I sent this thread to Rob Shappell of NWES Battery. Here is his .02. Dana Orzel
Great Solar Works, Inc www.solarwork.com E - [email protected] V - 970.626.5253 F - 970.626.4140 C - 970.209.4076 I will be the shift in how the world uses power! - Dana Orzel -----Original Message----- From: Rob Shappell [mailto:[email protected]] Sent: Thursday, December 03, 2009 8:15 AM To: 'Dana' Subject: RE: [RE-wrenches] Strings and series of batteries Hi Dana, It's all about even distribution of the energy whether the battery is being discharged or recharged or no load at all. 2 parallel strings are do-able an usually don't cause any problems, 3 strings or more however, is where the problem of un even charging and discharging starts to show up, and aging batteries amplify the problem. With 3 or more parallel strings we recommend both, the buss bar and paralleling at the battery. Remember that 5 Parallel battery we worked on for the owners of gas wells? The cabling was very extensive, but I still expected problems down the road. Nothing that would void the warranty, but problems none the less. In any parallel setup, voltage will seek the lowest voltage bank and current is always flowing until all banks are equal or drained. You only have the capacity of the weakest cell/bank. Batteries are man made and are not as consistent as the timeless laws of energy. -----Original Message----- From: Dana [mailto:[email protected]] Sent: Wednesday, December 02, 2009 7:40 PM To: Rob Shappell Subject: FW: [RE-wrenches] Strings and series of batteries What's your opinion on this Rob? Dana Orzel Great Solar Works, Inc www.solarwork.com E - [email protected] V - 970.626.5253 F - 970.626.4140 C - 970.209.4076 I will be the shift in how the world uses power! - Dana Orzel -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Michael Welch Sent: Wednesday, December 02, 2009 5:00 PM To: RE-wrenches 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: What's up with that? If it helps make charging equal, is it worth the extra expenses and connections involved? http://www.green-trust.org/wordpress/wp-content/uploads/2008/09/cross-tied-b attery-bank-300x187.jpg 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: [email protected] 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: 270.14.87/2536 - Release Date: 12/02/09 00:33:00 No virus found in this incoming message. Checked by AVG - www.avg.com Version: 9.0.709 / Virus Database: 270.14.87/2536 - Release Date: 12/03/09 00:32:00 _______________________________________________ List sponsored by Home Power magazine List Address: [email protected] 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
