[ltp] T42p + Battery Rundown and results

[David A. Desrosiers]

> On Sat, 16 Feb 2008, David A. Desrosiers wrote:
>> design capacity:         71280 mWh
>> last full capacity:      25450 mWh

> Bad...

I agree :)

> You don't need any windows utility to do this, the battery 
> eletronics themselves take care of it, and tp-smapi can be used to 
> force which battery to discharge, if you need to do that.

I use the PC Doctor bootable ISO to do this, which eliminates the OS 
and the primary HDD from being involved in the process. I actually 
liked using the floppy version because it worked *MUCH* faster. 
Apparently the floppy drive heads themselves took a lot more power to 
actuate.

> Li-ION cell refresh is a lot more difficult, and AFAIK the best you 
> can do without special hardware and fire hazard safety is to let it 
> charge to full, then discharge it *very slowly* to zero (e.g. leave 
> the thinkpad sleeping until it depletes the battery), then charge 
> again to full (to also reset the gague while at it).  Do it at 
> 20C-25C.

I can't go 4 weeks at a time without my laptop, sorry. That's not 
really a viable option.

Does anyone make a "desktop charger" similar to this, but for IBM 
batteries?

http://www.mahaenergy.com/store/viewItem.asp?idProduct=423

Basically the "deep discharge", "refresh" and "cycle" capabilities. It 
would allow me to charge the batteries while NOT disabling my ability 
to use the laptop with an AC adapter or other battery in it.

> If your batteries are more than 2 years old, and you have NOT kept 
> them most of this time stored at about 40% charge @ 10C, they're 
> just old.  Don't mess too much with them, you'll just damage them 
> further.  Do a gauge reset every 20 cycles or so, and start saving 
> $$$ to get a new pack :p

These batteries *NEVER* held more than maybe 1.5-2 hours of battery 
life, max. I bought them both new from IBM when I bought the laptop, 
because I knew I'd need a lot of battery life/power on my flights and 
travels.

After about 1 year, they both dropped their capacity by about 50%. I 
took great pains to make sure the batteries were charged/discharged 
properly and that they were stored carefeully.

I did *NOT* however, store them at 40% charge, because that renders 
the whole point of a second battery useless, when I can only get 15-20 
minutes out of it at 40% charge.

> Other than replacing the cells, which you are better off NOT doing 
> in the first place?  AFAIK all you can do is to get a new battery 
> pack.

It's a 6,600mAh pack, but when I Google the FRU, I get a lot of places 
making what appears to be "compatible" battery packs, but they're not 
IBM or Lenovo packs.

What is the liklihood that these "aftermarket" battery packs are of 
the same quality and capacity as the original IBM units? The price 
difference is shockingly different between the two.