No bubbles whilst charging

[Andrew Eckhardt]

A good lead acid battery that is completely discharged wont gas much at a few amps unil it becomes charged, and they're only about 75% efficient, so don't expect more energy out than you put in. It will take several hours to charge a complety dead car starting battery with a few amps. Even in a good battery the cell resistance will rise quite a bit until it starts to take a charge, so it's normal for the current to slowly rise and then fall toward full charge. If you've had the battery on the charger overnight and the terminal voltage still drops severely under starting load you almost certainly have a bad cell. It would be shame on the battery to have this happen in only 2 years, but sometime the plates will crumble away and leave a high impedance cell even if it is full of electrolyte. Most likely the battery will take a charge and leave you looking for the problem elsewhere.

[Fuzzymuff]

A headlamp isn't a reliable test for a battery. I agree, not a proper load test is it?


Hi sir, I have got it started. The charger I borrowed did the trick. Its funny, I would have thought the old raw full wave supply I knocked up would have done the job???

Hope I don't need a new battery just yet. Anyway, thanks Perry Babin and others. I'm greatfull for your help.

Fuzzymuff

[star882]

One trick I used was to connect a light dimmer, capacitor (1uF or less for a UPS battery, about 5uF for a car battery, use about half the capacitance for 240v), and high current bridge rectifier to make a desulfator. The dimmer and capacitor put out current pulses which help remove sulfation. I have used that on 2 car batteries so far and it works great. It does not work as effectively for UPS batteries.

Maybe a simple circuit can be built to charge a 5uF capacitor from the mains and periodically discharge it into an unused car battery in order to prevent sulfation.