The only way to do a capacity test is with a load bank over the rated discharge period of the batteries, it they have a 6 hour rate, use that one. The 20 hour rate takes too long! Voltage is a moving target and pretty much useless unless the battery has been sitting with no charge or discharge for 12 hours or so, and all that tells you is the state of charge nothing about the capacity of the battery.
If you are going to buy a load bank the old resistor load banks are the best choices, the newer electronic units are too sensitive to damage and the failure rate is quite high according to my suppliers. They have gone back to the resistor banks in most cases. The load banks can test up to a 48 volt bank at one time, so you don’t need to test each cell for 6 hours, you can spend 6 hours and test them all at once! But your still going to spend 6 hours to do a correct test My first experience with gels was bad enough to make me swear off them and that was 18 years ago. I am sure they have I improved but most of my work is off grid and flooded work best in that use. Later, Bob Ellison From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of North Texas Renewable Energy Inc Sent: Monday, October 04, 2010 9:36 AM To: RE-wrenches Subject: Re: [RE-wrenches] Battery capacity testers Todd I've heard the same arguement, as well as its inverse. The battery choice was the decision of the system owner. I know they are more sensitive to charge/discharge abuse but I see the full charge rate last week at 52.xx V, just like day 1and I trust the Trimetric and the Sunny Islands. We're taking down the entire system to upgrade & install a 400A transfer switch so the batteries will have time to stabilize for the VOC check & cleaning. I guess a more accurate question would be is it good enough to properly check cell VOC and not bother with the discharge capacity check? A compromise could be cap check 12V blocks of cells instead of all 24 separately. Or is the capacity checker a waste of money. Jim ----Original Message----- From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org]on Behalf Of toddc...@finestplanet.com Sent: Monday, October 04, 2010 2:23 AM To: RE-wrenches Subject: Re: [RE-wrenches] Battery capacity testers I know many on this list disagree, but this sounds SO typical for sealed batteries. It is why I never use em... never! If they are 5 years old, you are probably at the limit of their life. Replace em with flooded lead calciums and your customers (and you) will be happy for 20+ years. my .o2 Todd On Sunday, October 3, 2010 9:28pm, "North Texas Renewable Energy Inc" <nt...@1scom.net> said: I have a customer with a set of 24 Concord PVX-6480s that have twice failed during grid outages during the night. No large loads are on the critical load panel and, since it's at night when they drop to 50% dod, I'm not sure what's up with them. I plan on cleaning and retightning all the cable connections first to eliminate that possibility then checking VOC of each cell. Eventually we'll install a 25 kW genset but my first task is to find out the state of the batterys. The system turns five next spring so I don't think they are near an early death. The BOS is 2 Sunny Island 4248s with upgraded chipsets and the charger is set to spec though that may need to be bumped up. The only culprit I suspect is the high summer temperatures in this unconditioned equipment room. Finally it may be time to invest in a capacity tester. What brand is popular among those Wrenches with lots of experience in diagnosing a batterys health? The Concord DC5000 only comes in 12 & 24 V models and these are 2V cells. Thanks as always Jim Duncan North Texas Renewable Energy 486 W.N. Woody Road Azle Texas 76020 NABCEP Certified Solar PV Installer No.31310-57 TECL 27398 nt...@1scom.net 817.917.0527 www.ntrei.com <http://www.ntrei.com/> Sent from Finest Planet WebMail.
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