[HighlandPete]

Originally Posted by Wires

My case was most likely the cold temperature. You just cannot charge a cold battery as fast, but at the same token, I've never seen this with any other vehicle. Is it because it didn't happen, or just the vehicle didn't toss the ominous "you are going to be stranded soon!" message. Could be the latter, with BMW being more proactive with warning you.

I tend to agree with the idea BMW are being proactive, giving us warnings. Rather than be in ignorance (or a slow crank), like most vehicles, when the battery is down on charge.

[chiefneil]

Originally Posted by Wires

My case was most likely the cold temperature. You just cannot charge a cold battery as fast, but at the same token, I've never seen this with any other vehicle. Is it because it didn't happen, or just the vehicle didn't toss the ominous "you are going to be stranded soon!" message. Could be the latter, with BMW being more proactive with warning you.

-30F is pretty extreme. Especially with the battery in the trunk where engine heat isn’t going to warm it up, two short 20-30 mins driving stints probably gave it a negligible amount of charge.

For sure every car is affected the exact same way. Other manufacturers don’t have access to special magic batteries, but non-premium cars do likely skimp on battery monitoring technology. BMW with the IBS (intelligent battery sensor) and SOC (state of charge) tracking is probably more proactive about giving warnings. Ignorance is not bliss when it comes to getting stuck in -30F weather!

I keep a portable jump starter like this in the trunk for emergencies: https://www.amazon.com/NOCO-GB40-Ult...s%2C190&sr=1-4

Also check out this article: https://batteryuniversity.com/learn/...w_temperatures

Now where I would fault BMW is that it never seems to charge the battery about 75% or so and that’s understandable under normal circumstances. But during sub-zero weather it really should charge to 100% (if it doesn’t, I don’t know).

[Sigtran]

Originally Posted by chiefneil

Now where I would fault BMW is that it never seems to charge the battery about 75% or so and that’s understandable under normal circumstances. But during sub-zero weather it really should charge to 100% (if it doesn’t, I don’t know).

Exactly. If temperatures are going lower, i.e. winter time and lower temperatures, SoC target should be at least 75%, maybe even 90% to be on safe side. Most important thing to most drivers is reliability - it just doesn't make a sense that with 2-3 years old battery and regular daily driving of total ~1hr (except weekends, especially winter typically not driving) I should be using external charger.

My wife, who owns a non-premium german car half of the price of my BMW, never ever has to do external charging, SoC is typically 90%+ (12.6V-12.7V, non AGM battery) and she is driving less miles and less often than myself.

IMO, it is a BMW engineering design fault. Period. Even worse, they don't want to admit it, nor want to give advanced users option to tweak the SoC target value withing some safe limits!

[Wires]

Originally Posted by chiefneil

-30F is pretty extreme. Especially with the battery in the trunk where engine heat isn’t going to warm it up, two short 20-30 mins driving stints probably gave it a negligible amount of charge.

For sure every car is affected the exact same way. Other manufacturers don’t have access to special magic batteries, but non-premium cars do likely skimp on battery monitoring technology. BMW with the IBS (intelligent battery sensor) and SOC (state of charge) tracking is probably more proactive about giving warnings. Ignorance is not bliss when it comes to getting stuck in -30F weather!

I keep a portable jump starter like this in the trunk for emergencies: https://www.amazon.com/NOCO-GB40-Ult...s%2C190&sr=1-4

Also check out this article: https://batteryuniversity.com/learn/...w_temperatures

Now where I would fault BMW is that it never seems to charge the battery about 75% or so and that’s understandable under normal circumstances. But during sub-zero weather it really should charge to 100% (if it doesn’t, I don’t know).

Not disagreeing with that at all. The car was at 10C in the garage, and 15 minutes is a pretty short commute. Dealer had installed a DTEK charger (integrates into the front grill with a detachable power cord), so the "fix" was quite simple. It sounded like they installed them right at receipt of vehicle to the lot. It was added to the purchase price of the car (non negotiable), most likely to address this.

[HighlandPete]

Originally Posted by Sigtran

IMO, it is a BMW engineering design fault. Period. Even worse, they don't want to admit it, nor want to give advanced users option to tweak the SoC target value withing some safe limits!

I express it as a design limitation, rather than a design fault. Same as I see design limitations to the use of run-flat tires, or limitations in use of the advanced HVAC systems.

Just a few users will ever see those limits, let alone look deeper into their function.

The APM (Advanced Power Management) is continuously checking the SOC and battery condition, has values BMW are using to protect the user for startability.

For example BMW indicate for AGM batteries under APM.
Startability limit is approx. 30% state of charge at 15 °C.
Startability limit is approx. 50% state of charge at -15 °C.

APM will be protecting those values, in extreme working conditions. If we don't happen to drive enough over time, to even allow that to happen, we'll get a warning.

I do wonder how many users don't actually get an engine start, due to BMW's energy management's function. Rather than a fault.

[Sigtran]

Due to more "working from home" and also a bit because of a BMW "design limitation" to decide to keep SoC relatively low, now I am getting into a bit of a trouble...

Since doing much less driving for past several months (typically driving mostly only weekends, on average maybe 100 km), last weekend car really struggled to start (I checked voltage previously, it was only 11.7V before starting), and even after 1.5hr drive, next day voltage was just 11.8V, struggling again and throwing a Low Battery message blabla again... I don't know which current alternator supply to battery in low SoC, I can guess less then 10Amps, maybe only even 5Amps or less...

I worry that soon it will not be able to start, especially with lower temperatures coming. Not to mention it is very bad for battery lifetime to be in very low SoC.

Since parking place is closed garage place but without plug-in electricity socket available, only way seems to be the hard way to take battery completly out of the car and charge it at home (I just purchased CTEK MXS 5.0 for purpose).

Question: Would there be any problem if car stay without battery for some 24-48hrs? Is there any problem expected after I connect it back, since it has IBS and as many modern cars it is also full of electronics that don't like to be disconnected from battery?

[dangerus_car]

Originally Posted by Mr Podman

You're fine.

You run in eco mode so you can save gas but have your starter motor suck your battery and wear itself out at every traffic stop.

For your own curiosity, measure battery voltage while the car is running. If you see readings around 14 volts it means your charging system is working properly.

so eco mode actually wear out the battery faster than in comfort/sport mode? meaning drivers sacrifice battery for better gas mileage?

if so, how does eco mode work?