Does anyone have any info about recelling old laptop batteries?

[Caleb Hansberry]

Is there anything anyone can tell me about recelling this battery? Its from a ~1997 Dell XPi CD laptop. When it's in the laptop it never passes 0%. It has a very large circuit in it and there are two buttons - I'm curious why, as one reports the amount of power on a few LEDs, but I dont know what the other one does.

Is this even possible to recell or will the circuit ban me from doing so?

 

[GiGaBiTe]

Some batteries are smart and record the number of charge/discharge cycles, as well as the state of each bank of batteries and will brick itself after it deems the pack is expired. Others have monitoring circuitry but don't brick themselves when the batteries start failing, these can be re-celled.

The only way to know which is which is to see if anyone else has run into the issue or attempt it yourself. I've re-celled a few battery packs with mixed results, but have not yet run into a self-bricking battery pack.

When buying replacement 18650s, make sure you don't get garbage cells with fake ratings (ie. ultrafire with their 6000-9000 MAh ratings.)

 

[ChrisUnionNJ]

And don't buy ebay cells I use 18650's from
IMR batteries for my vaping needs but
there not just for vaping..

 

[Caleb Hansberry]

Alright, I'll be sure to buy only high quality cells. I guess I'll buy some cells and try it out, hope it works, when I get the money. I'm still dying to know what the second button does though.

 

[GiGaBiTe]

You can buy rotgut cheap cells if you want to test if its worth it to use high quality cells. A good source for cheap 18650s would be to just buy a battery pack for a newer model laptop and tear it apart. Though it looks like your pack has 8 cells, so you'd have to get a couple of 6 cell packs.

Alternatively, you could pull the existing cells out and see if any of them are still good and weed out the dead ones so you only have to replace a few cells for testing.

 

[Caleb Hansberry]

How do I test a cell? I'm guessing it wont have any voltage and dont know how to charge one.

 

[GiGaBiTe]

Get the cells apart individually and test their voltage. A fully charged cell should be 4.2v, and settle down to 3.7v after some use.

If you have any cells that measure a reverse charge, they're damaged and should be tossed. If any of the cells have a very low charge, you can try and recover them, but you'll need a current or voltage limiting supply.

For a current limited supply, set the voltage to 3.7v and a current limit of 50-100mA and try charging the battery. If the voltage does not steadily rise, or if the voltage on the battery quickly falls off when the supply is removed, the battery is bad. If the battery manages to get to 3v, you can kick the charge current up to 500mA.

For a variable voltage supply, measure the voltage of the battery and set the supply voltage 0.5-1v above the battery and monitor the current going to the battery with a multimeter, you'll want to keep it in the 50-100mA range until you get to around 3v and then you should be able to kick it up to 500mA by increasing the voltage output.