Reason will only charge to 100%

[Robert Willoughby]

I asked BMW directly why the i3 won't charge to 80% when newer vehicles will. The reply I received is below. Of course I've received a few adverts for BMW newer vehicles now....

Thanks for contacting BMW ConnectedDrive about charging your BMW I3. I'm sorry to learn that you're still facing issues with this.

BMW electric vehicles with BMW iDrive before the introduction of BMW Operating System 8, you cannot set a charging target in the vehicle or in the My BMW App. Your vehicle always charges the high-voltage battery to 100 percent, provided the charging process is not interrupted prematurely.

I can confirm that your vehicle is running on OS 5/6 and it is not possible to update the OS as it is inbuilt.

I realise my response may cause some disappointment but I hope it clarifies the situation.

If there is anything else I can do for you, please feel free to get back in touch with us at any time.

Kind regards

TJ

BMW
United Kingdom
Tejaswini Koshti
Customer Support Executive
BMW Customer Support
Summit ONE
Summit Avenue, Farnborough
Hampshire, GU14 0FB

Tel: +44 (0)800 3256 000
Email: [email protected]
Web: www.bmw.co.uk

 

[eNate]

I'm surprised at the answer you received. I would have expected something more along the lines of "you should always charge your i3 to 100%" and "it was designed that way on purpose."

I'm an 80% guy myself and would love to have that as a built-in option, but so be it, I'll stick with timing my charges and not lose sleep over it when I go over.

I think the simple 100% message was deemed critical for marketing when this car first appeared with a 22 kWh battery and 80-something miles of range. Obviously BMW has changed their tune with the current crop of EVs. I wonder how hard it would be to add this as a simple option in an OS update – I mean, they've clearly demonstrated the ability to start and stop charging based on a schedule. But I'd bet doing so now might create some liability problems.

 

[Robert Willoughby]

All computers regularly have software updated with no risk of liability...seems a bit of a reverse event though... software updates slow the computers down until you need a new faster one. Software update on an i3 just to stop charging at 80% could keep the car battery lasting longer so you don't need a new one as quickly. Perhaps that's the disadvantage to the eye of a first line car dealership...they will sell a new model in a few years. Not good for any second hand dealer though or any present owner.

 

[eNate]

In terms of liability, I'm thinking of two things:

1. Introducing an 80% option now may open BMW up to owners who have suffered battery degradation requesting / litigating for new batteries, rationalizing that by not providing this option initially caused accelerated wear, and that by introducing the option now, BMW would be admitting to having made a mistake by not including it from Day 1.

2. Because the i3 doesn't offer OTA software updates, and because the OS update process is time, space, and resource intensive at the dealership, BMW doesn't want to open themselves up to this hassle, especially if they suspect the cost of installing the update will be (or could potentially be) on their dime.

Again, just speculation on my part.

 

[sailnavy]

The i3 battery was introduced when manufacturers were trying to figure out whether they should open the top xx% of the battery to the consumer or not. BMW chose to not open the very top of the battery. People love to argue about this, but the i3 was designed to be charged to 100% all the time. Tesla chose a different approach where they opened up the very top of the battery for occasional use. This isn’t a problem, it’s a battery integration design choice. Stop worrying about it. Different systems have different design philosophies.

 

[eNate]

The i3 leaves about 5% open at the top.

There's a slightly larger buffer at the bottom (false 0%).

Say what you will about BMW's motives and the state is battery technology in 2013, 5% buffer does but equate to 80% charge.

 

[Gonville]

I am based in the UK.

I have now a 120Ah - my third car - please see my tag line for history. Driving i3 for nearly a decade.

There are 2 things that are missed in those post.

1 - cell balancing doesn’t happen until charging is completed. I have posted many times my 60Ah on 100% showing 33 miles range after never charging to 100% for a year as a result of short top ups back in 2014-2016 on free council charge posts 7kW mostly. It recovered to 70 after being ABC all the time. (Picture shows the professor at Farnborough BMW HQ with his hand on the resistor that is used to burn down the highest cell in each pack. I was there I took that picture). Look up ‘passive top end cell balancing’. PS Tesla does active so stops at 80% all level. Newer LFPT Tesla are recommended to go to 100% as they are thermally more stable. 80% isn’t a good rule for anything.

2 - the i3 has the only thermal management system in any EV that uses highly efficient refrigerant to manage the thermal envelope of the battery. Expensive. Excellent. Unequalled. The newer I series models do have the Tesla method of using glycol cooling. Cheaper and therefore has to watch the top end temperature heating hence the 80% stop. Also on DC going beyond 80% is slower and blocks rapids.

As for ‘saving the battery’ by only going to 80%? Yes in a laptop. Yes in battery university with a single cell and no thermal management. In an i3? With a reserve top and bottom - see picture - no it doesn’t make sense to throw away another 20% just to stop it getting too hot at 100% (real).

Calendar degradation occurs in the i3 at 1-2% per annum. Chemical anodes. Does not matter how you charge it will still happen. See i3 at the top of Bjorn Nylands test chart - OK he is in Norway in New Mexico there have been issues with cars in 115f all day long. In the UK we have a group of 8,300 roughly quarter the UK registration and we have had only 1 cell replacement reported (3 cells Tim Organ) in 10 years. I can post a link to our store of BMW technical documentation if you wish.

Please charge to full as it was designed to do. And it’s nothing to do with software updates and yes going to Windows 10 probably stopped my old PC functioning as the hardware isn’t up to it.

 

[mfogarty]

I am based in the UK.

I have now a 120Ah - my third car - please see my tag line for history. Driving i3 for nearly a decade.

There are 2 things that are missed in those post.

1 - cell balancing doesn’t happen until charging is completed. I have posted many times my 60Ah on 100% showing 33 miles range after never charging to 100% for a year as a result of short top ups back in 2014-2016 on free council charge posts 7kW mostly. It recovered to 70 after being ABC all the time. (Picture shows the professor at Farnborough BMW HQ with his hand on the resistor that is used to burn down the highest cell in each pack. I was there I took that picture). Look up ‘passive top end cell balancing’. PS Tesla does active so stops at 80% all level. Newer LFPT Tesla are recommended to go to 100% as they are thermally more stable. 80% isn’t a good rule for anything.

2 - the i3 has the only thermal management system in any EV that uses highly efficient refrigerant to manage the thermal envelope of the battery. Expensive. Excellent. Unequalled. The newer I series models do have the Tesla method of using glycol cooling. Cheaper and therefore has to watch the top end temperature heating hence the 80% stop. Also on DC going beyond 80% is slower and blocks rapids.

As for ‘saving the battery’ by only going to 80%? Yes in a laptop. Yes in battery university with a single cell and no thermal management. In an i3? With a reserve top and bottom - see picture - no it doesn’t make sense to throw away another 20% just to stop it getting too hot at 100% (real).

Calendar degradation occurs in the i3 at 1-2% per annum. Chemical anodes. Does not matter how you charge it will still happen. See i3 at the top of Bjorn Nylands test chart - OK he is in Norway in New Mexico there have been issues with cars in 115f all day long. In the UK we have a group of 15,000 roughly half the UK registration and we have had only 1 cell replacement reported (3 cells Tim Organ) in 10 years. I can post a link to our store of BMW technical documentation if you wish.

Please charge to full as it was designed to do. And it’s nothing to do with software updates and yes going to Windows 10 probably stopped my old PC functioning as the hardware isn’t up to it.

Excellent post. Thank you for this information, it is much appreciated.

 

[Robert Willoughby]

Thanks. That's a clear answer and helpful.

Excellent post. Thank you for this information, it is much appreciated.

 

[eNate]

I don't understand any of these arguments.

Cell balancing occurs at some level below 100%. We've seen the data on this forum. I'm guessing nobody here is driving around with 30 miles range because of lack of balancing.

Cell balancing doesn't need to be performed daily. Driving around with out-of-balance cells negatively affects range, true, but is corrected at the next opportunity to balance and doesn't adversely affect the cells.

BMW can employ the most advanced cooling medium ever devised, but it's still via a plate cooler that has to work through the walls of the battery module box and cool the sandwiched, vertically stacked cells from the bottom. This is an inefficient but adequate way to cool a "brick" of heat, however it does not directly attack at the heart of the heat being created inside of each cell.

Compare that to Tesla where their cooling noodle is adhered to each individual D-sized battery cell directly (I know, I know,18650 & 4680, and different chemistry). Tesla who loves to ignore rules, and they still preach a charge limit.

Charging to 100% (or near 100%) stresses the chemical process, regardless of the heat. In fact, the extra heat the cell generates at the top is a byproduct of this stress. Even if it could be attacked directly with cold, that underlying exothermic process is still occurring.

None of this addresses that after charging to 100% indicated (95% actual capacity) there's now a fully charged battery just sitting there doing nothing. There's good consensus among battery experts that this is not an ideal condition for battery longevity.

That all said, BMW says charge to 100 and didn't give us any tools to do otherwise, so everyone should feel confident to go ahead and charge to 100. As an owner and user, do what suits your needs to make the car work for you.

But it's unproductive to pretend like 10 years ago BMW did something magical with this car and that the i3 battery is unlike every other battery and therefore there's no discussion needed. I have zero apprehension charging to 100 if I need the range, or even if the car unintentionally sits fully charged for a day. I have even less of a problem generally limiting mine to around 80. But I accept that either way, it probably won't have any great affect on my overall ownership experience.

But who knows, maybe it will prevent future pain, so what's the harm? Especially if I'm planning to hang on to this car for the long haul.

 

[Gonville]

I don't understand any of these arguments.

Cell balancing occurs at some level below 100%. We've seen the data on this forum. I'm guessing nobody here is driving around with 30 miles range because of lack of balancing.

Cell balancing doesn't need to be performed daily. Driving around with out-of-balance cells negatively affects range, true, but is corrected at the next opportunity to balance and doesn't adversely affect the cells.

BMW can employ the most advanced cooling medium ever devised, but it's still via a plate cooler that has to work through the walls of the battery module box and cool the sandwiched, vertically stacked cells from the bottom. This is an inefficient but adequate way to cool a "brick" of heat, however it does not directly attack at the heart of the heat being created inside of each cell.

Compare that to Tesla where their cooling noodle is adhered to each individual D-sized battery cell directly (I know, I know,18650 & 4680, and different chemistry). Tesla who loves to ignore rules, and they still preach a charge limit.

Charging to 100% (or near 100%) stresses the chemical process, regardless of the heat. In fact, the extra heat the cell generates at the top is a byproduct of this stress. Even if it could be attacked directly with cold, that underlying exothermic process is still occurring.

None of this addresses that after charging to 100% indicated (95% actual capacity) there's now a fully charged battery just sitting there doing nothing. There's good consensus among battery experts that this is not an ideal condition for battery longevity.

That all said, BMW says charge to 100 and didn't give us any tools to do otherwise, so everyone should feel confident to go ahead and charge to 100. As an owner and user, do what suits your needs to make the car work for you.

But it's unproductive to pretend like 10 years ago BMW did something magical with this car and that the i3 battery is unlike every other battery and therefore there's no discussion needed. I have zero apprehension charging to 100 if I need the range, or even if the car unintentionally sits fully charged for a day. I have even less of a problem generally limiting mine to around 80. But I accept that either way, it probably won't have any great affect on my overall ownership experience.

But who knows, maybe it will prevent future pain, so what's the harm? Especially if I'm planning to hang on to this car for the long haul.

That’s an excellent summary. Yes you don’t need to cell balance every day that’s true.

Just note that my car did only have a 35m range due to no cell balancing. That was a fact. I didn’t photoshop the picture. Recovered after charging to 100% for a few months.

I general I agree with your summary it isn’t something to get het up about just that not going past 80% religiously just isn’t a rule. For the i3.

But yes the engineering was excellent.

 

[eNate]

my car did only have a 35m range due to no cell balancing. That was a fact. I didn’t photoshop the picture. Recovered after charging to 100% for a few months.

That's interesting it's taken yours so long to recover.

What I've personally observed is it takes just one high SOC session to recover from mileage doldrums, ie real-world road trip range.

 

[alohart]

That's interesting it's taken yours so long to recover.

As those that the meeting that Gonville attended back in the day learned, the resistance of the resistors that discharge the cells at the highest voltage is so high that discharging, and thus cell charge level balancing for a battery pack far out of balance, takes a long time. This avoids any heating that would occur at lower resistances with faster charge level balancing.

 

[Mondomensch]

@alohart
What app/connector do you use to find out battery cell balance info?

 

[Darlouis]

What use case(s) cause the pack to be so far out of balance that it can take a few months of charging to 100% to rectify?
I checked mine a while ago after only charging to 80% (via home charging) for quite a while and it was still perfectly balanced according to Electrified app. I don't use it daily however so I have assumed, rightly or wrongly, that balancing may occur at < 80% and the pack is balancing during the days it's not in use.

Does frequent fast charging to lets say only 60% and using the car daily or many times per day cause the pack to become out of balance over time? as not resting for long enough at a high(er) state of charge where balancing occurs more quickly?

Seems like charge level is only one part of maintaining a healthily balancedbattery pack

 

[alohart]

@alohart
What app/connector do you use to find out battery cell balance info?

My iPhone running the free iOS mi3 app connects to my Vgate iCar 2 OBD to WiFi adapter to display BMS info. Apparently, the free Android Electrified app displays similar info.

 

[alohart]

What use case(s) cause the pack to be so far out of balance that it can take a few months of charging to 100% to rectify?

Pack imbalance is probably correlated better with the condition of the battery cells. If the internal resistance of a cell is higher than the others, more of the charging/discharging current passing through the cell would be converted to heat rather than to energy. The result would be that this cell would have a lower charge level when the pack is fully charged.

Cell capacities are never perfectly matched, so those cells with lower capacities won't have the same charge levels as those with higher capacities.

The temperatures of the cells will not always be the same, maybe due to their positions in the pack and how well cooling effects each cell. This temperature difference would affect the cell performance which would gradually result in charge level differences.

All battery packs with cells connected in series need to have the cells' voltages equalized, usually at a high charge level ("top balancing"). Our 2000 Honda Insight's BMS did not include cell charge level balancing, so the charge levels of its 120 battery cells gradually diverged over time. As a result, the usable capacity gradually decreased as the BMS prevented the cells at the highest charge levels from overcharging even though cells at lower charge levels could have accepted more energy, and when a cell's voltage decreased to the lower limit allowed by the BMS, other cells at higher charge levels were unable to discharge farther. When the usable capacity decreased to a certain level, a diagnostic trouble code (DTC) was stored and a battery pack trouble light illuminated. Honda's only fix was to replace the battery pack even though the battery cells weren't damaged but only needed their charge level's equalized. Insight owners believed that the battery packs that Honda was installing under warranty were packs rebuilt with used cells that had all been fully charged and thus were in balance. The battery pack in our Insight was replaced twice under the 8-year battery pack warranty.

A couple of enterprising Insight owners designed and build battery pack balancers that took advantage of the fact that NiMH battery cells aren't damaged significantly when occasionally overcharged. They merely convert the energy to heat, so the battery pack cooling fan was activated to prevent overheating during balancing. So charging continued until all cells were fully charged and thus their charge levels were balanced. I bought one of these cell balancers and began using it shortly after Honda installed my 3rd battery pack just after my battery pack warranty expired. This battery pack was still performing well 9 years later when we sold our Insight along with the cell balancer.

Fortunately, the i3 implements a much more sophisticated passive cell balancing protocol that seems to work very well.

Does frequent fast charging to lets say only 60% and using the car daily or many times per day cause the pack to become out of balance over time? as not resting for long enough at a high(er) state of charge where balancing occurs more quickly?

I wish that BMW had provided some guidance in this respect. I think the good news is that cell balance seems to be maintained well regardless of how the battery pack is treated. Gonville's experience with a badly unbalanced battery pack seems to be unusual, or maybe he's one of the few i3 owners who would have realized that cell imbalance was reducing the usable battery pack capacity.

 

[Ollie]

There are a **** ton of opinion's on this and it seems very few experts. For instance, I've been around long enough to have heard (for decades) the old tale that you can't put a battery on concrete (cement) or it will drain the battery dead. Anybody want to guess??? Yup, ding, ding, ding. All BS. I have a feeling a bunch of BS applies to the keyboard experts of now-a-days. For me. I'm gonna go with: heat destroys, excess heat kills. Slow charge all I can. 80% Fast charge when I need to, and let the battery management system do it's thing. Huh? I wonder if there is a clue in there. "battery Management system". But then my entire system runs on complete solar. I go from solar to battery storage to plugging in at night and pulling from storage batteries to charge I3 batteries. No grid, no gas, (ok a little grid when the weather is fuggly). A line from long ago. Don't get wrapped around the axle.

 

[Gonville]

That's interesting it's taken yours so long to recover.

What I've personally observed is it takes just one high SOC session to recover from mileage doldrums, ie real-world road trip range.

It only burns down one cell each time. So it does take a while if they are out of whack. Depends of course on how close the other cells are and are there a lot of very low ones I suppose.

 

[Gonville]

@alohart
What app/connector do you use to find out battery cell balance info?

I believe that we didn’t have that as a specific ‘thing’ - although the ‘eflow’ app by the bimmerlink folks does give info that I think I have posted. Gives max and min voltages and average so we can see how far out it is but not the actual 96 voltages. As far as I know. This shows that the voltages are out from the average by 0.001v which I think qualifies as balanced. So those charging to 80% should have a look at those 3 numbers?