Quote:
Originally Posted by josiahg52
11.7 volts is not normal. It indicates a battery hovering around 50% SOC and a cell may have already reversed or be at a significantly lower SOC.
Open circuit voltage should be more than 12.7 volts. A fully charged battery in good condition should not lower more than 0.5 volts at nominal discharge rates. A 12 volt automotive battery that drops to 11.7 volts for anything longer than a second at anything less than a couple of hundred amps discharge rate is deficient.
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Key word is open circuit... I agree about that. But on the e70 it likes to keep a lot of things on even with key out of ignition.
I got a new battery a year ago and fully charged it and installed it. It was measured after key off 11.7, but if I let the car sit with the hood open, it went back to around 12.5.
My previous battery acted the same, but I was unsure of its age. It started with no issues on cold days of 10 F and this is a diesel engine!
I gave that battery to my friend to use in his beater e60 530xi.
On my friend's e60 nominal key out load with hood open, It's around 12.2. After sitting for a while it was 12.6. Some loads take time to clear out like on the e70.
My point is that the e70 has some really stupid programming that keeps heavy loads on for a while after key off. That's why op saw 11.7 and later 12.5.
The way bmw implemented power control on the e70 is really stupid... And that's why you can't really measure open voltage unless you physically disconnected the battery!