Not surprised at all about the phone company guy. It was a phone company guy who read me the riot act that no one in their right minds would ever parallel battery banks the way PV off-grid systems did and got me to set up my system with separate strings connected independently to buss bars. The battery engineer I talked to years ago at Dynasty not only said the same thing but also said keeping strings separate meant individual string distance from the bars became irrelevant (given correctly sized wire for each string’s parallel connectors). I had a system with 12 100 amphour strings of paired 12v Dynasty AGMs which was rock solid until the day I sold the house. The last time I checked the system before the sale no single battery varied from any other in the system by more than 1/10 volt and the majority were still holding identical voltages.
From: d...@foxfire-energy.com Sent: Wednesday, June 01, 2011 4:14 PM To: RE-wrenches Subject: Re: [RE-wrenches] 24 volt Battery Bank comparison Good thread. Thanks. In my experience, it all boils down to the customer. I've seen one temp. set up with like 12 strings (for a concert). but they were recharged and sold individually within a few weeks.. I've also seen a single string (Teledyne aircraft batteries) fail in less than a year.. they were in a brand new airplane tug that was never charged -- ever. (the guy said "I dunno, it just stopped working"). I have one customer who (last I knew) was running 6 strings of mixed aged L-16s going on 8 years. Thing is, he's a retired phone company dude (Who's missing half of his right hand from using one of those pocket pal screwdriver thingys on a key chain in a hot DC rack.. like he'd done hundreds of times before.. but that's another tale). But I do like his set up.. he has each string set up with it's own fused Disco and Trimetric.. Gives him random control over each string. And yes, he keeps a very detailed log, and you can bet that when he takes a battery out of service, it's done. Me? for an average bullet proof off grid system, I shoot for a max of two strings for 24V systems (for the redundancy), and manually reconfigure them every few years. for 48V systems, I shoot for one string of two Volt cells.. thinking that if I loose a cell I can still operate a 46V system until I get a replacement. And Yes, as we all know, there are folks out there that really shouldn't be allowed to operate a popsicle stick. db Dan Brown Foxfire Energy Corp. Renewable Energy Systems (802)-483-2564 www.Foxfire-Energy.com NABCEP #092907-44 -------- Original Message -------- Subject: Re: [RE-wrenches] 24 volt Battery Bank comparison From: Michael Welch <michael.we...@re-wrenches.org> Date: Wed, June 01, 2011 1:43 pm To: RE-wrenches <re-wrenches@lists.re-wrenches.org> Every now and then I see reference on this list to the need for thermal detection. Here is an interesting, inexpensive piece of equipment that could be used for finding hot (loose or corroded) connections, hot batteries, hot PV cells in modules, and even poorly insulated spots, its original intended purpose: http://www.blackanddecker.com/power-tools/TLD100.aspx I have one and used it for finding uninsulated spaces, but cannot attest to its durability or suitability for the other uses mentioned above. boB Gudgel wrote at 01:00 AM 6/1/2011: >This might be a good reason for an installer to have one of those FLIR (or similar) thermal imager cameras.  They're a bit on the expensive side, but could >really be helpful for so many things.  Even just to know if you have left a nut loose (under load of course) > >boB _______________________________________________ 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 -------------------------------------------------------------------------------- _______________________________________________ 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 -------------------------------------------------------------------------------- No virus found in this message. Checked by AVG - www.avg.com Version: 10.0.1375 / Virus Database: 1511/3673 - Release Date: 06/01/11
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