If your discharge rate is 1C, then 1 minute is only 1/60th of the charge, so that will be 50 mV (if the 3 V is correct), and you will need to measure the 50 mV change quite accurately, to better than 10 mV. Voltmeters that can measure to 1 mV on a 12 V system are quite expensive.
If they are not dried out and have not been abused, an electronic "desulfator" may restore some capacity.
The concept is that it electrolyses lead sulphate (which forms on the plates over time) back to lead, with the sulphur being returned to the acid.
I've had mixed success trying one on old UPS batteries that have been on permanent float charge; some recover well, others are unaffected.
There are dozens of types on ebay & they are also quite simple to build from either a kit or just buy the components.
desulfator for sale | eBay
Find great deals on eBay for desulfator. Shop with confidence.www.ebay.co.uk
Also on amazon etc.
ps. Pulling high current from a badly sulphated battery may damage it, as only the "clean" area of the plates are highly reactive so the current per plate area is far higher than it should be and that can overheat or warp them.
The voltage waveforms you recorded also appear to be very low voltage, if the scope display is accurate - 50mV per division?
can't be without kitsNeed to quickly estimate capacity of SLA batteries without doing full cycle and without spending hundreds on equipment.
Looking at the discharge curve, fully charged is about 2.25V/cell and fully discharged 1.75V and the curve is fairly linear. In theory, for 6-cell 12V battery, the voltage range between 0% and 100% DOD is approx 3V - 10.5~13.5V. If battery is within this range to begin with, and relatively large load is connected, measure current, voltage, then after 1min voltage drop, approximate capacity in Ah should be I * 3V / (deltaV*60)
Right ?
zip the Excel spreadsheet file and post it.
Regards, Dana.
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