What Amp-per-hour Battery?

[Ian Simmonds]

Just swapped the battery, put in a 63ah in, but took out a 74ah... Standard(ish) S2 Avant. Any idea what it should be? VAG dealer seemed to think 74ah was a bit excessive for a petrol car with 1993 electric current draw.

[s2avant]

The biggest battery they ever fitted was 64Ah and that was mostly for diesels. 63Ah is fine on an Avant.

There is not much point having a massive battery unless you have an alternator that can charge it.

Ben

[mcandmar]

Never seen a 74ah, all our cars have the 64ah. Some S2's did get a larger alternator, 120a vs 90a for some reason, i think it was cars with AC and the cold weather pack so its possible they had a higher rated battery.

[porkkis]

I use Varta type D24 which is 70Ah nowadays. It's some uprated model of the old D24 which was 64Ah.

There is absolutely no connection in battery capasity and alternator output. Use as big as possible. 10A alternator can charge any battery, it just takes longer. It's not amp per hour but amp times hour. 70Ah means you can draw 10A for 7 hours if it was full.

I'd like to have a lot bigger as I'm using a petrol operated heater. 100Ah or so, but there isn't just room for one without quite massive job.

The theory with larger alternator option from factory sounds plausible as my car had 90A and is with A/C but no winter package. I've changed the alternator to 120A to compensate the heater.

Battery capasities vary between manufacturers. It's the measurements you should worry about. 175mm wide, 175mm high and 280 something long.

http://www.varta-automotive.com/eng/ -> which battery -> search by vehicle
Too bad it doesn't tell the short number, but I bet the 70A one it offers for A80 B4 Avant S2 is D24 by it's short designation.

[mcandmar]

There is absolutely no connection in battery capasity and alternator output. Use as big as possible. 10A alternator can charge any battery, it just takes longer. It's not amp per hour but amp times hour.

Yes good point