[Tfug] Follow-up: Li-ion battery charging problem

[Rich]

Those (environ)mental hybrid cars and trucks don't let their  
batteries go above 70% or below 30% charge for this reason (I might  
have the figures wrong, but the principle's the same). That's how  
they can guarantee them for ten years. Laptop, cellphone, and other  
portable electronic thingy manufacturers don't have the same customer  
expectations, so they can classify them as "consumable items" and  
instruct you to allow the cells to discharge fully and charge fully  
on each cycle.
R.

On Mar 13, 2008, at 11:39 am, John Karns wrote:

> A few weeks ago I posted about a newly received replacement battery
> that I had deep-cycle discharged and that subsequently would not
> accept a charge.  The problem remained after stashing it in the fridge
> for several hours.  Ditto after a short heat treatment.  The idea was
> to jolt the chemistry.
>
> I tried again after leaving it alone for a week or so - no luck.  So I
> tried it again after about 3 weeks, and lo, and behold, the it
> accepted a charge.  I took two attempts, though - the first time I put
> it in the machine, the charge light came on, but then started flashing
> again after a second or two.  Pulled it out, and tried again - and it
> went to full charge.  Guess persistence pays.  I was glad I didn't
> just toss it out after having so many failures.
>
> My guess is that the temperature treatments were superfluous, but
> there is some voltage threshold that the internal voltage has to
> exceed before the cells will accept a charge, and leaving it set for
> an relatively extended period allowed the chemistry to bounce back
> enough to reach or exceed the threshold.
>
> Don't think I'll be deep discharging any rechargeable batteries again
> anytime soon.  Not intentionally, at least.
>
> -- 
> John
>
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