Greetings Gary, I like what John and Tump provided for advice on this. They both have a great deal of experience with batteries. I agree some of what John described can produce misleading numbers. The Concorde (manufacturer's) recommended test procedure will take a fair amount of time, but observing actual amp hours "in" (charge) and amp hours "out" (discharge) while observing voltage will give the most accurate results. These are AGM VRLA batteries, so measuring specific gravity with a refractometer as part of testing is not an option. If these batteries are about 9 years old it may be time for their owner to invest in new replacements depending on how well they have been cared for and how much exercise they have, or have not had. Labor time testing and trying to recover these batteries can be viewed as expensive, especially if they end up needing to be replaced anyways. If they were still under warranty the manufacturer's recommended test may have to be performed in order to obtain a warranty replacement. I doubt this is the case with this ~9 year old battery system.
I can look at a case like this in a couple of different ways... Do we want to see if we can find one or two batteries that are causing the issue and try to recover them, or do we need to determine the actual battery system Ah/kWh capacity? Sometimes we need to do both. With a battery bank like this the technician should be able to at least determine if any one or two batteries stand out as being the issue(s) ("weakest link in the chain"). Internal resistance testing is one helpful way to help determine this. Since these are 12V batteries an automotive battery internal resistance tester may be used. If I was troubleshooting this battery system I would take and record voltage and current measurements as the system is. Then I would un-wire the batteries from each other; removing the interconnect cables, fuses, and inverter cables. I would take and record VOC measurements of each battery, ideally after they were at rest for at least a few hours. Next I would use a 12VDC internal resistance battery tester to test each battery. A cold cranking amp (CCA) value may need to be entered in to the tester before testing. Since these are not starting batteries, I don't think Concorde publishes a CCA rating. A good way to come up with a value to enter is to see if Concord does publish a CCA/MCCA rating for one of their somewhat similar batteries sold to the marine or heavy equipment industry. Or look at CCA/MCCA ratings for other 12V Group 4D batteries. If the tester used is designed for passenger car and light truck staring batteries you may just end up using the highest CCA setting of the tester. It is NOT critical the CCA value used is exactly correct for the battery being tested here, just that it is in the general ballpark. For these Concorde batteries this may be approximately 850CCA-1250CCA. What is critical to the testing is that the same CCA value be used for testing each of the batteries. If this testing is performed carefully it may allow the technician to identify one or more batteries which stand out as having a higher internal resistance than the rest of the batteries in the system. Ideally this same testing would be performed when the batteries are new, first placed in service. This would provide a benchmark to compare them to on preventative maintenance service visits and troubleshooting etc. In the case of this existing battery system it would be great if the test could be performed on a new Concorde of the same model for comparison (if available). After individual internal resistance testing I would probably give each 12V battery an equalization charge based on Concorde's specifications. Then I would let them rest, disconnected, for 24 hours and then perform the testing again. If a battery charger capable of charging each battery individually was not available I would consider pairing batteries with the most similar test results into series strings and charging the strings separately, one at a time. And then disconnect them, let them rest for 24 hours, and retest. A couple other pieces of advice with these Concorde AGM batteries: Care must be taken not to charge or equalize them at voltages higher than specified in the manufacturer's literature. Also, care needs to be taken when attaching/detaching battery cables. Over torquing or leveraging the hardware connecting cables to battery terminals/posts can torque the battery terminals/posts and disrupt the seal between the terminal/post and the case among other potential issues. If this occurs the battery may be capable of offgassing around the terminal which will likely cause sulfation on the connection over time. I'm assuming these batteries are configured as a 48V system (2 strings of 4 batteries each). If you end up with at least 4 good batteries perhaps you may consider rewiring the best 4 as a single series string; so the system owner has some backup capacity while they consider total battery system replacement. I hope these thoughts may be helpful. Best regards, ----MATT Matthew Sirum P.O. Box 1227 Greenfield, MA 01302-1227 USA phone: +1.413.773.0611 email: matthewsi...@gmail.com Date: Thu, 1 Sep 2016 12:51:46 +0000 From: Gary Bassett <g...@hudsonsolar.com> To: "RE-wrenches (re-wrenches@lists.re-wrenches.org)" <re-wrenches@lists.re-wrenches.org> Subject: [RE-wrenches] Test procedure for Concorde batteries Message-ID: <4c9022358cd54ad38ff888fd1101fad5@Hosted-MS-3.elcomp.local> Content-Type: text/plain; charset="us-ascii" We have a grid tied battery backup system that uses 8 Sun Xtender PVX-2120L batteries, about 9 years old. The grid has been going out frequently - about 4 times in the past 3 weeks. When the grid goes out, the battery voltage gets too low and shuts the system down pretty quickly. One of the times, this happened within 4 hours. We want to test the capacity of the batteries and we have a testing procedure from Concorde that seems like it would take a lot of time. Is there a quick way to test the battery capacity? Gary Date: Thu, 1 Sep 2016 09:31:58 -0400 From: John Blittersdorf <john.blittersd...@gmail.com> To: RE-wrenches <re-wrenches@lists.re-wrenches.org> Subject: Re: [RE-wrenches] Test procedure for Concorde batteries Gary, I have just two methods I use to test all batteries. I do a voltage check of each battery under load with solar input shut off. You will quickly find a battery with a bad cell or two. It is best to do this test when the batteries are already somewhat discharged to see clearer results. When under charge, and even floating or with a light load, a battery with bad cells can look OK in the voltage check. Bad cells can show up as down about 1.5 to 2 volts for each bad cell from normal. I have also seen batteries that not only dropped in voltage but actually changed polarity. Had a 6volt L16 read -2 VDC. Thatdropped the string by 8 volts!!! Typically bad cell problems will show up after some discharge and if a single string, the string voltage suddenly drops down. In parallel strings the numbers get really random but other batteries in same string will rise high to compensate for the low battery. I have seen a 6 volt go to +9 volts and was boiling violently. (hence why multiple strings are not the best design). If the above checks are OK, batteries still appearing to be weak have reached the twilight of their lives and a plan is needed to retire them. $$$$ 9 years seems about right from my experience to see serious decline in output. The other quick test for parallel string batteries is to use the DC clamp meter to check each string as being roughly equal in current under load or under full charge rate. This will find bad cells, different aged batteries, and /or bad connections. When you lose a string, that will definitely reduce the coasting time. I don't check specific gravity for two reasons. It is time consuming and moving acid around is not good in my book. I have found individual batteries with low specific gravity readings that went on to work OK for many years, If the batteries pass my voltage and current checks, I call them good to go. John Blittersdorf Solar Guru Rob Stubbins Solar (division of Rob Stubbins Electrical and General Contractors) 280 Quality Lane Rutland, VT 05701 802-775-1484 ext 512 Date: Thu, 1 Sep 2016 09:43:53 -0400 From: Tump <t...@swnl.net> To: RE-wrenches <re-wrenches@lists.re-wrenches.org> Subject: Re: [RE-wrenches] Test procedure for Concorde batteries Gary I would suggest that the battery manufacture?s recommended method is followed. Yeah it IS time consuming BUT? Checking w/ a clamp on during a charge or discharge depending on the # of strings &/or the way the strings are configured will be misleading. Your customer is paying by the hour and a the choice is theirs replace OR pay your tech to watch the voltage/current over the manu?s discharge time. These batteries can be run thru an equalization cycle, following the guide lines recommended by Concord, then do your load test. Full charge to discharge over time IS the only way. _______________________________________________ List sponsored by Redwood Alliance List Address: RE-wrenches@lists.re-wrenches.org Change listserver email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out or update participant bios: www.members.re-wrenches.org