Notebook battery rebuild Lith-ion

**drand2** · December 24th, 2002, 01:33 PM

After finding repair info only in this forum, I decided to do some experimenting and will relate my experience here. My Hp 1739A Lith-ion battery gave out in about a year of little use. I found a used simular batt. on ebay (Dell) and took out a pair of good cells and replaced a pair of bad cells in mine. There is a circuit board inside of battery with wires going to each pair junction. I clipped the metal connectors with shears and did not try to solder connections because of all the warning about hazards with Lith-ion batteries. I taped mine together temporaryly and it started notebook but shut down before full boot up. I think it may need charging but didn't want to chance damage to computer till I return from planned trip to florida. I used a jack knife and small hammer and went along seam and tapped the knife blade to pop joint. Great care is needed here because of the circuit boards inside. I also made a shallow cut with razor blade with depth stop like a vise grip to prevent to deep cut. Here are links to pics of insides of batteries.
http://myweb.core.com/photos/drandall@voyager.net/Dell/
http://myweb.core.com/photos/drandal...er.net/laptop/ HP
I have some extra parts for Dell but I saw new ones for 3.50 on net the Sony US 18650 s

**Whir** · December 24th, 2002, 01:50 PM

How were you able to tell which cells were faulty?

Pretty neat little trick there.

Welcome to TechIMO.

**drand2** · December 24th, 2002, 03:39 PM

Well I measured each pair of voltage which were in the neighborhood of 3.9 volts. There are 4 pairs of batteries with spot welded strips joining each pair and in reality are seen as 4 cells. I read that lith-ion cells are all 3.7 volts just like all Ni-cads are 1.2 volts and metal-hydrides are another voltage. I found one pair that was 0 volts. I haven't yet checked to see if both were bad or one was taking out the other. Some where I read that when the lith-ion are discharged completly they are usually ruined? My batter HP 1739A has five terminals and the computer must use these for charging or testing. I just tried mine again and the computer fired up and when the screen read testing ??? it turned its self off again. THis happened yesterday also. I am not sure why but the two outside terminals on my battery show over 15 volts. the battery says 14.8 volts. Not sure whats making mine shut down.