[ROBM2C]

I have seen a lot of complaints about the battery discharge warning if you don't drive the car enough .

I haven't driven the car for 10 days . Today it started up fine but I got the "discharge" warning .

I went for a 120km drive on the highway got back after driving it for an hour and after I turned off the car ...I still got the battery "discharge " ..

Yes go to the dealer I know but anybody having the discharge warning after driving for over an hour ?

Is this just the nature of the car ?

I miss old cars let me tell you ...my old Acura TL could sit in -30 for a month and never have a battery issue .

[ROBM2C]

After talking to a dealer they said bmws are notorious for this , especially in colder weather and the car must be driven 45mins to an hour at least twice a week to keep the battery happy .


Love this car , but that's my only gripe about it !

[fullstack]

The battery doesn't charge all the time just because the wheels are turning. There is an indicator that let's you know when it is charging. It only charges when there is no gas input so on the highway, unless you're going downhill for a stretch you tend to be constantly on the gas to maintain speed.

[ROBM2C]

Ok I will pay attention to this ...so you technically will get a better charge letting it idle then on the gas driving ...interesting .

[AlpsRider]

If you don't drive your car for 10 days, especially in cold months, it's best to get a trickle charger. Letting the battery drain like that will decrease the life of the battery.

[ROBM2C]

This would be the first car that I would need to charge for not driving it for 10 days .

Granted I never had a car that used up so much juice on accessories .

Am I confused or do most other cars constantly charge the battery from the alternator the whole time the car is running ?

I mean weather I used the gas peddle or not the car was on for over an hour .

I'm going out again tomorrow , if I get the same warning after driving all day she's going in for a new battery or alternator check.

[fullstack]

Originally Posted by ROBM2C

Ok I will pay attention to this ...so you technically will get a better charge letting it idle then on the gas driving ...interesting .

Not idle. Hitting the brake initiates the charger. You nee to tap the brake and let it cruise without hitting the gas and the blue gauge lights up which means it's charging. Hitting the gas turns the blue gauge red and moves to the right which means it's not charging. They did this for performance.

[AlpsRider]

There must be some kind of override so that a very low battery will still charge even if it burns more gas.

[NISFAN]

Originally Posted by fullstack

Not idle. Hitting the brake initiates the charger. You nee to tap the brake and let it cruise without hitting the gas and the blue gauge lights up which means it's charging. Hitting the gas turns the blue gauge red and moves to the right which means it's not charging. They did this for performance.

You are talking about 'regen' charging. This is when the battery is supercharged during coasting (blue eco bar present). That is not the only time the battery charges, it charges constantly when driving depending on battery level. The system will prioritise charging a low battery. You will notice this by seat heaters not delivering full power, auto stop start being disabled, even cabin HVAC not heating as it could.

The reason modern BMW's are more sensitive to being left for weeks without use is because for eco reasons, the battery is considered 'full' at 80%. This is to allow capacity for the supercharging regen events, and the fact that the last 20% takes significantly more energy to add charge.

The advice to use a trickle charger is sound for the infrequent user.

[Kankles]

Optimate. Namaste

[fullstack]

Originally Posted by NISFAN

You are talking about 'regen' charging. This is when the battery is supercharged during coasting (blue eco bar present). That is not the only time the battery charges, it charges constantly when driving depending on battery level. The system will prioritise charging a low battery. You will notice this by seat heaters not delivering full power, auto stop start being disabled, even cabin HVAC not heating as it could.

The reason modern BMW's are more sensitive to being left for weeks without use is because for eco reasons, the battery is considered 'full' at 80%. This is to allow capacity for the supercharging regen events, and the fact that the last 20% takes significantly more energy to add charge.

The advice to use a trickle charger is sound for the infrequent user.

Thanks for the info. I'm talking about the "efficient dynamics" charging. And it is on all the time. I read that the car doesn't charge unless the battery symbol at the end of the blue bar is lit and that the alternator is decoupled so the engine doesn't have to work as hard to run it during that same time saving fuel and increasing performance.

[NISFAN]

Originally Posted by fullstack

Thanks for the info. I'm talking about the "efficient dynamics" charging. And it is on all the time. I read that the car doesn't charge unless the battery symbol at the end of the blue bar is lit and that the alternator is decoupled so the engine doesn't have to work as hard to run it during that same time saving fuel and increasing performance.

No that is incorrect. The blue bar shows a type of 'super charging mode' like a regen if you will, however the battery still charges during normal driving too (even when the blue bar isn't showing).

But yes it also has an intelligent battery charging system which can cut charge rate under hard acceleration. As well as reducing ancillary drain when battery levels are low.

[///MCollection]

The alternator charges all the time as far as I'm aware the efficient dynamics is on top of that. If you put a volt meter on your front posts and check battery voltage it should be 12.4 to 12.6 on a good battery and starting it up should push that to 13.5 to 14.5 volts

[Higgs Boson]

Originally Posted by ///MCollection

The alternator charges all the time as far as I'm aware the efficient dynamics is on top of that. If you put a volt meter on your front posts and check battery voltage it should be 12.4 to 12.6 on a good battery and starting it up should push that to 13.5 to 14.5 volts

Most modern cars have variable output alternators, oil pumps, fuel pumps, etc and can increase or decrease output depending on circumstances.

[doughboy]

Originally Posted by ROBM2C

After talking to a dealer they said bmws are notorious for this , especially in colder weather and the car must be driven 45mins to an hour at least twice a week to keep the battery happy .


Love this car , but that's my only gripe about it !

Eh.? Wtf? Never heard or experienced this. Do BMW use inferior batteries or alternators? NO.

45 mins twice a week??? He is mad.!

I often leave my M2C unused, outdoors, for weeks at a time in winter, never missed a beat on startup same as previous M6 and 335i, 330i etc.

Faulty battery is not an uncommon issue...

[ROBM2C]

@doughboy exactly I never had a car that wouldn't start after 2 weeks so I'm going to monitor it and see how much the voltage drops after a couple days and might bite the bullet and bring it in .

[Artemis]

Originally Posted by ROBM2C

After talking to a dealer they said bmws are notorious for this , especially in colder weather and the car must be driven 45mins to an hour at least twice a week to keep the battery happy .
Love this car , but that's my only gripe about it !

Late February I left one of my cars at an airport somewhere in Europe. Lockdown happened in March 2020, borders closed and so the car got stranded. Picked it up again in July: turned the key and the engine fired up straightaway. No probs. First sprayed the frontscreen to clean all the dust. No BMW.

During the lockdown I drove my M2C at least once every 6 weeks for an hour or so to ensure recharging the battery.

[Killed by Death]

Take it to the dealer. My wife's X3 had a defective battery and was replaced under warranty after almost 4 years of use.

[PackPride85]

Buy a cheap battery charger from Amazon and hook it once a week.

[ROBM2C]

So I threw a multimeter on the battery yesterday after a drive and it read 12.41v.
Today less then 24 hours later the battery reads 12.08 volts 🤔


I have a scheduled service in 6 weeks , we will see what the dealer does . I will keep it posted .

[AlpsRider]

Originally Posted by PackPride85

Buy a cheap battery charger from Amazon and hook it once a week.

This∆
Even if the battery has enough charge to start the car, repeated draining of the battery will substantially decrease it's lifespan. A LifePo4 battery would be a different story, but we're talking about a lead acid battery.

[Fined]

I'm not using my car at all almost all year this year. Only starting in December did I start seeing the battery discharge message. The only place the car goes is to the grocery store once every 10 days, and the grocery store is only 2km away.

So now I've started to have some drives. About one hour of driving then go to the grocery store. Now I do not get the message any more.