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 wa...@pureenergysolar.com http://pureenergysolar.com 352 377-6527 Office 352 336-3299 Fax 352 316-1637 Cell The content of this message is Pure Energy Solar Confidential. If you are not the intended recipient and have received this message in error, any use or distribution is prohibited. Please notify me immediately by reply e-mail and delete this message from your computer system. Thank you. Date: Tue, 31 May 2011 18:16:56 -0600 From: al...@positiveenergysolar.com To: re-wrenches@lists.re-wrenches.org Subject: Re: [RE-wrenches] 24 volt Battery Bank comparison Tom, Yes, but if you use individual 2V cells, you can pull one failed cell out of the string and get by just fine by adjusting setpoints down by 8% (11/12ths). You'll lose 8% of capacity until a cell is replaced; or, if the failed cell is the first to go at end-of-life, just live with the remaining 22V bank while collecting funds for the replacement set ("You have been setting aside some money each year for that set, haven't you?"). Using two strings is fine, but if the smaller strings are made up of 4V or 6V cases, you no longer can remove just one cell. Rather, you must disconnect one string and live on 50% capacity (or 67% with two out of three strings) until a replacement is secured. Based on the above, I'd usually go with a single string of the best batteries I can find. Personally, I like what Chris Worcester wrote: My one string of 1476 AH IBE 2 V cells went 19 years before retiring them to a neighbor’s off grid system, where they are now working. One string has my vote! as I just put that exact size of IBE 2V cells in my own home. Here's hoping I get another 18 years and 10 months out of them. Allan Message body Allan Sindelar al...@positiveenergysolar.com NABCEP Certified Photovoltaic Installer NABCEP Certified Technical Sales Professional New Mexico EE98J Journeyman Electrician Positive Energy, Inc. 3201 Calle Marie Santa Fe, New Mexico 87507 505 424-1112 www.positiveenergysolar.com On 5/31/2011 5:36 PM, Tom Elliot wrote: From a reliability standpoint I would never want to bet the farm on one string. All it takes is the failure of one cell and the system is useless until it is replaced. Three strings means a cell failure only reduces capacity by 33% not 100%. I’ve always thought in off-grid systems it is a good idea to build in as much redundancy as possible whenever possible. Oh, and always use a buss bar system with multiple strings, it makes for a far more stable system with less stress on the batteries. Tom _______________________________________________ List sponsored by Home Power magazine List Address: RE-wrenches@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
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