Recovering bad sealed lead acid batteries

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9 years 3 months ago #1101 by Juzzie
That's a brilliant result, Dan. I've lived with stand alone solar power for years and never considered it possible to top up a gel cell. I'll be keeping your experiment in mind....

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9 years 3 months ago - 9 years 3 months ago #1102 by mw0uzo
Prior to this I probably would have said it wasn't possible, only in lucky cases. Well, let's see if it holds a charge. It was charging at 450mA on a normal 13.8v supply about 2hrs ago. About to check on it.

... current had crept up to 490mA and battery was warm. Reconnected to power supply with better controls and set at 100mA charge with voltage limit overnight. That should give 1Ah of charge and we'll see if it will take any more tomorrow. A quick increase of the voltage saw a lot of current draw, so the internal resistance must have gone down a lot.
Last edit: 9 years 3 months ago by mw0uzo.

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9 years 3 months ago #1104 by Juzzie
Beware, heat is not a good sign. Ensure the space is well ventilated, or at least periodically well ventilated.....

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9 years 3 months ago #1105 by mw0uzo
ok after 11hrs of 100mA, the battery was cool and had a voltage of about 10.8V, so still quite discharged.
Connected to normal 13.8V supply, charge current is 420mA, 13.5V.
I wonder if it will fall or just stay like that.. the current should surely fall soon if the battery is ok. At least its less than 490mA last night.

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9 years 3 months ago #1106 by mw0uzo
Back up to 500mA now, if its not started to fall by 8hrs then there's something wrong.

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9 years 3 months ago #1107 by mw0uzo
3hrs later. Up to 600mA. Warmish. Disconnected measured off load voltage, 10.6V. I would have thought it should be higher than that by now.
Switched to variable PSU and charging at 800mA, 14.4V.

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