[NTLK] Successful DIY 2100 battery re-cell. with a couple ot tips.

Today I found the battery in my beater 2100 in "deepToast" state.
Nothing to lose by going for the rebuild now!
I cut along the factory seam with a small box cutter and care. I pried a little to see where I needed to cut deeper and eventually got the case split on the seam.

I took out the Toshiba cells and removed the current limiter, and negative plate, and positive plates from the ends of the cells with my pocket knife.
I set the dead cells aside for drop-off at the recycling center.

I used some Tenergy 2500mah cells with solder tabs already attached for the replacement cells. I was able to trim off some of the solder tabs on each unit.
First, I soldered the cells into 2 pairs.
TIP!
PLAN WHERE YOU WANT THE SOLDER TABS TO POINT WHEN YOU ARE DONE!

I suggest both tabs aimed at the positive side plate side of the pack. This will make putting the positive plate and the negative plate onto the ends of the pack easier.

TIP!
Keep either the + or the - end of the pack covered with a piece of electrical tape while you work and test fit things to prevent shorting out the battery pack.

With the plan to orient the solder tabs towards the positive side plate, I tinned and soldered on the current limiter.
Next, I cut off some of the original + side plate metal strip and more of the solder tab on the + side of the pack and soldered those together.
Finally, I put the negative end plate on the last cell. Yes, the tiny wire to the theristor broke off. I put that back on the plate, folded the negative end plate over and tested voltages.
voltage was >4 so things looked good.

I put the pack together without 2-sided taping the cells to the pack. I used a small amount of hot glue to secure the cells together. I also only glued the easy to cut sides of the pack back together and put the pack in the vice to harden. Less glue might make for easier re-work in the future.

It took a little sanding on the deep end of the pack to get it to fit well in my Newton. I didn't trim away on the curved end section enough after the cruel and sadistic case splitting procedure. Note to DIY'r. Take off a little more than you think when cleaning up the kerf.

Plugged it in. Newty reported fastCharging and 0% capacity.

Charge rate was 1.13amps or so.

The charge percentage calculation started at 0, went up to 67, then slowly dropped back down to 38% charged before it flipped to trickle charge. When it flipped to trickle, the capacity reported 100%.

Voltage went to 5.88 and stayed there as the temps finally came up when the cells got up to 100% I saw 5.87 for awhile, but I missed the delta for the cutoff to trickle. I think it is 3mv.

Battery temps came up as the cells hit max charge. Battery temp hit 47c with an ambient 30c.

Right now, the thing has been trickling for about 1 hour. It is about 1c above ambient. 5.5 volts.

No run time estimate yet. Sorry.

Good luck to any other DIY 2100 pack rebuilders. Frankly, it is a lot easier than a laptop battery pack rebuild!
-Stephen

  
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Received on Wed Jul 8 00:27:50 2009