My clock is losing like a minute a day and our old friend Google leads me to believe it could be the battery. Can anybody confirm this please. If so, the battery could well be the original battery and would be 8 years old. The writing on it says: 12V 80AH 800A (EN) 140 RC 800 CCA (SAE) I can see plenty of 80 AH - 720 CCA but not many 80 AH - 800 CCA which seem to be much more expensive. Do I have to replace like for like?
Your replacement will require registering with the car - if you change capacity [e.g. to a larger one] it needs coding to the car so the electronics adjust the charging rate(s) accordingly. Some have replaced identical ones without problem, but registering is recommended. At 8 years old it doesn't owe you anything, these cars are complex and 'hard' on the power source.
Can you not? Remove the intelligent charging lead and remove the requirement to code the Battery ??? Is is this frowned upon ......
Mmm! don't know for sure but knowing BMW and sods law something else in the system will not like it so might be a gamble. Here is an article on the subject which is worth a read and then the decision is yours as they say. http://www.motor.com/article.asp?article_ID=1479 Regards Mak
As Slim says if the capacity is the same then it only requires registering. I would think removing the IBS lead would introduce other errors into the system, a permanent fault code for starters. The new battery won't last very long. It's not particularly hard to code for a different battery size, even easier to register a battery change.
But can be cheaper if you know where to look ;) I got a Varta for about £155 inc delivery and I've seen them for sale for over £200 on various sites.
Is the battery casing black? If so it is an AGM battery so will ideally need to be replaced like for like and as others have said registered. If you want to know the age of the current battery it will be stamped into the top of the negative (i think) battery post showing week and year of production.
Usually losing time or the time resetting is the symptom of a duff cell in the battery. What happens is when the car starts the battery dips really low (like say 7V) and this causes the loss of time. This tends to persist for a while until the cell lets go completely and the car won't start at all.
You need to replace AGM with AGM or lead-acid with lead-acid (unless you get the car coded for the change). If you have stop-start technology it's likely to be AGM. If you don't it's likely to be lead-acid. But that's from the factory the previous owner may have changed the battery. There's a difference between "coding" and "registering". Coding is entering the battery details e.g. is it lead-acid or AGM and is it 100Ah or 90Ah. The battery type changes the charging voltage - so ensuring this is correct is the critical thing. The battery capacity (Ah) is used in calculations for how much charge is left in the battery. "Registering" a battery is essentially resetting all the stored usage logs - so the car doesn't think the battery is flat when you've just put a fully charged new one in. If you fit the same type battery (so coding isn't required) but you don't register it the car will eventually figure out the state of charge (I think it'll take around 7 days) but it's not ideal and you might initially get the odd "Battery Low" message when it isn't really. If you fit a slightly greater CCA battery that won't affect anything. If you fit a slightly greater Ah (say 5Ah or 10Ah) battery you'll not have an issue. The battery will still get a full charge but what will happen is the car may consider the battery flat when it still has the extra 5Ah or 10Ah in it (and the car will start when it doesn't think it can). The battery Ah is only really a guide anyway; it diminishes with age and the true value has a tolerance on it too.
Apologies for the delay in getting back with the update, and thanks for all of your replies. The battery was duff and was down to 35% of its life left. It was not an AGM battery (and the first thing they asked me at the motor factors was "is it a stop/start" - it isn't), so I replaced it with a Varta 80 Ah 720CCA (the old one was 800CCA). Cost around £85 but slightly smaller in height to the original factory battery it replaced, so I packed it out with a block of wood so that the clamp bracket fastens down on top of the battery case to hold it fast. Although the only visible thing that needed re-setting was the clock, I took it to my BMW specialist indie who registered it to the car for £20. Took him all of 10/15 mins. Everything seems to be fine now.
