I’ve a Fujitsu Laptop that I use in spurts. Sometimes it’s in daily use being lugged around with me constantly, other times it gets left on the table under a pile of paperwork and not used for weeks at a time.
Recently I switched it on and the battery was flat and then found that it refused to charge. It’s around four years old so I thought that it had probably just come to the end of its life. The Laptop kept saying it was 98% charged but the charge indicator wasn’t illuminating.
I wondered if perhaps just one of the cells in the pack had failed (and the others could be useful for other things) but then I had a thought; I’ve seen this before with other so called “smart” battery packs. I took out my trusty Dremel power tool and carefully cut into the pack where I suspected the intelligent battery monitoring circuit was.
Once I’d cut into it, I could see the two connections going to the cells and placed a volt meter across them. The pack was reading 9.1v.
I set by bench top PSU to 11v and hooked it directly across the terminals. I applied power for around 5 seconds, removed it, waited a few seconds and repeated a few times. After each cycle I would check the pack voltage and slowly it started to climb. Once I got the pack up to around 10v, I quickly inserted it back into the laptop and switching on the power. Hey presto, after a couple of seconds the charge indicator came on and Windows reported the pack was 4% charged… and charging. I left it charging whilst I got on with other activities keeping a fairly close eye on things (these retched batteries have a habit of catching fire) and after around 90 minutes or so, Windows reported the pack was fully charged and this was confirmed by switching off the mains power and the laptop happily running on its battery pack whilst reporting around 90 minutes of run time available. This is about right for this laptop.