Thinkpads Forum

Just in case anyone is curious,

I ripped apart my crappiest 9 cell battery today.

Thought i would show some photos of it in case anyone is interested.

It was quite difficult to separate the case halves. I don't think many people could separate them and they remain useful. I considered rebuilding it, but it's probably not worth the effort. It is VERY easy to get a short pulling this apart. The connection tabs edges are sharp and cut through the cell cases very easy. I had a short and I was very careful with this process.

Enjoy.
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The 9 cell is just 3 sets of 3 batteries in parallel. Monitored between each cell group. A single thermister/thermocouple monitors one battery. They appear to be 18650 cells. The labels are not real legible. This was a Sanyo pack. It only had 340 cycles on it and was down to 19% capacity. I could basically drain it in 15 minutes. Useful only for moving between power packs or docks.

Interesting, thank you. I know, sometime in the future, I will need to recycle my batteries.

I have actually removed the cells from a couple of my old non-functional batteries and put the plastic case back together again as a 'dummy' case. I always remove the battery from my Thinkpads if I work on ac power for a longer period of time, so I mainly use a battery when I know I will be moving around a lot, and when I travel. The need for a 'dummy' pack came when I used my old T30. The T30 was wiggling without the battery installed, as one of the laptop's rubber feet was a part of the battery casing. So I when I took the working battery out, I put the empty 'dummy' case back in to have the laptop sit properly on my desk.

I have also made these dummy batteries for my T4x and T6x machines. Even though they sit properly even without the battery installed, it is easier to grab and handle it with the plastic battery casing is there. And the laptop looks a little bit more complete.

I think it cannot be done

I tried some time ago to re-cell a T40-battery, only to find out that when re-assembled it would not accept any charge. It seems, that the circuitry in the battery holds history of the cells, and when that has been taken off battery voltage it will need to be reset. And at the time that was not possible.

It can be done, but you must keep all battery cells connected at all times to the battery's electronics!
You first solder 1 new cell in, parallel to the old one, and only after the new one is soldered in do you remove the old cell!
Repeat for all cells.

RBS, electrically, each bank of cells are in parallel. There's no individual monitoring of cells. So functionally, the charge circuit couldn't determine if a cell had been removed unless there was a drastic change in voltage with one removed. I didn't measure a big difference in voltage between any of my cells. I've removed them all now and will let them sit for a while to see.

So basically a made up pack with some jumper alligator clips could function as keep-alive memory.

On the charging issue,

I saw one gent on youtube "jump start" the charge circuit on a thinkpad battery by jumpering from the battery cell directly to the + terminal on the OUTPUT of the battery to the laptop.
At that point, the battery came alive and stayed active. Perhaps there's no power supplied to start the circuit unless it comes from an external path to the circuit?

It's my intention to try this at some point. At this point, i have nothing to really lose. the battery was pretty much useless.

There's no one right answer because different brands of batteries behave differently. Some batteries will deactivate forever if the cells fail. Some will work with new cells. I've had bad luck rebuilding Sanyo batteries because the controller won't learn the new charge capacity (it actually decreases on each cycle). I did successfully rebuild a Sony T60 battery in the Thinkpad I'm posting from. It had no trouble learning the new full charge capacity (it took quite a few cycles for it to get there).

If the cells discharge much below 3v per cell, the control circuit will prevent the battery from charging. This is often a problem on batteries that haven't been used for a long time. It's often possible to jump start these batteries, but it depend on the controller. I use a current limited power supply to charge them above 3v per cell and then see if it will charge.