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      01-05-2021, 03:15 AM   #23
Leto1701
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Quote:
Originally Posted by MolarBear View Post
My local dealership (Leeds, UK) tested the batteries for me. It involved discharging and recharging the batteries - they printed an extensive report with a load of figures with voltages of each of the cells and different figures. All within range although annoyingly despite the low age and mileage (20 months or so, and 7000 miles) it was at 91%.
LiIon batteries don't age in a linear way. They loose some capacity quickly in the beginning and then the curve goes pretty flat. So I wouldn't worry about 91%. That might now hardly change for a couple years. This is how both my Tesla batteries behaved (before Tesla started to limit charging speed and power output for aging batteries to circumvent their own warranty).
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      01-05-2021, 03:25 AM   #24
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I know for a fact the BMW dealership left the car go flat for 8 months over lockdown in a car park without plugging it in before the sale. I suspect this might have something to do with it!
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      01-05-2021, 07:13 AM   #25
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Originally Posted by MolarBear View Post
I know for a fact the BMW dealership left the car go flat for 8 months over lockdown in a car park without plugging it in before the sale. I suspect this might have something to do with it!
The batteries don't go flat, at 0% there is a save charge level still in the battery. However, 8 months is a long time. It won't have helped the battery life. If fully charged before it might have just survived before turning into a brick. Wouldn't have bought it to be honest. 91% still sounds O.K. for the cells. The exposed "window" however should have hidden that from you. 91% visible would be O.K. for a Tesla (they allow full capacity use up to max. Voltage to advertise higher kWh and range). For BMWs more conservative strategy it is a concern.
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      01-05-2021, 08:30 AM   #26
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Quote:
Originally Posted by MolarBear View Post
I know for a fact the BMW dealership left the car go flat for 8 months over lockdown in a car park without plugging it in before the sale. I suspect this might have something to do with it!
There are explicit instructions from BMW according to which the i8 should be recharged every 6 weeks in the event of longer periods of inactivity.

"No. 61 03 98 (387) Battery recharging intervals for stationary vehicles, battery charging calendar and battery hangers (12 V battery, high-voltage battery unit)"

Including a "BMW Battery Calendar" for non US models and a "Battery Log Form" for US models.
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      01-07-2021, 06:03 PM   #27
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Quote:
Originally Posted by Leto1701 View Post
LiIon batteries don't age in a linear way. They loose some capacity quickly in the beginning and then the curve goes pretty flat. So I wouldn't worry about 91%. That might now hardly change for a couple years. This is how both my Tesla batteries behaved (before Tesla started to limit charging speed and power output for aging batteries to circumvent their own warranty).
Exactly.
Interestingly, my 2014 i8 with 70k mi is still at 100%, while the same old i3 with 30k mi is now at 93%.Different types of stress of course.
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      01-11-2021, 02:45 PM   #28
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Quote:
Originally Posted by BigT View Post
Exactly.
Interestingly, my 2014 i8 with 70k mi is still at 100%, while the same old i3 with 30k mi is now at 93%.Different types of stress of course.
Much higher stress on i8 battery btw, but they are designed differently to accomodate that.

However leaving a car to go flat over 8 months can't have done it any good.
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      01-18-2021, 06:29 PM   #29
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Originally Posted by JasH View Post
Much higher stress on i8 battery btw, but they are designed differently to accomodate that.
Frankly, I don't know enough about that, but at least the i8 doesn't allow the demanding 50kW fast charging, which is known as one major degradation factor.

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However leaving a car to go flat over 8 months can't have done it any good.
Yes, whoever allows something like this is a bit stupid and has only himself to blame or the pre owner.
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      01-20-2021, 02:27 AM   #30
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Quote:
Originally Posted by JasH View Post
Much higher stress on i8 battery btw, but they are designed differently to accomodate that.

However leaving a car to go flat over 8 months can't have done it any good.
It doesn't matter only how fast you charge regarding stress. It matters at which proportion of the capacity per time you charge. For the about 10 kWh of the current i8 battery the about 2,3kW charge is 0,23C. If you have a 100 kWh battery, you can charge at 22kW with the same stress on the battery. 1C is perfectly fine as charging speed. For the 43 kWh i3, 50 kW is just over 1C and no issue. Charging an i8 at 5C (50 kW) or more would. That's also why Tesla doesn't charge at more than 1C at the superchargers anymore for most of the time, no matter what kW they advertise. The Cells can't take it. At the moment, Porsche leads the pack there with what sustained charging speed the cells can take. If they will last we will see...
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      01-21-2021, 03:41 PM   #31
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It doesn't matter only how fast you charge regarding stress.
I didn't say anything about charging causing stress.
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      01-25-2021, 03:34 AM   #32
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I didn't say anything about charging causing stress.
Well it does. The i8 charges at max. 60 kW recuperating. That is 6C or something. Just something to be aware of. Taking 10C out of the battery is not an issue, if it isn't too cold. Those BMSes have a lot of parameters to keep in mind
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      01-30-2021, 06:29 PM   #33
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Quote:
Originally Posted by Leto1701 View Post
Well it does. The i8 charges at max. 60 kW recuperating. That is 6C or something. Just something to be aware of. Taking 10C out of the battery is not an issue, if it isn't too cold. Those BMSes have a lot of parameters to keep in mind
That isn't sustained though, there is a difference between regen or acceleration for 5-10 seconds versus charging for 30 minutes
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      02-01-2021, 05:25 AM   #34
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That isn't sustained though, there is a difference between regen or acceleration for 5-10 seconds versus charging for 30 minutes
It can be on long slopes. Just something to be aware of.
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      02-01-2021, 04:23 PM   #35
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Quote:
Originally Posted by Leto1701 View Post
Well it does. The i8 charges at max. 60 kW recuperating. That is 6C or something. Just something to be aware of. Taking 10C out of the battery is not an issue, if it isn't too cold. Those BMSes have a lot of parameters to keep in mind
It is really 60kW of regen? That's actually much better than I expected, my dual motor Tesla gets 72kW max regen and it's hard to get a feel for the full regen in the i8, since you have to apply the brakes and can't really feel what is regen or friction braking.
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      02-01-2021, 06:40 PM   #36
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Speaking of batteries and charge. My 2018 LCI i8 coupe intermittently gives the error ' Drivetrain. No restart'. The associated OBD2 code was 1D3702 Power Management, Battery: Faulty Charge By High-Volt Battery ( among others like Standby Current Violation) Then sometime the error spontaneously disappears and the car drives perfectly and can restart. Pat (Patonlinegarage) ,ever so kindly, suggested I consider the 12v battery . I just did a load test and the battery readings are ok with a state of health at 91%. Can it still be the 12v causing the error if all the measurements during battery testing seem fine? My car was bought in the UK and still under warranty but I shipped it to Trinidad and the local agents refuse to touch it.

Last edited by necropsyblade; 02-01-2021 at 06:45 PM.. Reason: add info
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      10-03-2022, 05:22 PM   #37
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Hello, so here in the USA 2016 i8 36k miles. I had an issue with my high voltage battery. Im told by the dealer they will have to replace all the high voltage cells. They refuse to mix pre lci cells with the older cells. So in theory when work is done i should have the full 11.6Kwh battery in a pre lci car. Also according to them BMW put a 10 year not 8 year warranty on the battery.
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      10-03-2022, 05:45 PM   #38
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Quote:
Originally Posted by tommyb13662 View Post
Hello, so here in the USA 2016 i8 36k miles. I had an issue with my high voltage battery. Im told by the dealer they will have to replace all the high voltage cells. They refuse to mix pre lci cells with the older cells. So in theory when work is done i should have the full 11.6Kwh battery in a pre lci car. Also according to them BMW put a 10 year not 8 year warranty on the battery.
It's 10 years indeed, so 2026 in your case; they don't count since the battery was installed….
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      10-03-2022, 09:01 PM   #39
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Yes 10 years from date car sold new
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      10-04-2022, 02:27 AM   #40
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Quote:
Originally Posted by tommyb13662 View Post
Hello, so here in the USA 2016 i8 36k miles. I had an issue with my high voltage battery. Im told by the dealer they will have to replace all the high voltage cells. They refuse to mix pre lci cells with the older cells. So in theory when work is done i should have the full 11.6Kwh battery in a pre lci car. Also according to them BMW put a 10 year not 8 year warranty on the battery.
My Swiss BMW dealer replaced batteries of my pre LCi but it was not possible to upgrade to bigger LCi battery pack. Curious to know, if it's possible for you to get the upgrade - this would be great!
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      10-04-2022, 07:04 AM   #41
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When was that? Because here in the USA they dont have any of the older batteries in stock. So all the batteries are post lci capacity. So Im getting all new higher capacity batteries. Have not yet received the car back. Im not sure how long it will take.
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      10-04-2022, 02:06 PM   #42
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Originally Posted by tommyb13662 View Post
When was that? Because here in the USA they dont have any of the older batteries in stock. So all the batteries are post lci capacity. So Im getting all new higher capacity batteries. Have not yet received the car back. Im not sure how long it will take.
HV Batteries were changed in Nov 2021, the car was built in Dec 2014.
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      10-04-2022, 04:59 PM   #43
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Check the full capacity the way they showed in the i3 tutorial. If it shows the 11.6 Kwh capacity then i would go to bmw and request them to change the % of available useable battery to at least what an lci car uses. However if it only shows 7.1Kwh... then they somehow still had old pre lci batteries in stock. Or you could request the dealership part numbers installed in your repair. That will tell you exactly which cells/capacity were installed.
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      01-02-2024, 07:03 AM   #44
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my BMW i8 hv battery sits around 79% remaining capacity, still useable but the electric range is very poor and i am considering upgrading the 20Ah cell packs to the newer 34 Ah packs.
the SME programming and the CSC communication structure were changed in the updated version but my estimated guess is i can change the bare cell packs to the 34Ah versions as long as i keep the original electronics .
the electronics will not see any difference except for the longer time it takes to charge and discharge the cell packs - the only electronic part in the cell blocks are the NTC's and i see no reason why they would change their values so after charging and changing the cell packs, renewing all gaskets ,making sure the equipotential screws are fitted correctly and refilling the refrigerant there should be no need for an EOS test to get it up and running - the voltages of the packs are the same , just the weight is a bit heigher and charging takes some more time but to my opinion it should work without any problems after refitting the upgraded HV battery .....
The car will never know the HV battery was removed as all electronics remains the same - i only have to write down and keep the cell pack serial numbers for comparison of the old / new cell pack locations.
I have to do some more investigation but i consider to use the 6 pcs 34Ah cell packs from a used recent BMW 530E SP41 HV battery - it would not make sense to use different cell packs for all different models because a modular setup is much cheaper for BMW .....
I would like to hear your opinion and comments about my idea - i will do some more investigation but at some point i will take the risk because this would be a relatively cheap option to upgrade my BMW i8 to the LCI level....

EDIT - i did some more research and discovered that the pre-LCI BMW i8 ( with 20Ah cell modules) has two CSC modules per cell module (total 12 x master) with two connectors with each 15 connections (total 30 connections) to the cell packs- they also have a total of 6 NTC's per cell pack ( 2x cell 1 , 1x cell 6, 1x cell 9 and 2x cell 16 of which the double + and - ntc's are probably only used for redundancy when one of the others fail...)
the i8 LCI version ( with 34 Ah cell modules) has only 6 CSC modules of which only one is the master and the other 5 are slaves and has only one connector with 24 connections to the cell packs.

the newer 740E / 330E models ( with 34Ah cells ) have the same setup as the newer i8 LCI version but they have 27 connections going to the cell packs instead of 24 (LCI i8) - so i will have to figure out how to connect the two old CSC modules of my pre-LCI i8 to the newer cell packs ( total of 30 connections old to 27 connections new).
As the setup op the cell packs is still the same ( 16 cells in series and 3 ntc's per cell pack ) this should be doable but requires good concentration, no mistakes allowed !

Any thoughts or comments , please post as i don't want to overlook critical things - thank you !

Last edited by Flasher; 01-24-2024 at 04:52 PM..
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