alohart
Posts: 2122
Joined: Sat Nov 01, 2014 7:36 pm
Location: Honolulu, HI

Warranty replacement of 12 V battery

Mon Nov 06, 2017 3:40 pm

If our 12 V battery is failing as I believe it is, BMW of Hawaii wants to replace it with a larger, heavier, flooded-cell battery used in other BMW models rather than the smaller, lighter, absorbent glass mat (AGM) factory battery. RealOEM probably shows the alternatives:

Description                                                    Size         Part #
Original BMW AGM-battery                        20 AH     61219321815
Original BMW battery (Warranty only)     40 AH     61217635788

The 40 Ah battery is used in F30 and F31 BMW's. I want the 12 V battery designed for the i3.

An i3 owner who wanted a larger capacity 12 V battery ordered the 40 Ah battery above but had to modify the battery tray and move the windshield washer fluid reservoir to install the physically larger battery. I would not want that done and would be surprised that BMW would do that just to install a warranty replacement battery that dealers are more likely to stock.

For those who have had their 12 V batteries replaced under warranty, which battery was installed?
Aloha,
Art

2014 BMW i3 Arravani Grey, Giga World, Tech + Driving Assist, Parking Assist, DC Fast Charging, JuiceBox EVSE

TOEd
Posts: 124
Joined: Sat Mar 05, 2016 5:15 am
Location: Toronto Ontario Canada

Re: Warranty replacement of 12 V battery

Mon Nov 06, 2017 6:37 pm

At 12,620 km and 5 months our new 2015 i3 12 volt battery was found to be defective during a condition based service oil change. No symptoms. Computer check indicated faulty battery. Replaced with smaller agm battery. No subsequent problems. Currently at 37,000 km (1 year and 8 months).

In a roll over or other serious accident agm battery is far less likely to leak. I would stick to smaller agm battery.

jadnashuanh
Posts: 5036
Joined: Thu May 22, 2014 2:07 pm
Location: Nashua, NH USA

Re: Warranty replacement of 12 V battery

Mon Nov 06, 2017 8:20 pm

AGM batteries are much better at extreme discharge than flooded cell ones. the i3 would tend to benefit from that. Now, there are probably larger AGM batteries that could be used, and a larger one would be less stress, because in normal circumstances, it wouldn't be discharged as much as the smaller one.
Jim DeBruycker
2011 535i x-drive GT, 2014 i3 BEV
Soon (hopefully!) A 2021 X5 45e will replace the above

TOEd
Posts: 124
Joined: Sat Mar 05, 2016 5:15 am
Location: Toronto Ontario Canada

Re: Warranty replacement of 12 V battery

Tue Nov 07, 2017 3:41 am

Forgot to mention that during past 40 years I have owned probably 20 agm batteries. They were used in a car, snowmobiles and a motorcycle. They usually lasted a year or two. The agm in my diesel smart lasted 2 and a half years. So I replaced it with a $10 flooded "blem" battery. Best $10 I have ever spent. 10 years and 170,000 km later it is still good (just checked it). Blems, for those unfamiliar with the term, are unlabeled seconds or defective batteries sold for cheap.

So I can appreciate your dealer suggesting a flooded battery. Not a bad option for those wanting long life from their battery.

jadnashuanh
Posts: 5036
Joined: Thu May 22, 2014 2:07 pm
Location: Nashua, NH USA

Re: Warranty replacement of 12 V battery

Tue Nov 07, 2017 2:52 pm

FWIW, the AGM battery in my GT is now over 4-years old and still working. The battery type utilized will depend somewhat on how the car is designed. An AGM battery tends to last longer when subjected to deeper discharge. In a typical ICE, the battery needs a big surge to start the car, then the alternator provides nearly all of the power. In my GT, they have the alternator on a clutch like an a/c compressor, and it doesn't always run, mostly when you let off on the gas pedal and are slowing. In the interim, it is relying on the battery. I think the i3 uses a similar technique. Also, an AGM battery will tend to use a slightly higher voltage during charging, and that can mess up a standard battery. On my GT, you can program the car to adjust to the type and size of the battery installed...I do not know if that's also true on the i3, but the curve and limits are different when properly optimized for the battery installed. On the GT, it also takes into account the age of the battery to handle expected degradation over time.

It's not always simple...today's cars are quite a bit more complex than they were even a few years ago.
Jim DeBruycker
2011 535i x-drive GT, 2014 i3 BEV
Soon (hopefully!) A 2021 X5 45e will replace the above

alohart
Posts: 2122
Joined: Sat Nov 01, 2014 7:36 pm
Location: Honolulu, HI

Re: Warranty replacement of 12 V battery

Tue Nov 07, 2017 3:40 pm

TOEd wrote:Forgot to mention that during past 40 years I have owned probably 20 agm batteries. They were used in a car, snowmobiles and a motorcycle. They usually lasted a year or two.
Maybe your AGM batteries were low quality or were being charged at too high a voltage. The charging voltage of an AGM battery is lower than that of a flooded-cell battery.

The Odyssey AGM battery in the 2000 Honda Insight that we sold in July was 7 years old, so under the right conditions, an AGM battery can have a long life. Our Insight's original flooded-cell battery failed after 3 years, possibly because the Insight's rather low-voltage 12 V charging system was better suited to an AGM battery.

Maybe the i3's AGM battery is low quality as well. If after the battery warranty expires and if the life of BMW's replacement AGM battery is no better than 3 years, I'll install a high-quality Odyssey AGM battery.
TOEd wrote:So I can appreciate your dealer suggesting a flooded battery. Not a bad option for those wanting long life from their battery.
The i3's 12 V charging system is set to charge an AGM battery, not a flooded-cell battery, so a flooded-cell battery might not last as long as it should.
Aloha,
Art

2014 BMW i3 Arravani Grey, Giga World, Tech + Driving Assist, Parking Assist, DC Fast Charging, JuiceBox EVSE

gt1
Posts: 350
Joined: Sat Nov 07, 2015 7:31 pm
Location: Baltimore

Re: Warranty replacement of 12 V battery

Wed Nov 08, 2017 11:03 am

In my opinion, a regular charging battery is not appropriate for i3, which has no conventional charger. A deep cycle (marine) type should be better.

alohart
Posts: 2122
Joined: Sat Nov 01, 2014 7:36 pm
Location: Honolulu, HI

Re: Warranty replacement of 12 V battery

Wed Nov 08, 2017 1:20 pm

gt1 wrote:In my opinion, a regular charging battery is not appropriate for i3, which has no conventional charger. A deep cycle (marine) type should be better.
I have a 12 V voltmeter installed in the power port under the entertainment system/climate controls so I can monitor the 12 V system voltage. The 12 V charging system does not allow the 12 V battery's voltage to drop below ~12.0 V (the low voltage limit is probably a bit higher), so the 12 V battery is never deep-cycled; when the 12 V battery's voltage drops below this low voltage limit, the DC-DC converter turns on to charge the 12 V battery using power from the Li-ion battery pack.

To the 12 V battery, the 12 V charging system looks similar to a conventional voltage-regulated alternator, so a standard 12 V starter battery in an i3 is probably superior to a deep cycle battery.
Aloha,
Art

2014 BMW i3 Arravani Grey, Giga World, Tech + Driving Assist, Parking Assist, DC Fast Charging, JuiceBox EVSE

gt1
Posts: 350
Joined: Sat Nov 07, 2015 7:31 pm
Location: Baltimore

Re: Warranty replacement of 12 V battery

Wed Nov 08, 2017 3:03 pm

I'm not an expert in the battery chemistry, but usually all features are compromises. The high current capability of the charging battery is probably built at expense of capacity or something else. And i3 doesn't benefit from high current.

TOEd
Posts: 124
Joined: Sat Mar 05, 2016 5:15 am
Location: Toronto Ontario Canada

Re: Warranty replacement of 12 V battery

Wed Nov 08, 2017 5:29 pm

:lol: I find info at this website useful:
https://www.batterystuff.com/kb/article ... asics.html

In my experience batteries last longer if used frequently. So I use the agm battery from my snowmobile in my boat during the off season. I live in Canada where the cold is very hard on batteries. I would guess that Hawaii doesn't get -40 C very often ;). So 1 to 2 years is what is expected for lifespan here. I also use a battery maintainer to top up batteries. It helps.

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