Caution on fully charging bmw e70 battery

[andrewwynn]

I'm curious now. I replaced my battery less than a year ago and did a few long trips (≈ 5@820 miles) I am very interested to see the SoC histogram. Also I didn't remember seeing more than one replacement registered but I'm also curious about that.

[E-series ftw]

Funny how BMW uses IBS to take the load off the electrical charging system during certain driving conditions, whereas many other manufacturers are using these inertia pulleys on their alternators. It's simply a one-way clutch or sprague that drives the alternator under acceleration and free-wheels during deceleration. It takes a lot of stress of the drive belt and attached accessories too I'd imagine. But, being a mechanic myself, they are suscepible to failure, as I've already seen on a few vehicles. I'm interested to see if BMW follows suit on this new design adoption. Maybe they already have, since I'm not too familiar with anything in or beyond the G series.

[Crowz]

Originally Posted by E-series ftw

Funny how BMW uses IBS to take the load off the electrical charging system during certain driving conditions, whereas many other manufacturers are using these inertia pulleys on their alternators. It's simply a one-way clutch or sprague that drives the alternator under acceleration and free-wheels during deceleration. It takes a lot of stress of the drive belt and attached accessories too I'd imagine. But, being a mechanic myself, they are suscepible to failure, as I've already seen on a few vehicles. I'm interested to see if BMW follows suit on this new design adoption. Maybe they already have, since I'm not too familiar with anything in or beyond the G series.

Oh they use those already on the some e92's, F30's, etc and they do fail.


I just like old school charge the freaking battery. I expect the battery to be fully charged when I turn the vehicle off. Not Russian roulette on battery charge.

[andrewwynn]

Here are the stats for my car.

As you can see most of the hours are spent from 60-80 but quite a lot are spent in 80-100.

My experience is the charge state is usually 80 ± 5%.

Most systems on the car use regulated voltage so you don't get dimming lights etc.

I have LED interior lighting so it doesn't change depending on voltage

[Crowz]

Actually all I see is just a tad over 82% which is wonderful... for a lithium battery. Not for an agm or lead acid battery.


Having done solar setups for several years I don't want to see those figures even if correct on a car battery that is supposed to be fully charged. Also I want my accessories to perform at full power too.


But again that's just me. I don't agree with their take on tinkering with the voltage.


The rear motorized hatch had even stopped opening one day at a grocery store in 5 degree weather when the car wasn't running. I had to close it and reopen it again. I imagine if I had of had the ibs disconnected around that time it wouldn't of happened.



I don't make long trips anymore and the car sits for long periods. I use a battery maintainer to keep it charged when not in use.


Disconnecting a fully charged battery and going somewhere and coming home and the battery being less charged than when I left is just dumb. Yes starting a car pulls it down a bit but were talking .1 volts tops and leaving with 12.8 volts in the battery and coming home with 12.37 to 12.5 is just wrong.


My E53's don't do that.



Also accessories one uses in the car should be provided with the correct voltage at all times while the car is running. The ibs system does not do that.


Again to each their own.

[E-series ftw]

I like how I can speed up my window motors on my e46 by burping the gas pedal for a second. I'm with you on the old school charging system.

[dreamalaska]

Originally Posted by Crowz

Yep thats the one.


I unplugged its lead.

Excellent - thank you for the post and clarification. I enjoy the engineering in my BMW but sometimes these German Engineers seriously overthink things. I curse the damned electric water pump. Great Engineering idea but horrible application in the real world. All for the sake of cheating an additional tenth of mile in mpg…there is absolutely no reward to that additional failure risk…


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[josiahg52]

Let's be truthful and accurate, the IBS exists to improve fuel efficiency. Every little bit helps and aids in them not having to pay the CAFE penalty. It's not about battery life or improving your life. Not saying it's right or any of you should be thankful for it.

The diesel does indeed seem to be different. Although it has an IBS, the profile and implementation is completely different, it seems.

[Crowz]

I'm just grateful it was easy to bypass.

[andrewwynn]

I spent a while trying to figure out where to code the IBS. No luck.

I have never witnessed any of the voltage related issues described and I've always been aware of the car trying to keep the battery at 80%.

My understanding is that many of the systems run through a vintage regulator but possibly not the windows so that will be an interesting one to test.

AGM batteries are supposed to be very sensitive to over charging, there are very detailed notes about stopping charge when they get to a certain current level when charging. A non issue when charging to 80%, also non issue for your charging system if it's an AGM charger, but if you charge at home then drive away with IBS disconnected, you're effectively putting it on a dumb charger that is just applying ≈14v, and that sounds like a recipe for damage. (Unless you have a flooded battery in which case, your reasoning is solid).

I've been monitoring reports for years and with IBS I'm seeing far longer battery life than the days before. Eg typical 3-5 years on e53 and 6-7-8 and more years on the e70.

My understanding was the IBS was as much for battery life as cafe standards.

Wife's '15 F10 actually shows when it's "dynamic braking" on the dash and she's does get very good mpg. 24/25 typical vs. my 20/21 in my e70. Same motor, but 1000-1500# less weight to toss around