What % charge should my battery typically be? 2011 30is

Dannheisser · Post by **Dannheisser** » Sun Mar 24, 2024 11:34 pm

ronk · Post by **ronk** » Mon Mar 25, 2024 12:06 am

On a maintenance charge - 13.6v

Dannheisser · Post by **Dannheisser** » Mon Mar 25, 2024 12:42 am

Bimmerlink says I'm 35% of charge...voltage over 14

flybobbie · Post by **flybobbie** » Mon Mar 25, 2024 1:07 am

My battery history showed 85 for a few weeks then dropped to about 60 odd. So long as car starts and i see 14.7 volt charge i don't worry.

fatbaldboy · Post by **fatbaldboy** » Mon Mar 25, 2024 6:42 am

I had a similar number show via bimmerlink - so I left the battery on smart/maintenance charge overnight with my noco genius thing and the next day...no different.

I'd had and continue to have no actual issues at all so I'm ignoring the low charge number

deltasierra · Post by **deltasierra** » Mon Mar 25, 2024 8:54 am

A fully charged battery should read 12.8v resting and should not drop significantly for several weeks after charging and around 14.5v charging with alternator.
When a battery reaches the end of its life resting voltage will drop AND when you start the engine voltage will drop below 12v which will cause car electronics to malfunction, multiple electronic faults is a sure sign of a failing battery.
Battery life varies a lot, maybe 4 yrs is typical, some go on to last 10yrs, some fail early, if you are using a trickle charger make sure it only tops up the battery when voltage drops, do not leave a battery on continuous charge however small.

flybobbie · Post by **flybobbie** » Mon Mar 25, 2024 9:07 am

I think when you code the battery it sets the "clock" to 100%. (Does it need a fully charge battery when fitted?).
Then just monitors battery voltage and guesses it % rate.
Then adjusts charge with time to extend battery life.
I think having an agm battery is more reason to last longer.

Have here agm motorcycle battery. Normal battery if not cared for died every year not being used, sulphated.
The battery i have now is 3 years old and only took 10 minutes of charge even though bike not run for 4-5 months.
Sat all winter and bike just started before i charged it.
If you have bike i can recommend get agm type. I have Motorbatt brand.

deltasierra · Post by **deltasierra** » Mon Mar 25, 2024 1:38 pm

AGMs are a lot more expensive and often used on cars with Stop/Start engines, they are just as prone to failure, standard FLA batteries are fine for normal use. If you lay the car up take the battery off and charge it a couple of times during winter.

B21 · Post by **B21** » Mon Mar 25, 2024 2:47 pm

The charge should be between 60% min and 85% max..

It’s never more than 85% normally as the reserve is gone use when regenerative braking is used.

You see that it if you charge it to 100% then drive it..it will always take a charge as it will not charge the battery till it’s 85% or lower..

Irrespective of use of stop/start it needs to be an AGM on E89 due to regenerative braking.

ronk · Post by **ronk** » Mon Mar 25, 2024 3:52 pm

How are folk measuring %ge charge state if the battery?

Pondrew · Post by **Pondrew** » Mon Mar 25, 2024 4:26 pm

ronk wrote: ↑Mon Mar 25, 2024 3:52 pm How are folk measuring %ge charge state if the battery?

Many code readers read the data from that 'logged' in the car.
Don't think it is particularly relevant on a daily basis, as all mine have been read and none are usually more than 70% ish on the data, bearing in mind they are all trickle charged very regularly and all hold voltage well.

mcbutler · Post by **mcbutler** » Mon Mar 25, 2024 7:53 pm

Dannheisser wrote: ↑Sun Mar 24, 2024 11:34 pm What % charge should my battery typically be? 2011 30is

SO long as it doesn't drop below 11.9V it'll be fine, discharge below 11.9 can permanently damage lead acid batteries

deltasierra · Post by **deltasierra** » Mon Mar 25, 2024 8:29 pm

B21 wrote: ↑Mon Mar 25, 2024 2:47 pm The charge should be between 60% min and 85% max..

It’s never more than 85% normally as the reserve is gone use when regenerative braking is used.

You see that it if you charge it to 100% then drive it..it will always take a charge as it will not charge the battery till it’s 85% or lower..

Irrespective of use of stop/start it needs to be an AGM on E89 due to regenerative braking.

I havn’t come across regenerative braking on an E89 please explain how it works

flybobbie · Post by **flybobbie** » Mon Mar 25, 2024 8:47 pm

Alternator loads engine, so when accelerating or cruising off load. If decelerating alternator kicks in. (I assume depends on battery charge state).
But it must somehow manage current because voltmeter i have fitted, voltage never changes, only on start, it takes a few seconds to kick in.

I even have the "Efficient Dynamics" sticker BMW supplied, but never fitted.

B21 · Post by **B21** » Mon Mar 25, 2024 10:16 pm

flybobbie is correct…DME decouples alternator under acceleration..when you touch the brakes then alternator kicks in adding 4-5 BHP worth of de acceleration..

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