Caution on fully charging bmw e70 battery

[Crowz]

Ive read the don't charge an agm's to 100% on bmw sites over and over. My Solar setups, lawn mower (its 100% electric with 4 agm deka intimidator batteries) and all my vehicles that have agm's stay at 100% when not in use.


My F250 which has two agm batteries that now over 13 years old and working flawless stay at 100% charge at all times.


Not buying the don't fully charge them.


Now that said they don't like fast charging. The volts have nothing to do with it. Its AMPS that kill agm batteries. What bmw is doing on these is keeping the charge level down so they can use the battery as an electrical dump. It's no different than using a coil for a wind power setup to dump energy into to act as a brake.


No ibs then no regen braking. I haven't noticed any real mpg difference since the change. There may be a mpg or two but if there is I'll happily trade it for the improved behavior.


Now is this for everyone?


That's debatable since if you have no aftermarket accessories (like my dashcam for instance) and don't have the rain guards on the windows like I do which puts a bit of a drag on the windows motors then you probably will never know what's happening so its probably not worth the effort in the matter.


Having a battery at 100% with x drain on it will sit for longer periods of time and still crank than a battery at 80% or less for obvious reasons.


The car seems "happier" with it unplugged. It seems to be peppier motor wise too. Again I can't put that down as fact. But its more fun to drive disconnected than connected to me. But I cannot in all honestly say this isn't just in my head.

[andrewwynn]

I didn't think it's a 100% charge issue it's continue to charge when at 100%. That said, the pre '07 bmw just charged like all cars for the party 100 years but I did notice as mentioned, just getting feedback on the forums, people getting a longer run on their e70 vs. e53.

That said you clearly are In a different class regarding batteries than the regular Joe.

I like being able to check the histogram and never been surprised that the battery is 80% full on average. Unless you are deep cycling the battery is a non issue but I'm a little surprised at how much the car will run off battery when at idle like you noticed.

Good that you posted though; it's far more complicated to diagnose a weak alternator with IBS! Even the bmw repair manual says "it could be this or that". I think you may have discovered the best way to tell: unplug the IBS and monitor realtime voltage!

[Clavurion]

Originally Posted by 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%.

If the vehicle uses intelligent battery charging (leaving the charge to 80%) the coding option is on engine control unit. Depending on DME/DDE version the coding option is a bit different, something with IGR (Intelligent Generator Reglierung).

[andrewwynn]

IGR is the phrase I was looking for


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[Crowz]

https://www.bimmerfest.com/threads/i...ntrol.1318861/

[newb2bimmer]

I did tickle charge the E70 to full charge a few times, if you wait a couple of hours it is all fine. I'm surprised how lowly charged it normally keeps the battery.

[andrewwynn]

As long as chase from the B+ point under the hood the IBS will track the changes

[Clavurion]

Originally Posted by andrewwynn

As long as chase from the B+ point under the hood the IBS will track the changes

IBS is on the battery ground wire so when you charge the battery the charger negative side has to be on body ground, not directly on battery terminal. The positive side can be connected to battery terminal, that does not matter.

[andrewwynn]

This is true but moot point who'd open up the battery bay vs. the hood.


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[Clavurion]

Originally Posted by andrewwynn

This is true but moot point who'd open up the battery bay vs. the hood.

That's of course true and the only reasonable way if you are not over thinking old school and connecting directly to battery. My main point was just to emphasize what keeps IBS on the loop.