Interesting article on battery life (BMWi3)

[ian4x4]

This article had some interesting observations on measured battery life, although its about a 3 year old, 70,000 mile, BMW i3.

http://www.bmwblog.com/2017/04/24/bmw-i3-long-term-battery-capacity-report-better-expected/

 

[pasquinade]

Nice read, thanks!

 

[elm70]

Well written article
10+ for English skills

But Very poor and misleading content

BMW lithium provided by Samsung lose in this single case only 4% in 3y and 70k miles

But each EV manufacturer use different Lithium batteries so what is good for BMW EV doesn't mean is good also for Nissan EV

For instance most of our PHEV lost already over 10% in less then 3y time

Finally what people has problem to understand with Lithium batteries is that ageing and degradation is not a function of km done, but is more a function how these are used

Leave 1y an unused lithium battery fully charged cause more damage then cycle it every day

Also something that most have problems to know / understand

There are two types of batteries degradation :
Capacity lost and increase of internal resistance

A battery that develops higher internal resistance can appear to have lost capacity only if fast discharged, for instance using such degradated battery in EV at low speed and low acceleration can even make same range as when was new

 

[elm70]

In short speaking of batteries and don't mention internal resistance when new and after x km or y years, and don't mention the real charging capacity from 3.7xVolt to 4.1xVolt at slow j1772 changing rate... Is just about speaking of unprecise and questionable estimation of real state of the battery

 

[pasquinade]

Hehe, It's a "broad audience" text, including "resistance" and "Volt" would be a shot in the foot

But I think it's great that these things are being discussed (even in everyday terms), it shows that it is an important consumer topic and manufacturers seem to be paying attention, raising potential consumers' awareness about what to expect with batteries (current and future directions).

I see a day when "changing battery pack" will be akin to changing tires (with different brands to choose from)... When this happens we'll arrive at similar dilemas of whether to put the cheap brand or the premium brand... and we currently do this without discussing tire chemical compositions or FEA analysis of thread patterns... In similar fashion, how many petrol car buyers actually know the difference between different octane levels at the gas pump? - No one cares about the technicalities, only about actual results (and in the case of octanes, a lot of myths).