Laptop battery takes days to charge

Ottavio Caruso · 2024-01-17T11:55:28+00:00

I have a run down, battered old Thinkpad that I basically use as a desktop at home because the motherboard is cracked and doesn't stand being carried around. Apart from that, it used to work well. I connect it to my other laptop via ssh that acts as a file server and poor man's AP.What happens now is that the battery drains even when the charger is connected. If I switch the laptop off (I mean completely off, not hibernated or suspended), it would take 3 days to bring the battery back to 100%, and provided I don't turn it on in the meantime.The green light on the motherboard blinks when the battery is in charging mode but is solid when it is waiting to charge.According to the battery diagnostics, the battery has a capacity of 83%. Not great, but still good enough. My other laptop (different Thinkpad) has a battery capacity of 10% but it doesn't drain when the charger is connected.I have set the battery limits (tlp to start charging when the battery goes to 1% (yes, 1%), otherwise the charger goes completely bananas. Then I have to manually set the charger to charge ("tlp fullcharge") and shut the laptop.Considering that the laptop is almost dead and that a new battery is about £50 and a compatible charger is about £20, how do I know exactly if the problem is due to:a) the battery;b) the charger, orc) the motherboard?I would also hate throwing it away, because I am a good citizen and the only authorized skip for electronics in Birmingham is miles away.

Jan 17, 2024 Last reply: 2 years ago 24 Replies

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Roland Perry 2 years ago

In message <Edp* snipped-for-privacy@news.chiark.greenend.org.uk>, at 19:21:34 on Thu,

18 Jan 2024, Theo <theom+ snipped-for-privacy@chiark.greenend.org.uk> remarked:

If it has such a battery, but I don't recall seeing one for decades.

My latest laptop is a bit posh, and has hot-swappable main batteries, plus a tiny built-in rechargeable battery to keep it going while you do the swap (and also to keep the machine's setup when it's gone to sleep).

Desktops tended to go for an RTC/set-up-RAM powered by an embedded 10yr battery, rather than exchangeable coin-cells. Which is great until the desktop is more than 10yrs old, but they didn't really care.

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Theo 2 years ago

They are common, eg:

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Some of them have a rechargeable NiMH cell on a wire plugged into the board:

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which the laptop theoretically trickle charges. That can go flat, and it can be worth a try to charge it outside the laptop and re-connect it:

I'd guess there must be a separate settings battery, since those batteries that run the system would be easy to run flat?

I've not seen them with a primary 10yr cell, are you sure they aren't NiMH cells like the laptops?

There were some RTCs with a lithium primary cell integrated into the chip module (eg Dallas Semiconductor, latterly Maxim), but those were in the

286/386/486 era.

Theo

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Roland Perry 2 years ago

In message <+eA* snipped-for-privacy@news.chiark.greenend.org.uk>, at 21:47:54 on Thu,

18 Jan 2024, Theo <theom+ snipped-for-privacy@chiark.greenend.org.uk> remarked:

That's a scrap motherboard from an extremely low-end laptop. Apologies for not having seen one myself.

The battery settings are for the hot-swappable ones. The built-in battery powers it for about two minutes (full functionality, screen on etc) according to the test I did just now, which is vastly in excess of the time it takes to change the swappable one.

Reasonably so, yes.

And your theory is they reverted to a combination of unpowered RTC and button cell?

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Pamela 2 years ago

Is the OP's battery NiMH or lithium-ion?

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Theo 2 years ago

The battery that's not charging is lithium ion, but a reason for it not charging can be flatness of a small settings battery, which can be either primary lithium (CR2032 usually) or NiMH rechargeable.

Theo

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