General Cold Start Battery Questions

[Dee_82]

quick question on battery figures, I know this is has been covered by a dozen or so separate posts but I didn't want to hijack anyone else's issues but feel free to use this thread for your own questions.

the other morning my car failed to start, gave it an hour on charge and all was fine, for a while now its been a bit slow in starting, just an additional turn or two, nothing major.

today I decided to check over the figures, key off 12.2v, key on, 14.2 key off current drain, 0.67A

how does those compare with you guys?

on a hunch the battery seems a little low, its a ford battery so probably the original, but it doesn't seem that low. I guess its also possible the battery terminal wasn't perfectly connected as a single hour on charge only gives it 3 amps which shouldn't have been enough.

any thoughts

[IINexusII]

its not just the battery voltage, during cold starts it depends on the CCA of the battery too (cold cranking amps? or something like that)

[Dee_82]

yeah, I don't have a tool for measuring that, I know if I turn an engine over the voltage will drop like a rock then slowly build up to 14 again, im sure I read someone a long time ago there was a limit it should drop too, lower than that indicates its taking the charge but not holding it.... just cant remember or find that minimum voltage level! Grr!

[stef123]

You need to measure the battery voltage under load. Turn the engine over and measure the voltage and see what you get