tomkovic said:
The battery has highest internal resistance at the high and low ends of state of charge so it's more efficient and less taxing of the battery to not charge to 100 %. But what if your battery has lost a bar of capacity? Charging to 80% of original capacity may now be 90% of present capacity. So once you've lost a couple bars a 100% charge is now 80% of original capacity. So in that case does it matter in terms of battery life if you charge to 100%?
Sorry if this is an old issue. I couldn't find it anywhere.
Your wording of this question is a little confusing, but yes, it still matters. The charging bars always represent a percentage of the CURRENT capacity, not original capacity, so charging to 100% even though battery capacity is at 80% is still a "deep" cycle.
These issues has been discussed at length here. The fact that you couldn't find it anywhere just reflects on the difficulty of searching this forum. Using the Google custom search bar usually returns better results.
The consensus seems to be that charging to 100% is less of a factor in battery life than heat and calendar aging. Put another way, it appears that both calendar capacity loss and cycling capacity loss are temperature dependent, with climate being a large contributing factor in both. Some people have charged to 100% every single day in cool climates (PacNW) and suffered much less capacity degradation than others in hot climates who have babied their battery pack by only charging to 80% religiously (AZ, TX, FL). I suggest you peruse the battery capacity wiki rather than search the forums:
http://www.electricvehiclewiki.com/?title=Battery_Capacity_Loss
The bottom-line reality is that as you lose battery capacity, it becomes a necessity to charge to 100% more often (and perhaps QC more) in order to maintain the same functionality of the vehicle, which will indeed hasten further degradation, but the degradation curve is also flattening out somewhat at that time, so the effect may be diminished compared to when the battery was new. In the bigger picture, it seems where you live has the most to do with how quickly your battery degrades. I don't see your location in your profile--adding it may help people answer your questions in the future.
TT
