Do new lead acid batteries need a discharge before they operate properly? - Page 1
Forum section: electronics / projects

author: AndersJ
author_rank: Frequent Contributor
timestamp: January 13, 2019, 06:44:32 am
content: My product uses two serially connected 12V 7,2 Ah lead acid batteries for battery backup.I have a requirement that a bad battery must be detected within 4 hours.Therefor a load test is done every few hours to test them for full capacity.This has been working well for 5-6 years.Now I am seeing false battery test warnings in some new systems,and/or systems where batteries have been replaced recently.One of my service engineers, that also does some of the system installations,mentioned that ”his” installations never have this problem, but others do.He also mentioned that on first time installations and after battery replacement,he turns off mains power to run the system on the backup batteriesfor about an hour to ”get them started” or ”excercised”.After that mains power is turned back on for normal mains powered operation,starting with a full charge.Does anyone have similar experiences?Do new lead acid batteries need a discharge/charge cycle before normal operation?

author: floobydust
author_rank: Super Contributor
timestamp: January 13, 2019, 07:29:35 am
content: Are the false battery test warnings just at startup or do they occur continually now?A new battery pack gets charged for hours before the test starts up- long enough to overcome storage losses and do equalization?Did you change battery type or manufacturer? The chemistry may be different, between UPS high-discharge, deep cycle etc. and your fail criterion (voltage) may need an update.Otherwise, it sounds like a passivation layer but I can't find anything saying a discharge is required to remove it, like in Li-SOCI2 lithium (primary) batteries.This paper saying charging removes the layer and possibly a dependancy on how the battery was factory charged:Self-Discharge and Passivation Phenomena in Lead-Acid Batteries during Storage pdf

author: AndersJ
author_rank: Frequent Contributor
timestamp: January 13, 2019, 08:00:48 am
content: False battery tests occur continously, within a few days to a couple of weeks.A new battery pack creates battery test warnings while charging to full capacity.After that warnings cease, but come back now and then, andthatis the problem.I can live with warnings during initial charging, in that scenario warnings are expected.No battery type change.

author: spec
author_rank: Frequent Contributor
timestamp: January 13, 2019, 08:59:06 am
content: Over the years I have found lead acid batteries to be rather odd. In one case, a 12V 33AH battery was used to power an equipment that only consumed an amp at the most and the battery was never discharged to less than 60% capacity. Also it was only left in this discharged state for a maximum of four hours.In spite of this benign regime the batteries never lasted more than 6 months (low capacity, high internal resistance). Yet the same type of battery fitted to a car had no problems. So it does seem that some batteries like to be 'excercised'.We were going to get some deep discharge batteries which I understood would survive OK, but in the end we changed to NiCad or NiMH, cant remember which.My advice, for what it is worth, is to look into the lead acid battery options, and if you are not already doing so, evaluate the deep discharge type. Of course, the real answer would probably be to go for LIIon.

author: amyk
author_rank: Super Contributor
timestamp: January 13, 2019, 06:51:51 pm
content: Quote from: spec on January 13, 2019, 08:59:06 amFor a typical automotive lead-acid battery, 60% discharge isextremelydeep. Remember that in a car it's going to be charged fully almost all the time.

author: floobydust
author_rank: Super Contributor
timestamp: January 13, 2019, 07:36:45 pm
content: I think your hypothesis is wrong, it's not the batteries.It's either the act of replacing the batteries that causes a problem or something on the control board ages and generates false battery failure alarms. So an old or new battery would make no difference for alarms chattering.Corrosion/oxidation of the battery connections, or installers that trash the spade connectors can add resistance to the battery connections, so voltage would sag more under load.With age, the control board voltage reference can drift and are your charging and load-test voltages staying accurate after many years? You could be perpetually undercharging or measuring low during the load-test.After 10,000 cycles of load-tests, there better not be a relay involved.Last guess would be a firmware bug in the control board. The version is the same at all the sites?Do you (hot) disconnect and replace the batteries, or do you first power down the system then disconnect the batteries etc. Do you power-up first with batteries or with mains?Point is each tech might do a different sequence and there may be a side effect in the firmware.