Originally Posted by
Grim
Really I tried to keep this simple but here we are in a pissing match.
I don't think we've quite sunk to that level yet. This stuff is confusing, in large part because Li Ion batteries are different from NiCad and NiMH batteries, and some old "urban legends" are being applied to Li Ion batteries.
What should be stated clearly (and we don't disagree on) is that Li Ion batteries don't have memory issues, and that their primary enemies are heat and time. Not much we can do about time (except don't stockpile batteries), but plenty we can do to subject our batteries to as little heat as possible.
Originally Posted by
Grim
Batteries heat when charging.
If you look you should find charts showing that the amount of heat the battery is generating for a 30-70% charge is pretty flat but once you hit about 70% the internal temp of the battery starts raising because the internal resistance start raising as you approach a full charge. It starts to heat at an exponential rate and has to slow the charging to prevent overheating.
This is a very good point.
Originally Posted by
Grim
Back to the point or the argument that this has become: Why subject that battery to that heat daily when it has the capacity to go two days before it needs it?
Yes there is a thermo protection device in the battery that will shut down charging if the temp gets too high but still if you think of the logic "topping off" when that 70-100% part of the charge cycle is where the battery runs the hottest. So is the 40-100% charge habit every 2-3 days less detrimental or is the charge 75-100% every night? Thats the argument.
I think that if you know that the battery will last 2 days, then your approach is a good one. However, those of us who are on the road for longer still have a problem. (My commute is about 2:30 round trip).
In the absence of a good "fuel gauge" (and typical voltage monitoring isn't an adequate for these batteries, as it would be for Lead Acid batteries), there's no way to know if your battery will last another trip or not.
I suppose one other approach would be to have 2 batteries. Run on Battery A until the "shutdown point" and then swap to Battery B. Battery A goes on the charger and only returns to service when Battery B is fully discharged.
The problem here is that both Battery A and Battery B are "aging" simultaneously, and we're only using one of them at any given time. I'm not sure that any life extension from infrequent charging would be enough to be worth paying for 2 batteries.