Is a 540amp battery sufficient

[Russ35]

Is a 540amp battery sufficient, as mine has died and a have a spare 540amp battery in the garage. Currently have a (dead) 640amp on the s3.

[tvrgit]

Russ35 said:

Is a 540amp battery sufficient, as mine has died and a have a spare 540amp battery in the garage. Currently have a (dead) 640amp on the s3.

If you're using it a lot, so that it doesn't have time to discharge to any great extent while sitting in limbo, then a 540 amp-hour should be ok.

A more important factor is the peak starter cranking amperage - a smaller battery might not have (or keep) enough "ooomph" to turn a big engine over at starting speed on a cold morning.

Once the car has started, it should run (more or less) on the current the alternator supplies, (unless you run it everywhere on short journeys with the lights and wipers etc on so that battery doesn't get a chance to recuperate) so its overall amp-hour capacity is less important

[Barkychoc]

The starting capacity may be marked on the battery as CCA (cold cranking amps).

Chris

[Road2Ruin]

Yes the important bit is the Cold Cranking Amps. It has to be quite high for this type of vehicle. I had a smiliar 540 amp battery and thought it might do but after about a week. got the fatal click, click, click, click of the starter indicating not enough oomph. Put a fresh 620 in and noe no problems at all.

Peter