I only raised the issue of charging losses after tracking what my wall box was measuring and what BMW app was using in miles/kwh. My wall box was showing I was using some 12% more than what BMW said I was using. Discounting all of the possible variables. What it costs me is what my wallbox shows I use to charge my vehicle, not what BMW shows as my Kwhs used.

I think we beat this horse to death by now.

 

You should rather look into BMW data report from BMW site, there are 2 values in it: Energy taken from the charger and Energy stored into the battery. you can than directly see the losses during charging. Wall box consumption is on top, but should be really negligible.

 

Keep in mind that when BMW says 50% when stored for a lengthy period of time, they don't mean overnight. They mean two or more weeks. No reason at all to only use the bottom half of the battery when the car is in normal use.

To each their own. BMW says 30%-50% for long durations because it is best for the battery. If it is good for long term, you know it is good for short term too. We really do not know how long these batteries will last. Tesla's have only been on the road since 2012 and most have were sold in California with near ideal conditions that don't represent the rest of the country...particularly the south and hot climates. If you live in a cold or mild climate. Do whatever, it won't make much difference. If you live in a hot climate and easy to charge at home... I'm keeping mine below 50% in the summer when it is easy for me and no foreseeable inconvenience.

Exactly 👍😉 and BMW whatever you do to the battery it will survive the car's 20 yr life. They are as we say "idiot proof"

Battery may, but I bet the cooling systems and other stuff will die before the battery. The issue is will losing 10% of your battery affect you too much during road trips in 10 years. I think the issue is road trips when the car gets old. Majority of the degradation is out of your control unless you abuse it. That is why BMW says 80%. Not the best for the battery but a good balance for most. Although a multiple BMW owner, I like to keep my cars longer than average and don't take risk unless there is a reward. Charging high SOC is no reward for me. So to each there own.

both personal and anecdotal observations, and manufacturer's guidance, I see no reason to keep the battery hovering around 50% at all times.

Correct. Most data shows and a lot on previous post to this show significant degradation at high temperatures and high SoC. Basically lower is better as long as you above 10%.

For AC use max charging rate of the car onboard charger.

Every situation is so different it is hard to generalize. Need to account for wire in the wall if we are nitpicking. For me 32 amps @ 240V is the lowest power in the summer. At 40 Amps, my 6 AWG wire gets hot, charger gets hot, the charging fans in the car are running. I'm sure I'm putting undue stress on things too. In general going too slow 110V is wasteful, going max is wasteful. Everything in the middle is in the noise.

 

I charge to 85% about 3-4x a week. The rest of the week I only charge when needed which is rarely at all. So essentially the other 3 days the car sits between 20 and 85%. I’m a high mileage driver. If the battery last 10 years then it’s done it’s job. After that like all BMWs I expect the car to fall apart anyway 😂

 

So I've read Jeff Dahns studies about NMC 811 batteries which are in the i4 - he recommends to stay below 4.1 volts to maximize longevity and minimize degradation. He talks of longevity of 1.5 million kilometers if NMC811 batteries are regularly charged to 4.1 volts - which equals 83%.

When you connect the car to eFlow you can see the voltage per cell of the car. I've checked my car at 80% and at 90% state of charge. At 90% state of charge the cell voltage is 4.085. At 80% SOC the voltage is 4.045.
This means that the car charged to 100% would have a cell voltage of 4.12 - which would be around 85% "real" SOC per cell - implying a very large buffer, and it being completely safe to charge the car to 95% regularly. Have i missed anything?

 

This means that the car charged to 100% would have a cell voltage of 4.12 - which would be around 85% "real" SOC per cell - implying a very large buffer, and it being completely safe to charge the car to 95% regularly. Have i missed anything?

Yes, you have, two things:
1. For the *40/50 models you have 83.9kWh batteries (gross capacity). Usable 81.5kWh. That means a very small buffer which is beyond any doubt a bottom end buffer. So when you charge to 100%, you’re likely in the in the 99.xx% actual charge
2. BMW knows what’s best for the batteries in the cars they manufacture, and BMW recommends keeping the charge level between 10-80% for daily driving.

Lastly, it’s perfectly safe to charge the car to 100%, even though not ideal from a battery life perspective (per BMW recommendations), but safe.

 

I think the days of manufacturers holding back a lot of top end battery energy are over. They decided to let people use the top end if desired for long trips. That way they can claim higher range. So I will heed the BMW advice to routinely charge to 80% and only go to 100% when necessary.

I also am unsure that the voltages the app reports match the laboratory measurements of voltages. I’m sure BMW’s battery engineers are well aware of the research papers. They may be overly cautious, but they are the experts so I’ll follow their recommendations.

 

You need buy an OBD2 adapter that is compatible with eflow. BimmerCode for BMW and Mini - Supported adapters

EVScanner | The essential battery diagnostic app for your electric car.

EVScanner, the essential app for electric car owners, offers advanced battery health monitoring and personalized insights to enhance your driving experience.

geteflow.app

OBD2 port is under the hood/bonnet release on the driver side of the car. Google OBD2 port. Keeping an wireless OBD2 port attached to your car may in some rare cases allow hackers to access your car so use with caution in picking the right adapter and/or leaving it plugged in all the time. I live in a small town, no one knows how to use a computer, not less hack a car...so I'm not worried.

Search eflow on forums. This isn't the correct forum for eflow discussion.

 

Agree, however there is one comment in the manual about Sport mode will also prepare the battery for high performance driving. That could be the battery heating that I saw ?

 

I haven't read the manual fully, any where near and don't find it answers my questions at all, mostly.
Only my nephew's used that sport boost, I do 99% so far in Eco Pro (last week or so in Comfort as we're all recovering from a Christmas gathering virus).
That BMW only heats in sport tells me the preconditioning is mostly not a problem and clearly not something BMW thinks is worth describing for their car owners... Maybe as insignificant as the myriad of fuel additives mostly only young men buy at Canadian Tire?
BTW, if able please, where/what page did you find that in the manual? Searching the manual on my phone just now... The manual's search could benefit maybe from a Google search function update 🥴

 

Agree with you, I also drive +90 percent in Eco pro individual. It is more than two years ago that I read about battery heating in Sport mode. It might have been in some marketing material ?

 

Kewl

 

Wish the owner's manual had more on battery conditioning.

Agree. Most early adapters of EVs are geeks that want all the info. Maybe a white paper on how to maximize battery life and how bad each thing really is. Something that would at least tell us the chemistry enough to know if it is bad to go below 30% or not. As an engineer that has been censored by marketing, you need to keep the manual simple for the masses but other publications that a non-geek won't look at can go in detail. BMW is an enthusiast car brand, they have to expect we want the details.

EVs are starting to become an early majority. My BMW service advisor just bought a i4-Edrive 40. A 55 year old woman who is around cars all day but doesn't appear to know anything about EVs but EV curious. When you see dealership staff buy them, then you know they haven't had that many issues. I'm sure she gets a discount on repairs

insignificant as the myriad of fuel additives mostly only young men buy at Canadian Tire?

Additives work. My parents use them all the time. I don't use them, but I also don't get bad gas from the cheapest gas station in town with 50 one star reviews. If you get top tier gas once a few times a year, you will get all the additives you need. If you lucky enough to have a Costco, they only have top tier gas. I don't have a Costco so I just go to a Shell or Mobil occasionally to get my top tier gas with additives.

 

Agree. Most early adapters of EVs are geeks that want all the info. Maybe a white paper on how to maximize battery life and how bad each thing really is. Something that would at least tell us the chemistry enough to know if it is bad to go below 30% or not. As an engineer that has been censored by marketing, you need to keep the manual simple for the masses but other publications that a non-geek won't look at can go in detail. BMW is an enthusiast car brand, they have to expect we want the details.

EVs are starting to become an early majority. My BMW service advisor just bought a i4-Edrive 40. A 55 year old woman who is around cars all day but doesn't appear to know anything about EVs but EV curious. When you see dealership staff buy them, then you know they haven't had that many issues. I'm sure she gets a discount on repairs

Additives work. My parents use them all the time. I don't use them, but I also don't get bad gas from the cheapest gas station in town with 50 one star reviews. If you get top tier gas once a few times a year, you will get all the additives you need. If you lucky enough to have a Costco, they only have top tier gas. I don't have a Costco so I just go to a Shell or Mobil occasionally to get my top tier gas with additives.

Repairs? What repairs? And BTW just think of the time required to pump gas and get oil changes or a brake job! That sure adds up to buffer range anxiety and having to stop more frequently to top up (instead of fill up) on long trips (that are quite infrequent for most cars).
The real life anxiety for me now is will my DCFC "destination" be available and operational?
ALSO, just saying, charging stations need to be under canopies, same as gas.
Additives worth eh? Oh ya oh ya 🙄

 

How do you monitor the battery temperature ?

 

I don't. There is a symbol showing when the battery heating is activated. I trust it's true. I don't care about the temperature, I believe the car is doing what it supposed to do and heats it to the level needed. My car is always outdoors, so the temperature is as it is outdoors when I start. Also, if I just start a trip with a cold car it is obvious (can see that on the consumption display) that it consumes a huge amount of energy for about a half an hour. If I start the car when it is preconditioned and making the same trip it consumes considerably less, I mean totally normal values already from start.

 

You can see big icon of pre-condittioning/battery heating on the big media screen. When car heats the battery, the same symbol is shown in top right corner between other icons (icon in the middle) and same symbol is shown in consumption view:

consumption of battery heating is around 11kW and as i4m50Norway mentioned, car does not heat the battery when it reaches temperatures around -5°C anymore. Battery than continues to be heated by heat generated from the motor and heatpump, but resistive heating stops. I was also surprised to see that car allows full power/regeneration with battery bellow 0°C.

 

You can see big icon of pre-condittioning/battery heating on the big media screen. When car heats the battery, the same symbol is shown in top right corner between other icons (icon in the middle) and same symbol is shown in consumption view: View attachment 46948
consumption of battery heating is around 11kW and as i4m50Norway mentioned, car does not heat the battery when it reaches temperatures around -5°C anymore. Battery than continues to be heated by heat generated from the motor and heatpump, but resistive heating stops. I was also surprised to see that car allows full power/regeneration with battery bellow 0°C.

Mine is early 2022 build and likely will not get that preconditioning shortcut. Only way I know to do it is set a DCFC destination. Presume the system warms battery appropriately but I still almost always run the climate control when at a fast charger. I believe DCFCing causes significant warming so in hot weather running the AC surely helps. So especially important at temp extremes is my hunch.

 

On my car, I think it is only a symbol for Cabin pre-conditioning - the blue one, that started working after the 2024/4 release? Do you have any other indication of battery heating ?

I get this symbol when the battery heating is started:

This can pop up automatically if I have a DC charger as destination and the car considers that it's needed for best speed. There is also a text message popping up saying that the battery heating is in progress or something like that. I also have a manual, one time activation possibility which gives the same result, except if it is warm outside when it says something like "Battery heating is not possible because of ... (something)". BTW, this morning I did a quick test, the car was preconditioned for departure and the battery was at 63%, but it was very cold outside. I tested what happens if I start the battery preheating manually. It started even though the charge level was that high. So apparently, the level doesn't matter, the outside temperature does however matter, because when it is warm it won't start.

I have only monitored the battery temperature at the OBD port with software originally built for BMW iX3.
With that, I only have seen temperature increase while navigating to charger and once when I turned on Sport (Boost) in minus 20 celsius.

Can't you start it manually? I thought that it came with one of the latest updates to everyone.

Edit:
The blue symbol is not cabin heating.

If you mean that blue symbol then it indicates that the high voltage battery is too cold so the charging efficiency is reduced. If it is white it means that the battery is too hot, and again, charging efficiency is reduced.

 

BTW, this morning I did a quick test, the car was preconditioned for departure and the battery was at 63%, but it was very cold outside. I tested what happens if I start the battery preheating manually. It started even though the charge level was that high. So apparently, the level doesn't matter, the outside temperature does however matter, because when it is warm it won't start.

I needed to go somewhere immediately after work, in winter and needed full battery because it was below freezing outside. I do not have any charging available to me at work (not even a Level 1 outlet). I had somewhere over 90% in the battery (don't remember as it was a year ago) and pressed the manual precondition button on my way to the DCFC. It said it would not precondition the battery because the state of charge was too high.
So somewhere between 63 and 90 there is a limit for preconditioning even in cold temps.

The charging session started somewhere in the 20-30 kw range and got up to the 40's before tapering back down. I assume it increased as the battery naturally warmed as a byproduct of the charging process.

I made my trip and arrived with less than 10% so definitely needed the extra juice.

 

There is no solid, peer reviewed, study that indicates that charging to 100% and then removing the cord, harms the battery of EV’s at all. That is what I do.

 

There is no solid, peer reviewed, study that indicates that charging to 100% and then removing the cord, harms the battery of EV’s at all. That is what I do.

Page 67

https://mediatum.ub.tum.de/doc/1355829/document.pdf

 

Page 67

https://mediatum.ub.tum.de/doc/1355829/document.pdf

Page 57 (PDF Page 69) is data I have seen before for NCA batteries.

For the OP: If you only use 10% per day, then why don't you charge to 50% SOC daily? If you believe this chart, storing between 30-50% will have a little less degradation.

The shallow discharge is supposedly helpful as well vice bigger discharges.

That said, you can baby your battery and maybe it will have 2% more life than someone who rocked 80% daily. Who knows???

 

It’s actually quite hard to find reliable data or advice on battery degradation. Some recent stuff I’ve read implies that calendar aging is the biggest factor for most people. High states of charge at high temperatures is also bad news, as is allowing the battery to get very low and leaving it that way.

I think the best advice is to keep it around the 30-70 level if you can but to realise at the end of the day that it’s a car with a function to perform so going to 100% and fast charging if your travel plans need it is absolutely fine. Chances are that most of us won’t be keeping these cars for 10+ years so it’s definitely overthinking it to worry too much.

 

I charge to 100% every time I get a chance to plug the car in. I have only ever used AC Level 2 charging and I've seen enough evidence on EV forums and other sources that show that battery degradation under AC charging is minimal, so I'm quite happy to plug the car in when I get to the office and it's 100% charged by the time I leave. The car is 2 years and three months old and is due to to be returned when the lease expires in9 months. I've seen zero apparent degradation of range at all and I've charged to 100% from day one. In fact just a few weeks ago we did a repeat trip to Santa Barbara from LA, 92 miles to our destination. First time we did it we charged in Santa Barbara. This time we didn't charge in SB. The car started out with the GOM showing 200 miles, but because we were on a freeway both ways (184 miles) we got home with 40% left in the battery and the GOM read 110 miles.

 

I charge to 100% every time I get a chance to plug the car in. I have only ever used AC Level 2 charging and I've seen enough evidence on EV forums and other sources that show that battery degradation under AC charging is minimal

You keep repeating this claim without offering any reputable scientific evidence.

If only BMW had your good sense, they could stop telling people to charge to 80%. Or maybe they're just having a laugh at our expense. Or do you believe if you keep saying it, it will become true?

 

This just creates risks in buying a lease return as it is hard to tell how they are taken care of. In these cases a battery report is key, if that shows health good enough to give buyer piece of mind on longevity. Just depends on everyone use case. For me range is not an issue so I just stick to the 80% recommended since I bought it outright and want to drive it until the wheels fall off

 

This just creates risks in buying a lease return as it is hard to tell how they are taken care of. In these cases a battery report is key, if that shows health good enough to give buyer piece of mind on longevity. Just depends on everyone use case. For me range is not an issue so I just stick to the 80% recommended since I bought it outright and want to drive it until the wheels fall off

Buying any used car, ICE or EV has certain risks. A comprehensive PPI should always be done, covering everything - Battery health, brakes, electrical systems, tires etc. Used cars, by definition are degraded by their first owner's/lessee's usage. Leased EVs IMO have less potential for damage, especially because most leases have limited mileage conditions. My car will have less than 30,000 miles when it goes back. It is pampered, washed, serviced and driven rationally. It might need new tires and perhaps brake pads. Its overall battery capacity might have diminished by 2 or 3 percent, but other than that it will be a terrific buy for someone, at a ridiculously depreciated value.

 

My personal observation in my own car is that range in my car has not diminished in any perceptible way and it has been charged back up to 100% every single time plugged it in over the past 27 months. I'm not making any claims that aren't borne out on multiple EV forums. As to BMW "recommending" 80% charge limit, that is pure CYA (cover your ass, if that isn't well known British terminology) nonsense. If it was valid they would limit charging to a specific amount, leaving whatever headroom they felt worked. The reality is they can't have it both ways - quoting range figures, which means using the entire battery capacity from 100% down to 0% and then telling you should only charge to 80%. That's just asinine. If you want to limit the utility of your EV then follow their recommendations. Better still limit yourself to 60% or 50%. It has to be better by their logic. I personally don't buy it and I haven't experienced any noticeable battery degradation at all. In fact when my car went in for its 2 year service at BMW Santa Monica I specifically requested a battery health report and it came back at 100% of original capacity.

 

In fact when my car went in for its 2 year service at BMW Santa Monica I specifically requested a battery health report and it came back at 100% of original capacity.

It's very surprising to see that a battery health report would come back at 100% after 2 years of ownership. Batteries degrade naturally by time alone (regardless of charging type/history), and even after one year of ownership you're going to see at least 2% degradation, even if you left it sitting at 50% SOC the entire year without driving it. After two years, you'd likely see a minimum of 3%-4% degradation.

I'm not sure what the dealership did to test your i4's battery, but I wouldn't take that report seriously. That said, it won't matter to you because you'll be turning the car in and won't have to worry about the total degradation.

As far as charging to 100%, that's totally up to you and if your usual protocol is to charge it up and drive it the next morning, your car probably doesn't sit at 100% for extended periods. As long as you don't leave it sitting around for days at a time at 100%, it probably isn't having a hugely negative impact on your battery.

 

I guess when you lease/rent it’s just someone else’s problem down the road anyway. Would you do the same if you bought the car instead?

 

Before I bought any used car I'd do a comprehensive PPI and adjust my offer accordingly, or pass on the car if it was too compromised.
There's nothing hidden here and I don't see why I have to pamper my car so the next guy gets a pristine used car.

 

You should absolutely not be charging to 100% all the time regardless of method (AC or DC). Watch this video from the lead engineer who developed Tesla batteries.

EV Battery Health with Dr Jeff Dahn Dalhousie U

He explains very clearly why you shouldn't regularly charge above 75%-80% and presents the data to back up his opinions. He also explains that it's perfectly fine to charge to 100% when you need to, you just shouldn't make a daily habit of it.