Laptop Batteries

Just retired a couple of 9 year old Thinkpad laptops but want to keep at least one in a working state as can be very helpful if current system goes down for any reason. Batteries in both still perfectly usable at present but what's the best regime to keep them that way, permanently plugged in or just allowed to fully discharge?

 

Neither.

If those were the only two options, it would be better to leave them plugged in. This is because the intelligence in the battery itself, and the laptop's charging circuits ensure the batteries can never be overcharged - a very good thing. But of course, that assumes those overcharge protection circuits are, and remain working perfectly. Not sure that is safe to assume with any 9+ year old electronics.

It is never good to put a fully discharged battery into long term storage. This is because the internal chemical processes that product the electricity is still going on, though at a much slower rate. Still, the batteries will continue to slowly discharge, even sitting on the shelf. At some point, they will discharge to the point of no return. Not good.

So typically, the best solution is to charge the battery to around 75% charge, then put it in storage, in a cool dry place. Then every so often (I would start with every 6 months), fire the laptops up, update them to make them current - especially for security, recharge back up to 75% and put them back in storage.

That said, expect, one day, it will not come back to life. So don't keep any data on them you don't have backed up somewhere else.

 

Will do, thanks.

 

Thanks plodr, you are leading me into a field I really know next to nothing about. Anyway I've been looking into the current state of one of the laptops, which has been left with its battery connected but unpluggged from the mains for about a month now. From plodr's post I was intending removing it and putting it into storage at about 40%, probably in about an hour. Any further advice or observations?



The column headings btw are Current, Min and Max

 

Maybe I'm not understanding this fully plodr. The first 40 is the state of charge, no problem, but as I read it the second 40 is 40 degrees F and the only place I have for that would be on the top shelf of a fridge. Is that right or my misunderstanding?

Anyway, both batteries are now around 40% SoC and put away in a cool room, currently about 18C. I'll take another look at them in about 3-4 months time and update here.

 

I think she means not discharging below 40% of battery power......and not recharging above 40

 

Thanks for the clarification plodr. Looks like they should be ok where they are now but I will update in April. The results might throw a little light in a rather dark corner

 

So here we are about four months later with just about enough juice to start the old laptop from battery but needing to recharge it to do anything at all. Clearly the four month rest hasn't been helpful, with the battery capacity substantially reduced and the wear level significantly increased. Don't have any comparisons but can't avoid feeling that it would have been far better to just leave it connected but unused rather than removing the battery and keeping it at room temperature but your comments would be appreciated.

I used CPUID HWMonitor for the tests

 

Yeh, my 8 yo Toshiba Sat lappy (dual core, 4G ram) has been a workhorse.
Battery good for a boot but not much longer.

She will go out to pasture soon so not worth replacing battery.