alohart
Posts: 2121
Joined: Sat Nov 01, 2014 7:36 pm
Location: Honolulu, HI

Re: Warranty replacement of 12 V battery

Wed Nov 08, 2017 6:16 pm

TOEd wrote: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.
Our Swedish car was stored for 6 months each winter, so the battery was not used continuously. I usually kept the battery inside our apartment while the car was being stored so the battery didn't experience Sweden's winter temperatures.

One nice feature of AGM batteries is that their self-discharge rate is very low which makes keeping them on a battery maintainer not necessary unless the storage period is longer than a year. In fact, keeping a battery maintainer on an AGM battery could shorten its life. Just fully charge it and let it sit.

We have stored our i3 for 6 months each year since 2014. I didn't remove its AGM battery during storage and its voltage did not drop much. However, something has apparently caused it to degrade unlike my experience with the AGM battery in our Swedish car. BMW of Honolulu will be testing it on Monday, so I'll know more then.
Aloha,
Art

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

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

Re: Warranty replacement of 12 V battery

Fri Nov 17, 2017 3:41 pm

If still connected into the car...while not huge, there is a constant load on the battery, and it will discharge. Things like the alarm and proximity sensor (looking for the remote), the clock, are always running. On the alarm, you can turn off the interior sensor, but you can't turn off the other sensors.

I don't drive my ICE all that often, and when I do, it's used for about a 1K or more at a time, but in the interim, it sits on a smart battery maintainer that understands AGM batteries...I think it has easily kept this battery usable for probably 3-4 years beyond what is more typical for that type of car. I'm approaching 6-years on my ICE's AGM battery, and the battery seems fine. The first one died at about a year with my use pattern, and after that, I started to use the maintainer on it (a Bosch C7).

A dumb battery maintainer could damage the battery...a smart one, should not.
Jim DeBruycker
2011 535i x-drive GT, 2014 i3 BEV
Soon (hopefully!) A 2021 X5 45e will replace the above

alohart
Posts: 2121
Joined: Sat Nov 01, 2014 7:36 pm
Location: Honolulu, HI

Re: Warranty replacement of 12 V battery

Sat Nov 18, 2017 10:33 pm

BMW of Honolulu tested the 12 V battery in our 2014 BEV and proclaimed it to be functioning normally but they could not explain why the voltmeter that I had inserted into an accessory power port had measured voltages as low as 11.8 V when the car entered radio ready state after the doors are unlocked. They told me that the voltage at the power port isn't an accurate measurement of the voltage at the 12 V battery terminals. I don't agree, so I decided to measure the resting voltage directly across the 12 V battery terminals and then monitor the voltage when the car enters radio ready state due to my clicking the unlock button on my fob.

I recorded a short video of this test. I measured a resting voltage after our car had been parked for ~24 hours of 12.51 V which is reasonable. The longer our car is parked, the lower the 12 V battery's resting voltage. I then pressed the unlock button on my fob (the unlocking sound is audible in the video). Immediately, the voltage began dropping. Within a few seconds, the voltage dropped below 12.0 V before the DC-DC converter turned on (an audible clunk sound). The voltage immediately climbed to ~14.2 V which is normal for the charging voltage of the DC-DC converter. These voltages agree with those measured by my voltmeter at an accessory power port.

Should the voltage of the 12 V system drop so precipitously as an i3 enters radio ready state? The voltage of a 20 Ah battery would drop if the 12 V system is demanding so much power that the 12 V battery is incapable of providing the power without its voltage dropping or if the capacity of the 12 V battery is considerably lower than 20 Ah. A healthy 20 Ah battery at 77º F can power a 12 V starter motor without its voltage plummeting, so it's difficult for me to believe that various controllers booting could require as much power as a starter motor. Does this behavior seem normal?

I'm questioning how BMW of Honolulu tested our 12 V battery. If it has deteriorated as much as I think it has, an old-fashioned load test would have detected a weak battery. The Service Invoice states that the mechanic "connected ISID and found no faults related to" a weak battery. What's "ISID"?
Aloha,
Art

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

Bawareca
Posts: 48
Joined: Wed Apr 12, 2017 6:40 pm

Re: Warranty replacement of 12 V battery

Sun Nov 19, 2017 10:49 pm

ISID is the BMW diagnostic system.
From what you say the condition of your battery appears to be marginal. And because these batteries fail suddenly, i would replace it if I were you.

alohart
Posts: 2121
Joined: Sat Nov 01, 2014 7:36 pm
Location: Honolulu, HI

Re: Warranty replacement of 12 V battery

Sun Nov 19, 2017 11:40 pm

Bawareca wrote:ISID is the BMW diagnostic system.
Thanks for the explanation! If our 12 V battery is weak as I suspect, I wonder why ISID did not diagnose it as weak.
Bawareca wrote:From what you say the condition of your battery appears to be marginal. And because these batteries fail suddenly, i would replace it if I were you.
It is still under warranty, so I should not have to buy a replacement myself.

So far, I have been unable to convince BMW of Honolulu that our battery is marginal. Today, I sent my service advisor a link to the video and a description of the test I performed. I hope that this will result in further testing by BMW of Honolulu.
Aloha,
Art

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

Bawareca
Posts: 48
Joined: Wed Apr 12, 2017 6:40 pm

Re: Warranty replacement of 12 V battery

Fri Nov 24, 2017 5:32 am

The car itself will not report the battery is getting weak until an undervoltage condition has been recorded. It may not happen in a normal daily use, but if you leave the doors opened and the music on with the ignition off, it will happen.

alohart
Posts: 2121
Joined: Sat Nov 01, 2014 7:36 pm
Location: Honolulu, HI

Re: Warranty replacement of 12 V battery

Fri Nov 24, 2017 11:58 am

alohart wrote:Today, I sent my service advisor a link to the video and a description of the test I performed. I hope that this will result in further testing by BMW of Honolulu.
The shop foreman replied:

"So I took a look at the video and this is in fact normal behavior of an I3. Prioir to the High voltage coming online all of the electrical load involved with the "wake up" process of the vehicle is taken from the 20AH 12v battery. Due to the spike in current from all of the control units waking up at the same time it can and will cause a healthy 12v battery to dip below 12v for a period of time. That being said this car has the advantage of managing battery state of charge whether or not the vehicle is turned on, hence why they can get away with such a small battery. The vehicle is monitoring not only the state of charge of the battery but also the state of health of the battery on a continual basis, meaning that if the car deems it necessary it can kick on the high voltage and charge the 12v battery without any user input. It seems you are very knowledgeable about not only your vehicle but electronics as well, I think part of the confusion may be the term "radio ready". In reality the car is waking up the majority of the control units in preparation for someone to turn the vehicle on and want to drive. This gives it time to do a "pre-flight check" prior to ignition on."

If the behavior I've noticed is normal, the low resting voltage that I observe doesn't seem normal and could reduce the life of the 12 V battery. I asked the shop foreman whether this might be due to how little we drive which might not provide enough 12 V battery charging time. He didn't respond. I would like to attach an external charger to top up the low 12 V battery occasionally, but I don't want to damage the electrical system. I would rather not disconnect the 12 V battery before charging it. I can't see how using an external charger could damage anything if the high-voltage disconnect is disconnected. Any thoughts or suggestions?
Aloha,
Art

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

Bawareca
Posts: 48
Joined: Wed Apr 12, 2017 6:40 pm

Re: Warranty replacement of 12 V battery

Sat Nov 25, 2017 5:18 am

Another incorrect statement and lack of knowledge from a factory trained personnel.
-Once you open the car, or wake it up, only some of the modules will wake-up and the load on the battery will not be that high. In fact, the current drawn from the control modules should be under 1A. If the car is equipped with non-led interior lights that would be the biggest load.
There will be a substantial load when the ignition is turned on, but then the DC/DC inverter will be activated and 14V supplied, so the battery is not under load anymore.
-EME will monitor the state of charge and health of the 12V battery, but will not throw any kind of message that it has to be replaced. I may be wrong here, but i have never seen any message in a BMW prompting to change the battery.
-The DC/DC inverter will not be activated when the 12V voltage goes low, except if the car is connected to an EVSE.
If I were you, i would just leave the car open, with the ignition off for a while until some undervoltage codes are stored in various control modules. There will be nothing more the "foreman" could say.

alohart
Posts: 2121
Joined: Sat Nov 01, 2014 7:36 pm
Location: Honolulu, HI

Re: Warranty replacement of 12 V battery

Sat Nov 25, 2017 12:06 pm

Bawareca wrote:Another incorrect statement and lack of knowledge from a factory trained personnel.
Thanks for your comments! I was surprised that controllers booting could consume so much power that the 12 V battery's voltage would drop as much as I observe. Apparently, that's not true.
Bawareca wrote:If I were you, i would just leave the car open, with the ignition off for a while until some undervoltage codes are stored in various control modules. There will be nothing more the "foreman" could say.
I'll continue monitoring the 12 V battery's voltage. It seems far more likely that its voltage would drop below the level that allows the controllers to boot while it is parked in our parking space than when out and about. If this happens, plugging in our EVSE should allow the DC-DC converter to recharge the 12 V battery enough to start the car and drive to BMW of Honolulu. It seems that BMW of Honolulu isn't very proactive about replacing a weak 12 V battery and prefers to wait until an i3 won't start before acting.
Aloha,
Art

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

EVBob
Posts: 151
Joined: Tue Apr 18, 2017 6:06 am

Re: Warranty replacement of 12 V battery

Thu Aug 09, 2018 10:32 am

We are on 12v battery #3 in less than a year for our second i3 (replaced during CPO process in Jan, replaced again in April, replaced again today)
This particular i3, we drive everyday and have put 10K miles on it during our 7 months of owernship....

The service tech tried to pawn off that the i3's batteries die when the car is not driven enough and replacing it was sufficient...I told the service advisor it is driven everyday and reaffirmed this is battery #3 in less than a year, and in this instance the 12v died 20 minutes after it was driven (taking kids to the playground) - it should have been charged while driving. the service advisor is going back to the service tech and inform them to find the true cause....no one can have the luck of having three new 12v batteries going bad in less than a year...suspecting something going on with the dc-dc converter or how the car maintains the 12v batteries....but I guess we'll see....

...A little disappointed at BMW service that they would just let this fly.

Return to “Technical BMW i3 Discussions”