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Discussion Starter · #1 ·
Knowing that, lithium-Ion batteries are not designed for extremely low nor high temperatures, on the other hand there are also claims that Fast chargers are entirely beneficial when the state of charge (SOC) of Li-ion battery remains within 30-80% range, and the battery temperature remains between 0-30° C.

Does this concluded that when the battery is fully depleted and it is freezing, you should use an 11Kw charger....and fast charges should only be used when all conditions are met:
  • SOC 30-80%
  • Temp 0-30°C
  • Max once every 24h
 

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30-80% range for fast charging is because = fast current range
the battery manages its temperature
no time constraints between two charges

=>use fast chargers when you need them, normal charge otherwise

what destroys the battery the most is the circulation of a high current, in charge as in discharge
 

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9 months and 13000kms into our VW ID4 ownership and have only had to use a public charger once, I’m hoping that trend continues with the i4.
 

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I don’t do it, but I’ve seen guys using fast chargers 90% of the time for their charging needs with no issues. They usually charge to only 80% though. I’m not sure if this negatively impacts range (capacity) over the long term. I’ve read different theories, but my gut reaction is it’s not the best approach
 

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All my charging will be done at public chargers. Will be using fast charging a lot, and in normal daily driving I think I will limit my charging to 80%.

Living in a city, I will mostly be driving on city streets, so hopefully I will not need to charge very often due to the long range when driving at 50-70 km/h. So i'm not afraid I will damage the battery.
 

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According to the genius, the i4 cannot make use of faster charging than 11.5kw on a level 2.
So That is what I will be looking to set up in my home.

Dan
 

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I wanted to post a similar question a few times before.
My friend @Inside will charge his i4 up to 80%.
What that means exactly?
The "battery" consists of many cells.
All the cells will be charged to 80% or 80% of cells will be fully charged or something between?

This of course has everything to do with the life of the battery too.
 

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I wanted to post a similar question a few times before.
My friend @Inside will charge his i4 up to 80%.
What that means exactly?
The "battery" consists of many cells.
All the cells will be charged to 80% or 80% of cells will be fully charged or something between?

This of course has everything to do with the life of the battery too.
I only know the manual suggest to charge to 80%, that's why I will try to keep it at that. But will charge to 100% when I need the range.

How it technically work I would also like to know. Hope somebody can answer how the cells are charged when set to 80%
 

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Discussion Starter · #11 ·
I only know the manual suggest to charge to 80%, that's why I will try to keep it at that. But will charge to 100% when I need the range.

How it technically work I would also like to know. Hope somebody can answer how the cells are charged when set to 80%
I'm no expert but i understood that the BMS (Battery Management System) can calculate the state of charge based on the individual voltage of a cell. ex 3.7V fully charged, 3.5V 1/2 charge, 3.0V empty...the actual numbers will depend on the chemistry of the battery.
ALL cells will have the same charge, always....if not the BMS will try to balance the charge till all are equally charged.
 

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According to the genius, the i4 cannot make use of faster charging than 11.5kw on a level 2.
So That is what I will be looking to set up in my home.

Dan
Just use whatever is available around your garage. If there is a dryer plug or electric range plug nearby then use it. High power EVSE is nice, but running the wiring can be expensive. If you need to top up in a hurry, then go to public DCFC.
 

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This actually piques my curiosity; @aigarius and @Mycroft, please keep me straight.

So BMW says they have 4 modules of 72 battery cells and 3 modules of 12 cells, and each module is 3.7V because that's dictated by the Lithium-Ion chemistry. So to make a 400V battery, they have to connect 2 of the modules of 72 cells (cells would be in series inside 72 x 3.7 = 266V) in series with half of the cells of a 3rd module (36 additional cells x 3.7 = 133V, total 399V); and then, the 4th and last 72-cell module would be connected in series with the 3 modules of 12 cells, all in series, 266V + 3 x 44.4V = 399 V. So their BMS basically has to keep the resulting 4 strings of 72+36 = 108 batteries each, in balance. When you charge a string of batteries in series, the same current flows through all of them so in principle the charge should be equal in them.

This being said, the manual does recommend to minimize DC charging and use AC charging (up to 11kW) as much as you can, but stop charging at 80% SOC most of the time - they do say you CAN charge to 100% ahead of long trips where you might need the full range without impact to the longevity of the battery pack. So that's what I plan to do, AC charging to 80% every night at home, bring it up to 100% in preparation for long trips, and DC charge on the road as necessary. And on road trips, I do plan using destination chargers (AC) whenever overnighting. Very different approach and discipline compared to filling up an ICE car.
 

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Does anybody know whether, say, 80% SOC is based on the maximum raw capacity of the battery pack, 83.9 kWh, or the usable capacity, 80.7 kWh in Europe and 81.5 kWh in the US? (and why the difference?)
 

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I would guess the usable capacity since that’s all the user ever sees. The maximum capacity is always hidden.
 

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Do not worry about using your car. It has been designed by clever engineers with all the provisions and safety features so that you can just use it as you need it without any significant issues. Fast charge as often as you need and as fast as you can, even up to 100%. It will not "hurt the battery". Use it down to 5% freely. It will not "hurt the battery". Leave it charging for days, it is not a problem. There is a Battery Management System in the car whose job is to worry about such things, so you don't have to. It would be really, really hard to actually do damage to a i4 battery even if you actually wanted to. Not by normal usage, for sure. Unless you are opening the battery casings up and shorting wires. It's not a phone or laptop - there is far, far more smarts build into the BMS to make the battery last and perform for years and years.
 

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Do not worry about using your car. It has been designed by clever engineers with all the provisions and safety features so that you can just use it as you need it without any significant issues. Fast charge as often as you need and as fast as you can, even up to 100%. It will not "hurt the battery". Use it down to 5% freely. It will not "hurt the battery". Leave it charging for days, it is not a problem. There is a Battery Management System in the car whose job is to worry about such things, so you don't have to. It would be really, really hard to actually do damage to a i4 battery even if you actually wanted to. Not by normal usage, for sure. Unless you are opening the battery casings up and shorting wires. It's not a phone or laptop - there is far, far more smarts build into the BMS to make the battery last and perform for years and years.
So there is a difference between doing harm and having an impact on capacity and longevity. There must be some reason why manufacturers, including BMW, say don’t make a habit of charging to 100% except for long trips. There must also be a reason why almost everything you read regarding charging says don’t make a habit of high speed charging.

I’d love to believe that none of this special care is necessary, but I’d also like to see the documentation that details why that’s the case.
 
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