Starting the 8 after being parked for a week

Going back a few steps what is everyone recommended battery power. I know what the manual says. Also GSF part suppliers suggest 66AH @ £60 + VAT each. My question is this. With a 850 to start is there an advantage of buying bigger (Ah that is) .
I only ask this because I want to treat the car to a new pair of batteries.

850 parked for a week

Hi
I have my 850 for about 10 years. I very rearly drive the car. I keep it just for the looks, so most of the time it sit up for 6-8 months. I just have a battery charger and charge the batter every month or couple of months. I have absolutely no problem with mine starting right up.

No ticking at all?

Is it v12 or v8?

Just been in Halfords and they also sell Calcium battery. Does any one have any experience of these. They cost a little more but are guarented for 4 years. Listed as suitable for cars with lots of gadgets etc.
This is to go on a V12. I want to sort this this weekend so if you can please advise me ASAP. I will of course buy a pair.

Dare I add to this long expired thread......

My batteries died a few weeks ago. Car has had little use for the last 6 months and they were 3 years old. Saying that they were quality 75AH 096 type. I replaced again with 75AH 096. The specified 65AH seems a bit lightweight in my inexpert opinion.

I was interested to note that the owners manual (pp 105) recommends disconnecting the negative terminals for periods of inactivity exceeding 4 weeks.

As the winter approaches a lot of 8er's put their cars into hibernation over the cold months. My car is in forced early hibernation mode due to a failed propshaft centre bearing and I will be doing a pre-winter check later this weekend.
Over on clube31.de (german site - I note that the dot de gets automatically resolved into dot net)there have been a few threads on the topic of disconect the batteries or not - the general consensus of opinion is that you should not disconnect unless you have to, it's better to have a trickle charger (such as a cetek) running or charge the batteries every so often during the hibernation period. The reasons for not disconnecting were firstly you have to reset a load of stuff on re-connect (actually very easy to do anyway) but more importantly a warning story about capacitors in the instrument panel that don't like a sudden re-charge. The problem seems to be that as the capacitors get older they become less able to deal with sudden voltage loads and they can fail - this results in all the instruments going "dead" and the needles not moving. I'm not speaking from personal experience here but this phenomena was reported on club31.de and linked to BMW 7's too.
If this is cobblers then I'm sure 8tech will be along in a minute to slap my wrist

I intend not to disconnect but I have brand new batteries (BMW OEM - they were actually cheaper than no-name aftermarkets) and I have access to a power point in the garage and can put the batteries on charge from time to time.

(I'm also hoping for a mild winter)
Cheers,
Jason

hi all
just gone back to my blue 8 after 3 weeks of sitting.
started first time.
the batteries havent been changed by me and ive had the car for 2 years.
it was sitting for 14 months before purchase and the previous owner didnt change them either.
they are good quality high current batteries so thats the route to go.
also my black 8 sat for a month with no start and that started first time aswell, again high current quality batteries.

I usually have my car parked for 4,5 weeks at a time when I'm at work.
This has not given me any el-power problems in the past, but when I installed a tracker system in the car the car was stone cold dead after 4,5 week.
Guess the tracker needs some power.
I've been thinking about getting new high power batteries next year.

As for the ticking noise.
I guess the V12, like most BMW engines, also have hydraulic valve lifters (not sure its called this in English).
If there is not enough oil pressure, or there is air in the lifter, the engine will tick like hell.
I've done some track driving with BMW's 6-cylinder cars and they sound horrible after a couple of laps.
But when you drive it home it sounds perfect again after a few minutes.
This is due to air bubbles forming in the oil when it is thrown around in the oil sump, and air goes to the highest point, the head, and get stuck in the lifters, the lifters don't operate perfect anymore, and the valve starts ticking as it hits the head when it's closing.
This is not dangerous at all.
Same thing when starting her up after a while, all the oil has been drained to the sump, and it takes a few seconds to get the pressurr up and the air out of the heads.

So Hemibum, what you experienced was probably just an air bubble in one of the valve lifters.

Hydraulic lifters also wear and start to leak oil when the engine is not run. This is why there is a noise just after starting which goes away when the oil pump has time to supply some oil (back) to the lifter and make the correct adjustment to the tolerances...

It's not the pressure it is about the amount of oil in the lifters which makes the adjustment to be out of whack.

OK Guys, thanks for that. Actually, this happened only the one time.

Since my original post I've never had the problem again.