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Re: Charging to 80% capacity

Posted: Wed Jun 22, 2022 12:38 pm
by eNate
I recall reading fairly convincing proof (from the archives, here in this forum) cell balancing occurs at lower states of charge.

But because balancing relies on voltage, it's most effective at high SOCs where there's a meaningful difference between hundredths of a point, where for mid SOCs it's pretty flat.

Re: Charging to 80% capacity

Posted: Thu Jun 23, 2022 10:56 am
by alex29a
I constantly keep my ( now 37000 miles ) 94Ah ( Rex ) Charged up to 100% using the slow home 10A granny charger
as soon as I have used 30-40 miles and the % falls to around 68-70% , it's on charge for around 4-5 hours

I am happy with that, having peace of mind full range.
So far the battery behaviour has been consistant on all the usage/charge readings.
showing no sign of degradation.

I have also left it sitting 100% fully charged for 15 Days when was on holiday.
No effect on anything

Perhaps ?? is it becase a slow charge has less harmful effect on the battery
than fast charge ..? if anyone can comment of that

Re: Charging to 80% capacity

Posted: Thu Jun 23, 2022 4:21 pm
by alohart
alex29a wrote: Thu Jun 23, 2022 10:56 amSo far the battery behaviour has been consistant on all the usage/charge readings. showing no sign of degradation.
Noticing mild degradation can be difficult. The free mi3 app (iOS) or electrified app (Android) reports the battery pack state of health which is probably a better indication of degradation than trying to associate usable battery capacity with range that fluctuates with temperature, driving conditions, tire inflation pressure, and several other factors.
alex29a wrote: Thu Jun 23, 2022 10:56 amI have also left it sitting 100% fully charged for 15 Days when was on holiday. No effect on anything
Maybe, maybe not. 15 days isn't terribly long, but the effects could take a while to be noticeable. BMW warns about leaving the charge level too low, but doing so would likely not be immediately noticeable. Degradation occurs slowly over time, so for those who want to minimize degradation, it's best to avoid doing things that experts advise against.
alex29a wrote: Thu Jun 23, 2022 10:56 amPerhaps ?? is it becase a slow charge has less harmful effect on the battery
than fast charge ..? if anyone can comment of that
1 C is the charging power that would charge a battery pack from 0% to 100% in 1 hour. 240 VAC Level 2 charging at 30 A (7.2 kW) isn't fast (only 0.22 C for your 33 kWh battery pack). It's probably no worse than 120 VAC Level 1 charging at 10 A (1.2 kW or 0.04 C). DC fast charging (50 kW or 1.5 C) might be more harmful than AC Levels 1 or 2 charging, but those who have looked for evidence of this haven't found much. Other EV's charge at C rates greater than the i3 yet don't suffer much battery cell degradation. If one charged only using DC fast chargers, degradation might be greater over several years than had one charged at AC Levels 1 or 2.