After a full day driving with new battery, measured the voltage again.
when engine off/on

New battery:
12.7v/14.1v

Comparing old battery replaced:
12.36v/14.8v

It appears when battery ages, the battery capacity drops with voltage decreasing and the car adaptively increases the charging voltage to compensate that; If the holding voltage dropped to certain level, it doesn't meet the minimum requirement of some component, computer can throw errors, P0890 for our E70.

If the new battery is not registered after installed, it will be charged at high voltage than necessary and could shorten the life? It seems important to register battery to reset those charging adaptation values.

I am sure not professional in battery, just throw some thoughts here.

12.7 to 12.9 is common with a new battery. The battery has 6 cells inside. Each is supposed to provide 2.1 V. 2.1 x 6 + 12.6V. That is why they say 12.6 is a fully charged battery. In fact as noted a good battery will be a little higher.
You are supposed to let it sit for 30 minutes after the charge to check true voltage.
Even an old battery will read high if you check right after charging.

For the guys worrying if the system will notice if your batter does not have the right amount of reserve capacity or Amp Hours, you do know you can install two batteries in your system and your car will charge both just fine. The only limitation is the car will only charge till your weaker battery is fully charged. That is why they say if you want to install two batteries you need them both to be brand new and equal in size otherwise your stronger battery will never reach full charge.

I replaced my battery to Autocraft 95AH a year ago and registered it according to this thread. Now the battery seems to be underchanged everyday. If I don't drive the car for one day and two nights. The battery is dead.

Can anyone help? Link of details:
https://www.bimmerfest.com/forums/sh....php?t=1358913

One year old battery
 

If I encountered the situation you have described, and you've look for the obvious, namely stuff plugged into cigarette lighters, dome and courtesy lights the next thing I would do is take the battery to where I bought it and have it charged and load tested. This might help eliminate defective battery or charging system or narrow down areas of concentration. It is one of the easier things to do that will give you good information. Good luck.

E70 go through batteries fast if they aint driven a decent amount daily.

Problem is they only charge the battery when its stopped or coasting. Do what I did and code it to always charge the battery when running.

If N55, go into the 63BMO ECU and set IGR_CODIERUNG_MEV to nicht_aktiv
If N63, go into the 82BMO/83BMO/84BMO ECU and set IGRCODIERUNG to nicht_aktiv

4 years on this battery of mine instead of every year or year and half changing them out.

E70 Battery Replacement - DIY
 

[emoji848] very cool - might look in to this thanks man!

I just put a 95aH Varta in my N63 X5 but couldnt code 95aH - the only options were 90 or 105 - tried editing the trace file but ncsexpert flagged it so I just left it at 90 and registered via Ista+. Any experience trying to add a non-bmw battery of a rating not natively supported? Sorry if this thread is not appropriate to ask :)

https://uploads.tapatalk-cdn.com/202...f428ac16b3.jpg


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I had the same issue. I just bought the 105ah AGM battery at the dealer. It was the same price ($200) as the lesser AH at the auto parts stores.

All US N63 engines now use the 105ah. https://static.nhtsa.gov/odi/tsbs/20...53642-9999.pdf

Thanks for the feedback/info. I will assume that the battery wont reach full charge and so will trickle charge it once a month or so to be on the safe side.


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A capacity rating without a discharge rate is useless. How does BMW measure the battery capacity? Is it 90, 105, etc. Ahs? At a 20A discharge rate? 15A? 25A? We don't know.

How does the battery manufacturer you choose measure their capacity? At what discharge rate? Capacities of batteries change at different discharge rates. The industry standard is capacity measured at a 20A duschsrge rate. This capacity is called the C/20 capacity.

Please read post #115 in this very thread.

Thanks for the direction - seems a bit more complicated than just matching a number.


2012 E70 5.0iX