What's bad for our batteries?

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vger105

Active member
Joined
Jan 26, 2020
Messages
27
In addition to excessive heat and excessive cold, are there other things that are harmful to our i3 batteries?
 
Allowing the battery pack to remain at a very high or very low charge level for an extended period of time. Even though the i3's battery management system (BMS) prevents the battery pack from being charged to its actual full charge or to be completely discharged, battery cell degradation accelerates as the charge level increases or decreases from a mid charge level range (i.e., 40% - 60%).
 
Depending on who you ask...

Fast charging (DC or 32A Level2)
Discharging to 0%
Charging to 100%
Long-term parking
Charging too frequently
High number of discharge cycles
Charging when hot
Charging when cold
Looking at your car in the wrong way :lol:

My $0.02 is to let the battery management system do the worrying and just enjoy your car, trusting that the BMW engineers have picked the best set of tradeoffs to ensure a long and productive vehicle life.....
 
Most of my charging (2016 94Ah REX) over the 26 months I've had my i3 has been done with 50kW rapids, as I mainly use the car for long trips (rarely under 100 miles...)

I've not noticed any significant loss of capacity, but if this happens I want it to do so before the battery's warranty expires (so BMW picks up the tab...)

So I'm not planning to change this strategy, as eventually I want to replace the original battery with a higher capacity unit (120Ah+?)


Chris
 
Busfolder said:
Most of my charging (2016 94Ah REX) over the 26 months I've had my i3 has been done with 50kW rapids, as I mainly use the car for long trips (rarely under 100 miles...)

I've not noticed any significant loss of capacity, but if this happens I want it to do so before the battery's warranty expires (so BMW picks up the tab...)

So I'm not planning to change this strategy, as eventually I want to replace the original battery with a higher capacity unit (120Ah+?)


Chris

How do you have a 2016 94aH? :?

I haven't yet seen anyone post significant degradation on a 94aH car (could just be because they don't have enough miles yet). Makes me wonder (hope) if the battery chemistry is more resistant to it.... or it might just be that the same distance traveled with the 60aH car is 1.5x as many battery cycles as the 94aH car...
 
[How do you have a 2016 94aH? :?/quote]

I bought it used (at 8300 miles in its first year) in late December 2017, so I guess it was an early UK 94Ah car.

Just passed 28000 enjoyable and economical miles (by careful choice of public chargers- UK pricing varies wildly!)

Have recently installed the BMW Connected app, and much appreciating the remote preconditioning capability!

Chris
 
Busfolder said:
I bought it used (at 8300 miles in its first year) in late December 2017, so I guess it was an early UK 94Ah car.
Apparently in Europe, the model year of a car is the year in which it was built. If an i3 built in late 2016 were classified as a 2017 model in the U.S. (e.g., a 94 Ah i3), it would be a 2016 model in Europe.
 
vreihen said:
Depending on who you ask...

Fast charging (DC or 32A Level2)
Discharging to 0%
Charging to 100%
Long-term parking
Charging too frequently
High number of discharge cycles
Charging when hot
Charging when cold
Looking at your car in the wrong way :lol:

My $0.02 is to let the battery management system do the worrying and just enjoy your car, trusting that the BMW engineers have picked the best set of tradeoffs to ensure a long and productive vehicle life.....

Yes, most of these things aren't good for the battery and we should hope the battery management system does a good job. That said, what would be the best practices? Would be good to know the order in which these things are best/worse for the car. I'm thinking discharge to 0 is very bad and charging frequency based on cell phones.
 
panamamike said:
...what would be the best practices? ... discharge to 0 is very bad and charging frequency

It's not possible to drive the i3 to zero. It holds a substantial reserve. Zero indicated is virtual. Same at 100%.

Frequency of charging is said to have no effect on battery health. One hundred 10% charges has the same degradation as ten 100% charges. Leaving it plugged in won't overcharge it.

The most impactful degradation seems to be frequent DC fast charging.
 
eNate said:
panamamike said:
...what would be the best practices? ... discharge to 0 is very bad and charging frequency

It's not possible to drive the i3 to zero. It holds a substantial reserve. Zero indicated is virtual. Same at 100%.

Frequency of charging is said to have no effect on battery health. One hundred 10% charges has the same degradation as ten 100% charges. Leaving it plugged in won't overcharge it.

The most impactful degradation seems to be frequent DC fast charging.

That's good to know. Too bad DC fast charging is a negative. I suppose the next worst thing is not pre-conditioning the battery? Meaning if it's very cold or hot it's beneficial to precondition vs. using the battery at the extreme temps.
 
panamamike said:
eNate said:
panamamike said:
...what would be the best practices? ... discharge to 0 is very bad and charging frequency

It's not possible to drive the i3 to zero. It holds a substantial reserve. Zero indicated is virtual. Same at 100%.

Frequency of charging is said to have no effect on battery health. One hundred 10% charges has the same degradation as ten 100% charges. Leaving it plugged in won't overcharge it.

The most impactful degradation seems to be frequent DC fast charging.

That's good to know. Too bad DC fast charging is a negative. I suppose the next worst thing is not pre-conditioning the battery? Meaning if it's very cold or hot it's beneficial to precondition vs. using the battery at the extreme temps. I say this because different people have experienced different levels of battery degradation. Seems those in the more extreme climates, hot or cold suffer more capacity loss.
 
panamamike said:
I suppose the next worst thing is not pre-conditioning the battery? Meaning if it's very cold or hot it's beneficial to precondition vs. using the battery at the extreme temps.


I don't **think** so.

A battery is most efficient when it's warm, it's going to get hotter than ambient under use, and cold temps make make it less efficient in the here and now, but I don't believe has any impact to longevity.our overall health
 
eNate said:
panamamike said:
I suppose the next worst thing is not pre-conditioning the battery? Meaning if it's very cold or hot it's beneficial to precondition vs. using the battery at the extreme temps.


I don't **think** so.

A battery is most efficient when it's warm, it's going to get hotter than ambient under use, and cold temps make make it less efficient in the here and now, but I don't believe has any impact to longevity.our overall health

Then why have a battery pre-conditioning function?
 
The battery is more efficient when it's up to temperature, so a warm battery will provide more power / range for a given state of charge. But I don't believe it harms the battery to use it cold.
 
Is there a proven disadvantage of charging it daily to 100% (AC)?
If I insist to avoid it I could program my departure time to say 30min after my actual departure, thus charge the battery to around 90% full. I don't need the extra range but does it worth to do at all?
I have the 120Ah.
 
Is there a proven disadvantage of charging it daily to 100% (AC)?

Impossible to do. When you charge to '100%', you are actually only charging the battery to 92% - 95% because of buffer space BMW has set for the HV battery to protect it (so you don't have to).
 
vreihen said:
Depending on who you ask...

Fast charging (DC or 32A Level2)
Discharging to 0%
Charging to 100%
Long-term parking
Charging too frequently
High number of discharge cycles
Charging when hot
Charging when cold
Looking at your car in the wrong way :lol:

My $0.02 is to let the battery management system do the worrying and just enjoy your car, trusting that the BMW engineers have picked the best set of tradeoffs to ensure a long and productive vehicle life.....

:lol: :lol: :lol: Indeed...life's way too short to sit there and worry about my car's battery pack. I don't plan on keeping it forever and lease most of my cars anyway so such issues are absolutely no concern to me.
 
Arm said:
Indeed...life's way too short to sit there and worry about my car's battery pack. I don't plan on keeping it forever and lease most of my cars anyway so such issues are absolutely no concern to me.



Lol. Those are my wife's exact sentiments about my i3. Of course, she hadn't joined any i3 forums so won't be here to share her lack of opinion about it.
 
I noticed somebody lumped 32a level 2 charging in with DCFC as possibly harmful. Is there an actual consensus on this? I just bought a 2014 Rex, and while I don't plan to obsess over battery life, I'd obviously like it to last as long as possible. I installed a 32a charger at home because I do almost 40 miles on most days and more than that on some, so I wanted to ensure I'd have full juice everyday. With the battery buffer and BMS, I figured that was a non-issue. Incorrect?
 
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