Lou, In addition to what Allan said, if you perform the discharge test, measure the terminal voltage across each battery. If you find one battery that drops in voltage more than the others, continue to check/record that voltage over time. This method will expose a weak or bad cell in a series string before the 20 hour test is complete.
Interstate, or any battery manufacturer I know of, will not warrant to replace an entire bank if a cell/battery is defective. Let's talk Interstate batteries. A few year ago they decided to stop selling the high quality, made in the USA, US2200 battery. The import battery that replaced it has a notorious track record for low capacity, low voltage, difficulty charging and short life. I am speaking from experience having analyzed (discharge tests) and diagnosed several dozen small battery systems. One thing I found out, and this comes from an Interstate "Engineer and Specialist", is that the new GC2-HD must be charged daily for 2-4 hours at 2.55 volts per cell. That's 15.3 volts for a 12 volt system. <opinion>I do not know if their L16 comes from the same manufacturer but my opinion is buying Interstate batteries are not worth the risk for the small cost savings. Of course, I say this about any other manufacturer of poor quality batteries.</opinion> Larry Crutcher Starlight Solar Power Systems On Mar 15, 2013, at 2:57 PM, Allan Sindelar wrote: Lou, There is nothing in your message that definitively tells me that you have either a bad cell or a bad battery. "Minor corrosion on one terminal" is normal behavior, especially if the installer didn't coat the terminals at installation. "One cell was not using as much water as all the rest" is a matter of perception. You write yourself that "everything looked fine." It seems to me that you're jumping to conclusions based on the comment of another Wrench without doing sufficient testing first. Get the client to put a measured load on the system without charge. This isn't hard to do with an amp-hour meter in the system - you want a steady load of about 55 A (a C/20 load). If you have a bad cell, it'll show up soon enough. For now, I'm on Interstate's side. Hope this helps, Allan Allan Sindelar al...@positiveenergysolar.com NABCEP Certified Photovoltaic Installer NABCEP Certified Technical Sales Professional New Mexico EE98J Journeyman Electrician Founder and Chief Technology Officer Positive Energy, Inc. 3209 Richards Lane (note new address) Santa Fe, New Mexico 87507 505 424-1112 www.positiveenergysolar.com
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