Jonathan,
just think of it as a larger 'reservoir' of stored energy, which would take longer to be depleted if your car was struggling to start on a freezing cold morning.
The alternator might take slightly longer to 'refill' the larger capacity battery if it was almost discharged, compared to a lower capacity battery, but any alternator will take that in its stride.

Most useful for those folk with high-draw sound systems in their motor, I'd have thought...

ken

Russell, when I measured my current battery, the flange at the top is similar in size to that at the bott. Anyways, fait accompli...

Jonathan, a few extra Ahs ain't the be-all, but can be useful. CCAs (how much cranking amperage it can provide) are different but generally connected. More of each will just you more 'reserve' power when it's needed. A run-down larger capacity battery will take longer to charge up again, but the alternator will do it no problem. In general day-to-day running with a car that starts without difficulty, you wouldn't notice any difference between these batteries. When the day comes that the leccies are a bit damp and the car a bit stubborn, then it could make all the difference.

Dammit, Ken said it sooo much better...

Wot, this bit?

"Most useful for those folk with high-draw sound systems in their motor, I'd have thought... "

You need my batter. 770 CCA. Spins it over well

Ps I disconnected citroen a measly battery cables and went for a set of Marine cabled lorry sized cables. Can't remember what size exactly but I think about the 10mm mark. Being marine corrosion and dodgy connections won't be a problem

Woooooo, this thread is gonna run and run...

I'm sure your cables are wonderful, James, and should reduce the likelihood of any terminal/corrosion problems in the future.

Just for interest's sakes, fitting oversized cables won't have any direct effect (improvement) on the starting performance provided by your huge battery since the amount of current drawn by your starter motor will be exactly the same as it was before - if it drew 250 Amps whilst cranking on your old battery and cables, it'll still be drawing the same today. Only now it'll continue to draw it until the wee sma' 'oors, but that's the only difference. (Some pedant will point out that the fractionally lower resistance of the thicker cable will provide a teeny, but generally unmeasurable improvement... )

Hey ho.

Anyways, I'll report back when t'new battery turns up - and if it fits.

but do they guard against terminal operator error?

One is red and one is black

Starter spins faster in the cold !!