Limiting max charge level (tip)

A

AndysComputer

Well-Known Member
As we know, Mini don’t allow us to set a max charge level cutoff, it keeps going until it hits 100%. For cars that get used daily I don’t think it much matters, and I imagine BMW added enough top buffer that it isn’t really 100% anyway but…
As our Mini isn’t used daily and I wanted to keep things as simple as I can for my wife I have been doing the following to limit the car to 90% without having to monitor it and unplug.

Our EVSE is a smart one which provides a couple of features that mean we can pull off a charge limit due to our usage profile.

Essentially I tell my wife to only plug in when she gets home if the car is below 50% charge. This takes a few trips for her.
I have a 15kWh session limit set on the EVSE. So it cuts off after 15kWh is delivered which adds about 50% and thus takes the car up to about 90% allowing for charging losses at which point it switches off.
She typically plugs in at just under 50%, so it works well.
The EVSE also offers a session time limit so a quick bit of math on charge rate and time would achieve the same thing.
If we used the car a lot such that we got home on say 20% (this is a once every few months type thing) it would only charge up to 60% before cutting off. That’s fine as over the next day or two she’s use it and it would drop below 50 causing her to plug it in again and it would hit 90.
This technique might work for a few ppl on here who are light users and would like to avoid keeping the car at 100%. Just adjust the session limit to whatever you’re comfortable with for your use case. Assuming your EVSE has such a feature obviously…
 
Good suggestion. I am using a 16 amp dumb EVSE, and I noticed that I will get about 10-11% charged for every hour it is plugged in. So my even simpler approach is to set a timer on my phone to remind me to unplug it. For example, if I plug it in at 50%, I set a timer for 3 hours.
 
is there any proven data that shows that charging to 100% does any significant degradation to the battery?

i feel like the hassle of charging to 90% is not worth the actual loss that you get by just charging all the way
 
xd366 said:
is there any proven data that shows that charging to 100% does any significant degradation to the battery?

i feel like the hassle of charging to 90% is not worth the actual loss that you get by just charging all the way
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All battery chemistries are affected by charging to 100% bar the LiFePho type which is not what is in the SE.
The way around the problem if not limiting battery charge is to have additional top buffer do that 100% full is not really 100% full. GM did this on the Volt to good effect. I suspect this is what BMW have done so limiting charge isn’t necessary.
As for whether or not it’s worth doing so anyway depends on your use case. Charging to 100%, it takes a week for my wife to get the battery down under 60%. Equally, if she then plugs it in and charges to 100% it may then site at 100% for a couple of days before she uses it. Given I can limit the charge to 90% using my method with no hassle and she has no need for all the range the Mini has to offer, why wouldn’t I do it?
 
IIRC the autel EVSE you can set the timer and charge % through the app from what I understood from the Autel rep
 
The cars do not communicate their charge level to the EVSE as their onboard charger is handling the process. So that sounds technically impossible to me.
On DC fast chargers the onboard charger is bypassed and the third sorry charger knows the battery level.
 
That’s what I think he was confused on.
That being said Mini can add charge % easily via software update. It is really puzzling why they didn’t. I’d laugh if the function is buried but just not activated
 
MrSnrub said:
That being said Mini can add charge % easily via software update. It is really puzzling why they didn’t. I’d laugh if the function is buried but just not activated
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I take this as another datapoint that MINI chose the KISS (keep it simple, stupid) approach by putting in a big enough top buffer that charging to 100% SoC would not risk damaging the battery. How can MINI expect owners to limit the charge % without providing a means to manage it? That seems like a nice way to risk lawsuits.

Anyone know what BMW guidance on their EV models happens to be?
 
Puppethead said:
I take this as another datapoint that MINI chose the KISS (keep it simple, stupid) approach by putting in a big enough top buffer that charging to 100% SoC would not risk damaging the battery. How can MINI expect owners to limit the charge % without providing a means to manage it? That seems like a nice way to risk lawsuits.

Anyone know what BMW guidance on their EV models happens to be?
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80% for I4 IMG_9349.webp
 
When Grizzl-E launched their new Mini model with “smart” features, they said the local web interface would be available in an upcoming update for the wifi-capable Grizzl-E Smart EVSE, relegating the nearly useless ChargeLab app to the dustbin. I’m still waiting.

IMG_1428.webp

IMG_1429.webp
 
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If I’m down to 30%, I know I’ve used about 20 kWh. I can set a limit of 15 kWh to get back to the comfort zone. That’s all I really need. Math is easy with this car.
 
MrSnrub said:
80% for I4
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Does BMW software allow one to set the max SoC % for shutting off charging? I know the SE manual originally said charge to 100%, but the newer version says something similar to the BMW manual, which I personally believe was just a cut & paste modification not grounded in any facts.
 
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