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2014 /May BMWI3 12volt battery 7 years old no issue

Fri Jul 16, 2021 8:27 pm

This post I’m putting on is for info with my experience with a car .i purchase an OM 12 volt battery from dealer wait 2month /$200 battery I hook up to NOCO genius2 to maintenance/storage to keep healthy battery bc my 7 old battery whitch I monitor any time I start a car is 14.23 volts all the time through cigarette lighter with voltmeter that purchase of battery was as precocious Bc i don’t want to have a brick go cart siting dead if a car dye I’m going to purchase over night a Foxwell 530 on amazon 160$ and register my new battery will be still cheaper bc BMW dealer is estimated my battery changed $550 is NewYork price my new battery on maintenance showing 13. 25 volts and sharing my experience talking to Bmw representatives in California they are saying my original battery can last to 9 years you may ask about my driving patterns I put only 20000 miles on car in 7 years I drive in winter in N Y I charge a car on 220 v in my garage once a week and I never keep car 100% charge try to stay in 80 % range I still can make 80 miles range my question is why so many people have a problem with 12 v battery I must be lucky one my driving a car is not a baby sit a car I beat a crab of it challenging every car on a road my all season tires a bold as slick but I have a set of Blizzacks for winter . 7years ago I sold my 911 and 944 to experience electric drive and I love it that experience bc I’m only 70 years young

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Re: 2014 /May BMWI3 12volt battery 7 years old no issue

Fri Jul 16, 2021 11:42 pm

Lesterbmwi3 –

A friendly note...

Your original post, as written, is nearly impossible to read as it lacks punctuation and formatting.

I think, with a better-written post, you might find your question receiving more replies.

Posts: 35
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Location: USA- NewYork

Re: 2014 /May BMWI3 12volt battery 7 years old no issue

Sat Jul 17, 2021 8:44 am

English is not my language sorry about my writing

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Re: 2014 /May BMWI3 12volt battery 7 years old no issue

Sat Jul 17, 2021 10:46 am

I think it comes down to the "Your mileage may vary" disclaimer.

I really don't know. I imagine the biggest stress in the 12 volt battery is hot and cold extremes, or maybe depletion due to long periods between drives. If I had to guess I'd think the load placed on this battery is fairly consistent for all users, just to keep the life support systems running when the car is parked. It's not like a car starter is drawing a heavy current from it.

Who knows? Maybe your garage has magical properties. My 2017 is going strong on the original battery, 45,000 miles, but I don't think I'm going to know it's dead until it fails me.

BTW the voltage you're seeing on your cigarette lighter socket reader is likely power being applied from the HV battery, as this circuit takes over once the car "wakes up."
Last edited by eNate on Sat Jul 17, 2021 1:20 pm, edited 1 time in total.
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Re: 2014 /May BMWI3 12volt battery 7 years old no issue

Sat Jul 17, 2021 11:16 am

i replaced my 2015 12v battery a month ago ( ~6 yrs old in May), since the battery tester SOH (with battery installed) was reading ~35% life remaining. Once I removed it and bench tested it, the tester said the state of health was much higher (?? maybe my connection was poor when testing in the vehicle). However, with the new battery installed, it looks like the system voltage (before the inverter turns on at 14.5v) stays above 12.5 volts whereas the older battery at times dipped to 12.00- 12.10 last winter, especially if the car was sitting for any length of time. I never got any strange error codes, but I was getting nervous about it and didn't want to take the risk. I also connected a small backup battery to the inverter posts in the engine bay to keep the computer systems powered up while changing the battery - worked like a charm, no disruption of power to the systems creating 'reboot' problems/errors (see other post for pictures).

So my opinion is that the my old battery may have been usable for another year or two, if I was willing to take the risk of driving until failure. I was also lucky in that someone ordered a replacement from the local battery supplier but never picked it up, so I got it at a big discount ($90+tax)!
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Re: 2014 /May BMWI3 12volt battery 7 years old no issue

Sat Jul 17, 2021 4:32 pm

The 12 V battery in our i3 manufactured on 1 August 2014 hasn't failed yet. I bought a replacement battery in April, 2019, but haven't needed it yet. Like your i3, ours hasn't been driven very much (less than 12k miles). Maybe that's the secret to a long 12 V battery life.

I haven't found a good way to detect a weak 12 V battery while it's installed. The voltage at the auxiliary power port is almost always the DC-DC converter's output voltage of ~14.3 V. For a few seconds before the DC-DC converter turns on, I can watch the voltage of the 12 V battery drop to as low as 11.90 V before the DC-DC converter turns on. This low voltage alarmed me at first, but it's been this low for over 3 years. The service manager at the local BMW dealer told me that this is normal for an i3 when its electronic modules are booting.

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