large telco 
>>>>installations which is where I got clued into the process.  I got some 
>>>>batteries from a wholesaler who did those installations and he was 
>>>>aghast at the idea of series/parallel installations the way off-grid 
>>>>systems have been done traditionally.
>>>
>>>
>>>_______________________________________________
>>>List sponsored by Home Power magazine
>>>
>>>List Address: RE-wrenches at lists.re-wrenches.org
>>>
>>>Options & settings:
>>>http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>>>
>>>List-Archive: 
>>>http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
>>>
>>>List rules & etiquette:
>>>www.re-wrenches.org/etiquette.htm
>>>
>>>Check out participant bios:
>>>www.members.re-wrenches.org
>>
>>
>>
>>>
>>>No virus found in this incoming message.
>>>Checked by AVG - www.avg.com
>>>Version: 9.0.709 / Virus Database: 270.14.90/2540 - Release Date: 
>>>12/01/09 21:33:00
>>_______________________________________________
>>List sponsored by Home Power magazine
>>
>>List Address: RE-wrenches at lists.re-wrenches.org
>>
>>Options & settings:
>>http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>>
>>List-Archive: 
>>http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
>>
>>List rules & etiquette:
>>www.re-wrenches.org/etiquette.htm
>>
>>Check out participant bios:
>>www.members.re-wrenches.org
>
>
> _______________________________________________
> List sponsored by Home Power magazine
>
> List Address: RE-wrenches at lists.re-wrenches.org
>
> Options & settings:
> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>
> List-Archive: 
> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
>
> List rules & etiquette:
> www.re-wrenches.org/etiquette.htm
>
> Check out participant bios:
> www.members.re-wrenches.org
>

>
> No virus found in this incoming message.
> Checked by AVG - www.avg.com
> Version: 9.0.709 / Virus Database: 270.14.91/2541 - Release Date: 12/02/09 
> 09:43:00
> 