[CP911]

I was somewhat surprised to find my new 2er's battery took quite a while to charge with the BMW battery charger (OEM CTEK charger). It took 4-5 hours before it moved out of the bulk charging stage and I had to leave it plugged in all evening and overnight for it to fully charge. They say if you take small trips, your alternator never really gets a chance to charge up the battery. Well, my first trip was a 700 mile road trip from SC to IN, so even more of a reason why I was so surprised to find the battery was depleted as much as it was.

Is this normal? Do you all "top off" your batteries occasionally even when not in winter storage just to maximize battery health and service life? I am planning to from now on. I'm thinking once a month or every couple of months would be better than nothing.

Anyways, just wanted to share my findings and remind everyone out there to charge your batteries unless you feel like buying a new $400 battery sooner rather than later.

[Kolyan2k]

I haven't charged a single battery since 1990s

[Elvisfan]

Originally Posted by CP911

I was somewhat surprised to find my new 2er's battery took quite a while to charge with the BMW battery charger (OEM CTEK charger). It took 4-5 hours before it moved out of the bulk charging stage and I had to leave it plugged in all evening and overnight for it to fully charge. They say if you take small trips, your alternator never really gets a chance to charge up the battery. Well, my first trip was a 700 mile road trip from SC to IN, so even more of a reason why I was so surprised to find the battery was depleted as much as it was.

Is this normal? Do you all "top off" your batteries occasionally even when not in winter storage just to maximize battery health and service life? I am planning to from now on. I'm thinking once a month or every couple of months would be better than nothing.

Anyways, just wanted to share my findings and remind everyone out there to charge your batteries unless you feel like buying a new $400 battery sooner rather than later.

There is no logical reason for you to have to top off your battery. I’ve never heard of such a thing. Unless there is something wrong with the battery or the charging system. Where did you get that idea? Bring it in and have it checked.

[CP911]

Originally Posted by Elvisfan

There is no logical reason for you to have to top off your battery. IÂ’ve never heard of such a thing. Unless there is something wrong with the battery or the charging system. Where did you get that idea? Bring it in and have it checked.

Perhaps this can be debated by the scientists and battery engineers, but it is widely known that keeping lead-acid batteries in a low state of charge for extended periods of time or repeated deep cycling (going from charged to discharged) is bad for battery life. There are certain batteries optimized for these conditions, but generally speaking, it's not a good thing for these types of batteries.

If I can avoid prematurely replacing $400 batteries over the lifetime of this car by investing $100 up front on a decent charger, by all means I'll do it. Now, if you trade your car in every 3 years, then I can understand why you probably don't give a crap enough to bother with it. However, for me, this is a special car, so I do not mind taking special measures to keep her in good health.

[inc235]

No. I do a weekend highway run occasionally though. Never had a problem starting even in -10'F that was here a couple weeks back.

[Ron Jeffries]

I suspect a problem in the charging system tho.

[morphomeman]

Whatever floats your boat. OP is not doing anyone any harm, so if this makes him feel better, it's fine with me. That said, I have owned a good number of BMW's over the years, some for a very long time, and never had to change a battery.

[Ron Jeffries]

I kept one for quite a few years once, and replaced its battery. And I think I had a battery not survive winter storage one time. But if it's down, I gotta suspect the charging system (or the charger used).

[ianp622]

Originally Posted by CP911

Perhaps this can be debated by the scientists and battery engineers, but it is widely known that keeping lead-acid batteries in a low state of charge for extended periods of time or repeated deep cycling (going from charged to discharged) is bad for battery life. There are certain batteries optimized for these conditions, but generally speaking, it's not a good thing for these types of batteries.

If I can avoid prematurely replacing $400 batteries over the lifetime of this car by investing $100 up front on a decent charger, by all means I'll do it. Now, if you trade your car in every 3 years, then I can understand why you probably don't give a crap enough to bother with it. However, for me, this is a special car, so I do not mind taking special measures to keep her in good health.

Except the 2-series doesn't use a regular lead-acid battery, it uses an absorbent glass mat battery, which is explicitly designed to handle cycling (better for it not to be too deep, but certainly deeper than a lead acid). This is how you can have a start-stop functionality.

Also, even short trips should be fine, as you have regenerative braking, assuming you don't go from foot on the pedal to screeching halt all the time.

The reason it takes so long to charge is because the battery is so large - you know you need a crane to take it out, right? In fact, I would worry more about damaging it with the charger than it not being at peak capacity all the time. You need to make sure you have a voltage regulated charger or you could be damaging it more by charging it yourself.

Also, if the car thinks the battery level is too low, it will disable start-stop functions. If your car isn't doing that, the battery is where the car wants it to be.

[Cumberlandjames]

There are so many things that impact battery charging, the type of charger, battery condition. age and temperature to list a few. Looking at the CTEK charger I see it uses very small gauge leads. This in indicates that it does not produce much current and therefore will take a longer time to recover a discharged battery. It appears to be more of a "tender" that applies a trickle charge during store to keep the charge up rather than a "charger" used to actually recharge batteries such as a shop would use.
After such a long trip the battery should have been fully charged so if it was not you best have a dealer do a proper capacity test on on it. This is where you apply a specified load to it and allow it to discharge to an end point voltage and it must last a certain time or be replaced.
The other thing to consider is the car's charging system. Have a qualified technician check out the car before you get stuck somewhere.

[CP911]

Originally Posted by ianp622

Except the 2-series doesn't use a regular lead-acid battery, it uses an absorbent glass mat battery, which is explicitly designed to handle cycling (better for it not to be too deep, but certainly deeper than a lead acid).

It does? I looked everywhere for technical information on the 2-series battery because I wasn't sure if it was a lead-acid or lithium-ion battery, and I found nothing online or in BMW parts catalogs. When I lifted the trunk floor and looked at the battery, it said "Pb" right on the sticker. Is this really not a lead-acid battery?

[aaaaah]

I just drive the 235 every day to keep it charged...


The E30 i treat like the piece of shit it is.

[overcoil]

Originally Posted by CP911

It does? I looked everywhere for technical information on the 2-series battery because I wasn't sure if it was a lead-acid or lithium-ion battery, and I found nothing online or in BMW parts catalogs. When I lifted the trunk floor and looked at the battery, it said "Pb" right on the sticker. Is this really not a lead-acid battery?

Not having read through all the earlier post, I thought the different batteries for the car could be either absorbant glass mat or conventional lead acid? due to the dealer battery replacement price of near $500.

If the F2_ used a lithium type the price of a new battery would be approx $1000.

Last few weeks my car wasn't used for nearly 2-weeks when daytime highs were usually mid-teens F. started it over the wknd and got the Battery Discharge messsge. Went away after 20 mile drive.

[TajoMan]

AGM battery is some type of lead acid battery.
In AGM battery, acid is absorbed in multiple layer of glass sheets.
It makes the battery internal resistance very low (compare to conventional lead acid).

Advantage of AGM is that the battery can be cycled little deeper than conventional lead acid.

Also, the other main advantage is that it can be charged very quickly.
Since the internal resistance is so low, there is not much heat generated when the battery gets charged quickly with a lot of current.
That's why it is being used in conjunction with regenerative braking.
It cab be charged quickly during short deceleration.
Once the car starts, the battery gets charged up quickly.

It's also good for cold start because the battery can release a lot of current instantly.

AGM is maintenance free. No need to add acid. It can maintain charge for very long time. (I don't remember typical AGM battery life)

I cannot think of driving condition that you need to top up the battery frequently.

My wife's commute is just 15~20 minute city driving and the battery is still strong. (after 5.5 yrs, F25 X3)

[XutvJet]

I've owned my 2016 M235 for 2 years now. A couple weeks back we experienced some significantly cold weather for an extended period. One night it got to -10 and well I got to the office, my car gave me with the battery discharged warning and told me to keep driving. I drove around for another 20 minutes, but still got the warning. The car started fine 9 hours later after sitting in 0 degree weather. I researched the matter and learned a lot about this warning and late model BMWs and their energy usage.

1) Late model BMWs consume a lot of electricity due to all the electronics, especially in the cold when people like me are running heated steering wheels and seats.

2) Our cars run higher quality (and expensive) AGM lead-acid batteries due to the heavy electricity draw. These batteries are good, but take some time to fully charge. In cold weather, they can take a long time to charge and if you're only driving 10 to 30 mile trips in really cold weather, the battery charging system likely can't keep up.

3) BMW makes the charging system such that the battery only charges up to 80-85%. The reason being AGM batteries can be wrecked if overcharged. Also, undercharging greatly reduces their life.

5) The battery discharge warning is common place for those living in cold climates. BMW is pretty conservative with the battery warning setting and in some cases, the dealer can dial it back so it doesn't come on as often. Even when you see the warning, it doesn't mean the car won't start. The worst case would be you might not be able to run certain systems until there's adequate charge in the battery.

5) Running a battery tender like a $60 CTEK 4.3 Mus (specifically designed for AGM batteries) is highly recommended for those living in colder climates, especially when temps drop below 20 degrees over the long term. This will reduce the chances of the battery warning, keep the battery charged to a safe level, and extend the life of the battery. The CTEK takes quite some time to charge the battery, but that's how AGM batteries like to be charged.

[Viffermike]

Originally Posted by XutvJet

I've owned my 2016 M235 for 2 years now. A couple weeks back we experienced some significantly cold weather for an extended period. One night it got to -10 and well I got to the office, my car gave me with the battery discharged warning and told me to keep driving. I drove around for another 20 minutes, but still got the warning. The car started fine 9 hours later after sitting in 0 degree weather. I researched the matter and learned a lot about this warning and late model BMWs and their energy usage.

1) Late model BMWs consume a lot of electricity due to all the electronics, especially in the cold when people like me are running heated steering wheels and seats.

2) Our cars run higher quality (and expensive) AGM lead-acid batteries due to the heavy electricity draw. These batteries are good, but take some time to fully charge. In cold weather, they can take a long time to charge and if you're only driving 10 to 30 mile trips in really cold weather, the battery charging system likely can't keep up.

3) BMW makes the charging system such that the battery only charges up to 80-85%. The reason being AGM batteries can be wrecked if overcharged. Also, undercharging greatly reduces their life.

5) The battery discharge warning is common place for those living in cold climates. BMW is pretty conservative with the battery warning setting and in some cases, the dealer can dial it back so it doesn't come on as often. Even when you see the warning, it doesn't mean the car won't start. The worst case would be you might not be able to run certain systems until there's adequate charge in the battery.

5) Running a battery tender like a $60 CTEK 4.3 Mus (specifically designed for AGM batteries) is highly recommended for those living in colder climates, especially when temps drop below 20 degrees over the long term. This will reduce the chances of the battery warning, keep the battery charged to a safe level, and extend the life of the battery. The CTEK takes quite some time to charge the battery, but that's how AGM batteries like to be charged.

I began trickle charging with a CTEK MUS 4.3 (same as the BMW OEM charger) hooked up to my nearly three-year-old 228i a few weeks ago, after the warnings started coming on in colder weather since I only drive the car once a week now. The charger is safe for AGM batteries.

I also have a P3Cars multigauge, which includes a voltmeter, installed. Before the charger, the car held 14.8 volts consistently during operation.

I first ran the "Recondition" mode on the CTEK because the battery was falling below 12 volts after sitting a week, and the weather was quite cold (Teens to 30s for several days). On the first drive after that, the car ran at only at about 13.1 volts and would dip to the low 12s just before the car came to a stop at a stoplight.

I then set the CTEK's mode to cold since temps were still below freezing in the evening. On the next drive, the car ran at 13.3 volts; regen braking would lift that to 14.8, but it dipped back to 13.3 afterward with no dip just before the car stopped.

I'm now running the CTEK in normal 'car' mode (there's a motorcycle mode as well). Same deal: 13.3, with a spike to 14.8 under braking/coasting. After sitting right after starting the car, the voltmeter shows about 11.7 volts.

Basically, my car is now running at a significantly lower voltage than it used to, and frankly I'm not sure why. I chalk some of it up to the colder weather, but some of it may also be because of the AGM battery's difficult-to-top-up nature, as mentioned above. Since I'm selling the car, I'm not about to go on a 100-mile drive and put miles on it ...

[XutvJet]

^From everything I've read on the BMW forums and per the CTEK owner's manual, the only charging setting you should be running on a BMW AGM battery is the cold setting (snowflake symbol). Using any other setting could possibly damage the battery.

[Viffermike]

Originally Posted by XutvJet

^From everything I've read on the BMW forums and per the CTEK owner's manual, the only charging setting you should be running on a BMW AGM battery is the cold setting (snowflake symbol). Using any other setting could possibly damage the battery.

Hmmm. I'll physically check the battery this weekend. All the Recond mode does is add a short-term higher-voltage, lower-amp (15.8v, 1.5amp) phase just before float mode. The battery holds 12V fine since the CTEK gets to (and stays in) float mode.

[TajoMan]

Originally Posted by XutvJet

1) Late model BMWs consume a lot of electricity due to all the electronics, especially in the cold when people like me are running heated steering wheels and seats.

I think main power draw is from electric water pump.
(maybe electric steering as well)

Other than that, I cannot think of any significant source that uses much electricity.

[wdc330i]

As a data point, I've routinely had to replace my BMW batteries at the 4-year-mark.

[XutvJet]

Originally Posted by TajoMan

I think main power draw is from electric water pump.
(maybe electric steering as well)

Other than that, I cannot think of any significant source that uses much electricity.

Late model German cars are power hogs. Think of how integrated all the systems are. Yes, the electric water pump and electric steering consume energy, but then there's the auto climate control, heavy drawing audio systems, numerous computers processing lots of information, and heated seats and steering wheels (that takes a lot of energy). The way the alternator works is a bit wonky too compared to how most work as it sometimes is not prioritizing battery charge.

Given all of this and the type of battery used in these cars, it's quite common for the batteries to loose their charge once the temps drop consistently below the 20s. The battery sits in the cold trunk and AGM batteries are pretty susceptible to discharging when cold. That's why having a battery tender and using it every once in a while can go a long way. I got one only because I want to extend the life of the battery in my M235 and also my wife's newer Outback.

Now if you don't live in an area that doesn't see cold temps in the winter, then don't bother. The temps in Kansas City are now in the 30s and 40s and the battery in my M235 is at full charge and I haven't run the battery tender in 10 days.

[TajoMan]

Originally Posted by XutvJet

Late model German cars are power hogs. Think of how integrated all the systems are. Yes, the electric water pump and electric steering consume energy, but then there's the auto climate control, heavy drawing audio systems, numerous computers processing lots of information, and heated seats and steering wheels (that takes a lot of energy). The way the alternator works is a bit wonky too compared to how most work as it sometimes is not prioritizing battery charge.

It's all true for all cars these days. Not just German car.

Auto HVAC does not uses more power than manual HVAC. (HVAC blower uses up to 300 W at full blast, but not specific to Auto system)
Audio systems are pretty much all the same.
Most cars have fairly powerful computers.
Heated seats and steering are very common and it does not use that much power. (uses maybe 100 W for 10~15 minutes to warm up then lowered to maybe 50 W to maintain)

It's not just BMW or any other German cars uses more electricity these days.

One unique thing was the electric water pump. It can draw quite a bit of power. (~500 W)
(Most turbo charged cars use electric pump, but as the secondary pump. Not the main cooling pump)

Main problem for BMW was the alternator operation strategy. It just does not engage frequently enough for sake of fuel economy.
They fixed it several years ago but it maybe not enough for cold ambient.

Anyhow, I never had any problem with my wife's car for over 5 years.
Never had low voltage warning. (I live in Chicago, so it's plenty cold)
We had insanely cold winter 3~4 years ago. no problem. I guess I just got lucky.