18650 batteries taken out from laptop battery now charge

Hi, I,m confused - the battery from my compaq laptop which is about 5 yrs old would not hold its charge for more than 5 min. I decided to open the battery and took out all the 18650 batteries - they were all about 3.75 v. I recharged all with my 18650 charger - all charged fully and are holding their charge.

Now comes the confusion - since all batteries are now fully charged why could the computer not charge them.

Also, I left the battery in the computer all the time - contrary to what I have read, this obviously did the batteries no harm

Protection circuit gone bad.

But at 5 years old I'd not expect any of the cells to hold a charge for very long.

Recently I salvaged some Samsung cells from a dead laptop pack. All of the batteries charged nicely to 4.2V and I was happy. I sent one to my friend Mitro to test and it only had around 40mAh. My happiness was shortlived.

A good measure of dead-ness would be charging them to 4.2V, letting them rest 24 hours and test again - if voltage has fallen significantly, don't expect anything good out of these cells.