Recommendations for battery charging

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Luis Abreu

Member
Hello guys.

I've just bought the new Cooper SE. I'm running about 50-60 kms per day and I live on an Island (with lots of ups and downs). I'll be charging it slowly from the wall socket (4 - 5 hours charging should be enough for my daily tasks), but haven't found any recommendations for extending the battery lifetime. I know that several people recommend keeping the batteries between 20 and 90% (I'm under the impression that Tesla recommends keeping it until 95%), but is there any official recommendation from the constructor? Is it ok to charge it every day until it reaches 90%? let's say battery level is 75%. Should I charge until it reaches 90%? 80%? Should I wait until it's lower before charging (going back to the 75% example, that is)?

Thanks
 
Luis Abreu said:
Hello guys.

I've just bought the new Cooper SE. I'm running about 50-60 kms per day and I live on an Island (with lots of ups and downs). I'll be charging it slowly from the wall socket (4 - 5 hours charging should be enough for my daily tasks), but haven't found any recommendations for extending the battery lifetime. I know that several people recommend keeping the batteries between 20 and 90% (I'm under the impression that Tesla recommends keeping it until 95%), but is there any official recommendation from the constructor? Is it ok to charge it every day until it reaches 90%? let's say battery level is 75%. Should I charge until it reaches 90%? 80%? Should I wait until it's lower before charging (going back to the 75% example, that is)?

Thanks
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Congrats on your new MINI Cooper SE! It seems it would be perfect for driving on an island (assuming electricity costs less than gasoline on your island).

The SE's Battery Management System (BMS) limits battery use to only 28.9 kWh of the battery's nominal 32.6 kWh. The unavailable 3.7 kWh is what the BMS reserves to prevent you from overcharging or completely exhausting the charge in the battery--two things that would definitely shorten battery life.

According to the EPA, 28.9 kWh is the equivalent of 0.86 gallons of gasoline. With such a limited capacity, MINI certainly expects people to fully charge the battery when they plug in.

Some manufacturers of battery-powered cars (eg. Honda) tell users to fully charge the battery because cell balancing takes place only after charging is complete. MINI probably didn't realize people might consistently stop charging early so they didn't address the cell-balancing issue. I'm pretty sure there is no way to balance the charge capacities of the various battery cells without fully charging the collection of battery cells.

The MINI Cooper SE manual says the way to stop charging prematurely is to unplug the charging cable. The only reason they suggest you would want to do that is to allow other devices to use that circuit:

upload_2020-6-5_13-50-37.webp

If MINI wanted to make it easy to charge to just 90%, they would have provided a programmable option to do that. My plan is to always fully charge the battery and hope that if it fails that failure occurs a few days before the warranty expires.
 
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Yeah, with no way to automatically reduce the charging end SoC I don't think it's worth worrying about. There don't be appear to be many issues with i3 batteries degrading and I believe the SE battery is identical to theirs. Does anyone know if the SE battery have the same 70%/8-year warranty as the i3?
 
Hello guys.

Thanks for the tips. I'll probably end up charging every day (or at least every two days).

Curious to see how's life with an eletric car
 
fizzit said:
Yeah, with no way to automatically reduce the charging end SoC I don't think it's worth worrying about. There don't be appear to be many issues with i3 batteries degrading and I believe the SE battery is identical to theirs. Does anyone know if the SE battery have the same 70%/8-year warranty as the i3?
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Electrek says the MINI Cooper SE's battery warranty is 8 years/100,000 miles for 70% of new capacity.

The slab-style Samsung battery used in the i3 wasn't workable for the MINI Cooper SE because BMW didn't want to raise up the whole car by a few inches to fit that battery underneath. Still, the MINI Cooper SE is 18 mm higher than it's MINI Cooper S gas-powered counterpart to protect the T-shaped, floor-mounted battery.

BMW went to battery-maker CATL to get more advanced batteries they could stuff into the former exhaust-system tunnel between the front seats and the space vacated by the gas tank under the rear seats. BMW says the MINI Cooper SE's batteries are less prone to cold-weather range-reduction than the i3 battery. I've speculated that the SE's battery packaging may make it easier to keep the battery warm, which would also help prevent cold-weather range-reduction.

You can see the battery in a cutaway MINI Cooper SE at the Plant Oxford factory in this video starting around the 1:30 mark.
upload_2020-6-6_10-15-50.webp
 
Hello again guys.

Just one more question: I've left the esve connected to the socket for about 6h30 hours (in order to achieve around 43% of battery back). I've noticed that the plug (that goes into the wall socket) was warm...is that normal? I was under the impression that it shouldn't get hot...

thanks guys.
 
I charged my Smart Electric on 12A x 120V single phase Canadian electric socket since 2013.
The original socket got hot, so I replaced it with a 20A capable upgraded socket that was more industrial grade, and that fixed the problem.
Heat is a sign of elevated resistance, it may be the contacts of the socket are not gripping the plug as well as needed.
I would absolutely check the socket and it's wiring.
Also ensure the socket is not shared with any other primary loads that would trip a circuit breaker.
 
Warm isn't terrible, but it shouldn't get hot no matter how long you leave it plugged in. Assuming the EVSE is good, you have to look at the socket. Is it old? Do you have another outlet at home or at a friend's house you could test to see if it, too, gets warm? Manufacturers warn not to use an extension cord.
 
Hello guys.

It seemed like only the plug from the esve (that goes into the socket) was warm. The socket itself wasn't (at least, I couldn't feel it). It is brand new and has been setup for the charging. It supports up to 16 amp (though the esve will only use 10). I'll probabl have to charge it today, so I'll keep a close eye on it.
 
I agree with you: it shouldn't get warm...I've asked the local support and they say it might get warm after a few hours. Their answer didn't really help I'm try to call the support line to see if anyone can get me a decent answer
 
After a couple of tests, it seems like the first thing that starts to get hot is the circuit breaker. Yesterday I've started monitoring the temperature of the circuit and I can report that after 3 hours of charging, the circuit breaker started to warm up while the other components were at normal temperature.

I'm thinking that (probably) the screws need to be tightened... after all, everything is brand new...
 
As I plan to use my Tesla's wall charger with my ordered SE, I'd like to know what scheduling of charging is possible with the Mini and/or its app.
Can you schedule start time? End time?
Can you set amperage?
I saw, above, that one cannot set the upper charging limit as one can with the Tesla. (We routinely charge to only 80% and have experienced very little degradation as a probable result.)
Are there printed instructions someone could point me too? I can't use the app until the car comes.
 
See the MINI Cooper SE Owner's Manual thread for a link to (and discussion of) the downloadable owner's manual PDF. The chapter on charging begins on page 216.

Via the on-board display, the car can be set up to begin charging immediately or charge for a scheduled departure time. With the latter, you can also specify a window of time with the lowest cost to charge (e.g. off-peak). Depending on the state of charge, it may begin charging outside that window if necessary to achieve full (or highest possible) charge by the scheduled departure time (including preconditioning). Up to 3 departure times can be set.

You can select 1 of 3 amperages for Level 1 charging only, and it's set to the lowest by default (likely to protect owners who haven't checked the capacity & load of the circuit they plug into). If you want to configure Level 2 charging current, that will have to be done on the EVSE. The car will tell the EVSE what current it needs, so it shouldn't be a problem if yours can provide more than it needs.
 
MichaelC said:
See the MINI Cooper SE Owner's Manual thread for a link to (and discussion of) the downloadable owner's manual PDF. The chapter on charging begins on page 216.

Via the on-board display, the car can be set up to begin charging immediately or charge for a scheduled departure time. With the latter, you can also specify a window of time with the lowest cost to charge (e.g. off-peak). Depending on the state of charge, it may begin charging outside that window if necessary to achieve full (or highest possible) charge by the scheduled departure time (including preconditioning). Up to 3 departure times can be set.

You can select 1 of 3 amperages for Level 1 charging only, and it's set to the lowest by default (likely to protect owners who haven't checked the capacity & load of the circuit they plug into). If you want to configure Level 2 charging current, that will have to be done on the EVSE. The car will tell the EVSE what current it needs, so it shouldn't be a problem if yours can provide more than it needs.
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Great info. Thanks for the reply!
 
Scott Altorfer said:
As I plan to use my Tesla's wall charger with my ordered SE
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I own two EV's, one uses J1772 and the other is a Tesla, the Tesla can charge in J1772, but my other EV cannot charge using the Tesla wall charger.
Tesla and Mini use different L1/L2 plugs. Mini uses J1772 whereas Tesla has a proprietary connector. Or did I misunderstand what you intend to do?

EDIT : I see another post of yours:
https://www.insideevsforum.com/community/index.php?threads/evse-recommendations.8985/#post-103528

You'll be using a converter to turn your Tesla charge cord into J1772 compatible, cool! Ignore my post.
 
SmartElectric said:
I own two EV's, one uses J1772 and the other is a Tesla, the Tesla can charge in J1772, but my other EV cannot charge using the Tesla wall charger.
Tesla and Mini use different L1/L2 plugs. Mini uses J1772 whereas Tesla has a proprietary connector. Or did I misunderstand what you intend to do?

EDIT : I see another post of yours:
https://www.insideevsforum.com/community/index.php?threads/evse-recommendations.8985/#post-103528

You'll be using a converter to turn your Tesla charge cord into J1772 compatible, cool! Ignore my post.
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For the money, the Tesla HPWC is very powerful, and its ability to daisy chain while load sharing makes it worth the extra price of the adapter. If it turns out my wife and I don't like tradinh/sharing, my plan is to buy and hard wire a second HPWC and mount it on the opposite wall, and then I'll back the Mini in.
 
I'm planning on having a level 2 charger (Siemens) installed for my future SE. Just curious if there are any chargers that DON'T work with the new SE or any advice I should consider. Thanks in advance.
 
GDOG said:
I'm planning on having a level 2 charger (Siemens) installed for my future SE. Just curious if there are any chargers that DON'T work with the new SE or any advice I should consider. Thanks in advance.
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Cant think of any that aren't compatible... Tesla would not work for obvious reasons. Get something that can output at least 32A on a 40A breaker.
 
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