Charging Best Practices

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jwzimm

jwzimm

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Hello all,

I am sure this has been discussed previously but I have not seen anything definitive.

I have had my SE for a couple months now and I got to thinking about best practices with respect to charging. I installed the level 2 FlexCharger in my garage and use that exclusively. My standard practice has been to plug in the car as soon as I return home in the afternoon each day. My typical commute is around 20 miles round trip and I normally arrive home with between 70% and 80% charge remaining. I have read other EV drivers practice a more concerted battery cycling regimen to help with battery wear but I have also heard that BMW/Mini recommends "ABC" or Always Be Charging.

What is the collective opinion/suggestion for charging best practices to ensure the battery is properly maintained and will last as long as possible?
 
Excellent question.
I charge mine just like you describe - 40-mile trip, charge upon arrival home. Next day, 50-mile trip, charge when home. I've asked my sales manager if there's a problem with that, and he assures me that this is best practice. He's confident that there are enough safeguards in the software to prevent any problems. I always know that, should an emergency trip thrust itself at me, I'm always fully charged.
 
The Samsung SDI 94Ah i3 and CATL MINI SE variant should be using NCM 333 (111) so it's extremely conservative. The Samsung 94Ah has a lifespan of 3200+ cycles (estimated 4600 from B Samples) so if you charged from 0%-100% SoC every single day it would take 8.767 years to get to 80% max original SoC.

One driver reports 5% degradation over 3 years. And another has 4.23% after 83,297 miles (134,055km) on his 2018 BMW i3s.

Higher nickel content will allow for greater energy (and range) but at the cost of accelerated degradation. Higher cobalt concentration and manganese to a lesser extent provide lithium ion stability. Drive it a few times and charge all the way to 100%. If you really want the most out of your Level 2 charging you can also derate to 15A-25A.
 
The collective knowledge of this forum (for the most part) agrees with "always be charging". I state that simply from reading many posts about the battery the past year and a half from this group of fine drivers.
 
Thanks for the feedback.

I am interested in your comment about derating the L2 charging. I was led to believe that charging at max rate was the most efficient option. Would setting the charging rate to a lower level better serve battery health? Since I have lots of time after I get home before I will be heading out again I normally do not need the fast recharge time so if there is an advantage to charging at a lower rate it would be no issue for me.
 
I have over 42,000 on my two year-old SE and notice no range drop. I charge to 100% every day, driving about 500 miles per week. When I got my SE I asked the dealer and was told charging to 100% is fine, even DCFC.
 
jwzimm said:
I am interested in your comment about derating the L2 charging. I was led to believe that charging at max rate was the most efficient option. Would setting the charging rate to a lower level better serve battery health? Since I have lots of time after I get home before I will be heading out again I normally do not need the fast recharge time so if there is an advantage to charging at a lower rate it would be no issue for me.
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Charging at the max 7.4kW is totally fine assuming the electrical work is properly installed. Derating just lowers the overall heat for all electronics/battery and leaves a little voltage buffer for extreme hot/cold. I have yet to really look into the AC -> DC rectification process on the onboard charger.

My main reason for derating the Level 2 EVSE is because I have solar PV to maximize renewable energy.
 
On average I drive about 90 miles per week, and charge once per week. I'm in the camp of reducing charge cycles when I can and not letting it sit at a high state of charge for too long...
 
teslarati97 said:
Charging at the max 7.4kW is totally fine assuming the electrical work is properly installed. Derating just lowers the overall heat for all electronics/battery and leaves a little voltage buffer for extreme hot/cold. I have yet to really look into the AC -> DC rectification process on the onboard charger.

My main reason for derating the Level 2 EVSE is because I have solar PV to maximize renewable energy.
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I need opinion if is advisable do not plug charge a battery after a trip right away bc battery is hotter at that point once cooldown is taking charge better as I don’t have a problem with temperatures my car is always in garage 60-80 ‘and I charge a car from 12-8am only L2 my battery is quite cool at that point at those hours my energy provider pay me to charge my SE as well for 6 years I 3 .
 
I refuse to coddle my SE's battery. MINI surely assumed that any car with such a small range would be fully charged often. Rather than advise owners to charge fully only when planning a long trip (eg. 100 miles in this EV), MINI likely sized the top-end buffer to a larger percentage of the total battery capacity than that in big-battery cars. I believe MINI traded longer EV range for greater battery protection.

upload_2022-9-6_18-55-37.webp
 
Perhaps coincidentally, there was a post in the SE forum at the MINIF56 group last week that brought up a similar subject, and got a reply that set off some flags for me.
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9ADE314C-5DA9-4354-8145-823C5CC5AA1B.webp
42EBC532-E558-4E3A-B56D-1AB9D72D2F10.webp
 
Watched a Toyota tech who deals with batteries in hybrids talk about this on youtube.. just a random guy talking on the internet so it's a guide but it made sense to me:

Basically heat, and keeping the battery at a high charge or low charge for long periods of time is not the best for long term battery health. As you drive it creates heat..and as you charge it creates heat. I think Nissan Leaf owners generally follow the 20%~80% rule (yes I know there's additional capacity at 100% indicated). If you need 100% in the morning, then time the charger to charge during the cool night to top off 100% right before you go drive to avoid long periods at 100%. Avoid charging or especially rapid charging (which causes heat) right after a long drive or...extreme summer heat. Don't park over a super hot parking lot all day.. try to get shade whenever possible..

just the basics so.. I try to follow all those rules in hope to baby the battery along. Probably overkill but that's what I do. But who knows.. that's just the theory I try to follow.
 
I try and keep my 2023 below 90 and above 20 when not in use. I do not have home charging and use the local chargepoints when needed. I have noticed in my 2023 owners manual it says if possible to keep the battery between 10-80%. On my mom’s 2022 if I remember correctly, the owners manual recommends always charging to 100%. Because of this conflicting info from MINI/BMW I follow the general EV battery charging rule of 80-90%.
 
teslarati97 said:
For the AGM 12V accessory battery, yes there can be corrosion. For the high voltage battery in the SE, it is fine.
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Yeah but if the 12V goes flat while the HV battery is below zero, the interlock turns on and bricks the car. Even when the HV goes to “zero,” there is plenty left to maintain the LV battery’s SOC.
 
The guy in the screenshoted post above is correct but he is not appreciating the buffers BMW put at the top and bottom of the pack. I suspect the bigger buffer is at the top.
If we used our Mini daily we would plug it in every time we got home and allow it to charge every night. And for a time we did.
But a change in circumstances means the Mini only gets used 2-3 times per week, mainly at the weekend, so we plug it in the night before we know we will use it, let it charge to 100% and then we will use it the next day so it won’t be at 100% for long. We’ll then use it for 2-3 days (without charging) and the charge will drop to 50-60%. We will leave it unplugged until we again get to the night before the next 2-3 day session of use occurs.
We do it this way to limit the amount of time it spends at 100% and in fact is sitting just above mid pack most of the time. Yes I know I just said there are buffers and I don’t think our actions are required. But it’s no inconvenience to us so why not… maybe we’ll gain a couple of percent of extra health over like 8 years, or maybe not.
Last time I used the ODB2 dongle and mi3 app it suggested our battery SoH was 100%. However we only have 3,500 miles on it and 9 months of life.
 
bmartinez028 said:
I have noticed in my 2023 owners manual it says if possible to keep the battery between 10-80%. On my mom’s 2022 if I remember correctly, the owners manual recommends always charging to 100%
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I just realized the addition on (IIRC) page 238! I’d been using a pdf of the 2022 since I ordered my car, and hadn’t bothered with the Motorer’s Guide version once my app was unlocked upon delivery. I don’t see an ABC recommendation in the ’22 manual, but nowhere does it suggest the 100% and 10-80% that the ’23 book does. I’m inclined to believe it’s there as a CYA after the Bolt fiasco.
 
SameGuy said:
Yeah but if the 12V goes flat while the HV battery is below zero, the interlock turns on and bricks the car. Even when the HV goes to “zero,” there is plenty left to maintain the LV battery’s SOC.
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One person managed to restore a i3 REX from auction by connecting a BMW 335i 12V battery in parallel to then J1772 charge the HV battery.


Matt007b said:
I think Nissan Leaf owners generally follow the 20%~80% rule (yes I know there's additional capacity at 100% indicated).
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Nissan LEAF owners have bigger things to worry about such as passive cooling for the HV batteries (all generations).

bmartinez028 said:
On my mom’s 2022 if I remember correctly, the owners manual recommends always charging to 100%. Because of this conflicting info from MINI/BMW I follow the general EV battery charging rule of 80-90%.
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Every now and then it's good for the Battery Management System (BMS) to charge to 100% to re-calibrate and balance the cells. Nobody really knows exactly how often but if MINI says you can go to 100%, then it's probably safe to do so.

SameGuy said:
I just realized the addition on (IIRC) page 238! I’d been using a pdf of the 2022 since I ordered my car, and hadn’t bothered with the Motorer’s Guide version once my app was unlocked upon delivery. I don’t see an ABC recommendation in the ’22 manual, but nowhere does it suggest the 100% and 10-80% that the ’23 book does. I’m inclined to believe it’s there as a CYA after the Bolt fiasco.
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I think Page 277 says "fully charged as possible" if you are planning on long term storage (3 months).
 
Here's an image I collected in the early days of getting my SE, not sure where I got it and it doesn't seem to correlate directly to the SE, but it's a good illustration of the buffering.

batterybuffers.webp
 
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