Laptop Battery Rebuild - Partial Succes, laptop shuts down even if battery is still charged

[juve145]

Hello. I have an 12-14 year old laptop laying around, and I decided to rebuild it's bettery (like here)

At first, I thought the whole thing was a succes, as the old battery was completely dead, and after I have replaced the cells (with some other cells from a used battery, but still functional), the laptop was running on battery!

Buuut, it didn't last long... The laptop lasts on battery for about 2 minutes. (The battery had initially 8 cells, 4 sets, each consisting of 2 batteries connected in paralel, and I have put only 4 batteries, which should reduce battery life, but not as much)

The problem is that even after the laptop shuts down, when I mesaure the voltage of each cell, it still has about 3.9-4.0 V, which means they are not even close from beying empty. My question is then... why my laptop stops? Is it related to the battery firmware? I have tried recalibrating the battery with some software outside windows (pressing F6 when computer starts brings me up smart battery auto learning). After some recalibrations with that... now it shows that my battery has negative capacity (at first it pointed 190 mAh, then -500 mAh, then -800mAh, and now -1000 mAh, while the battery had 4400 when it was new)

Also, If I disconnect the battery from the laptop and connect it again, the laptop runs for aboout 30 sec, then it shuts down. I can do this several times, with the same result.

Any ideeas on how I can deal with this?

 

[ElectrO_90]

Voltage is not a measure of how good the batteries are, because they can show being high, but underload is when you have to measure voltage.
Also the reason most battery packs die, is because only 1 cell dies a death. Have you checked all cells? They can be checked with voltage because they would be under the 1.2/3.6v whatever the rating is you are using.

Voltage is extremely important when it comes to Electronics, but ampage for longevity. If its 12v and 1 cell is down, then that alone just stops things working well.

 

[juve145]

I have checked the voltage of all cells, they are all about 3.9V, and they last about 3 more hours while connected to a led and a 21 ohm resistor (the led and the resistor are connected in paralel, and I did that after the laptop stopped working, without recharging the batteries) so I assume they are still about half of they're factory capacity.

 

[ElectrO_90]

Maybe the sensing circuit has got damaged some how.
It does seem a bit of a mystery, the only true way is to find someone with exact same original battery and see what happens then. Otherwise its going to be a fun fault finding mission.

 

[jarotech]

Hi, it's a risky adventure, you have on the motherboard of the battery a chip with the information on the cells, if you change the cells to new cells, this chip will not be aware of the new cells. This chip will need to be reprogrammed for the new cells to work. If you follow the instructions of the site you are referring to, this guy does not know what is related to the cells in the battery.