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MG MGA - How long should it take to charge a battery?

Wanted to go for a spin today. After three or four turns of the key the battery was flat (or appeared so) and so I put it on charge. After 15 minutes the car started as if the battery was new. Surely it should take longer to charge the battery, and I wonder what else it might be.
Any ideas?
Nigel Munford

This is normal. A lead-acid battery will maintain most of it's normal operating voltage down to about 80% discharge (20% charge level). At lower charge lever voltage drops off rapidly. Discharged enough to prevent cranking is more like 10% (or less) charge level. Recharging it from 10% t0 20% charge level needs only 4-AH of power input. A 10-amp charger will do that in 20 minutes.

However, just because it cranks well enough to start does not mean it is fully charged. There is also the question of why it was discharged in the first place. When it is running check function of the generator to assure it work properly. If not, then fix it. Then check function of the control box to assure proper charging voltage at all engine speeds. If not, then adjust it or replace it as required. Always verify function of the generator before fiddling with the control box. Information for testing and adjusting generator and control box is in the Workshop Manual.
Barney Gaylord

Check your battery connections for any corrosion or loose fittings first; it may be as simple as that, or the battery may be the issue (how old is it?). I had similar symptoms (not on my A) and turned out that one of the battery cells was completely dead, even though the battery was only 1yr. old; sometimes age is not the only factor. The battery would take a charge, I could start the car and drive it, but if it sat for a day or so, it would completely discharge. Hope this helps.
Nick Kopernik

Thanks for your answers and advice. More investigation required.
Nigel Munford

Also suggest making sure that the battery top surface is clean so that there is no path for discharge.
Ira Spector

This thread was discussed between 24/08/2014 and 01/09/2014

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