[SOLVED] Possibly a bad battery for Thinkpad T400?

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irets · Post by **irets** » Sat Mar 18, 2023 9:01 am

Hi,
I noticed that on my Lenovo Thinkpad T400 the

cat /sys/class/power_supply/BAT0/capacity

was stuck at 84, so I let it drain to zero and recharge.
Coming back after a few hours it's now stuck at 57.

Has my battery gone bad? Is there anything I could do to refurbish it? Should I try to find a site which ships a T400 battery to Finland? What should I check before I come to the conclusion that it's time to find a new battery?

irets · Post by **irets** » Sat Mar 18, 2023 9:06 am

I noticed they sell T400 replacement batteries on laptopbatteryexpress.com but they'd charge $430.15 total for shipping the $78.90 battery to my country.
That is insane.

Post by **NeddySeagoon** » Sat Mar 18, 2023 10:33 am

Irets,

Do you care what

Code: Select all

cat /sys/class/power_supply/BAT0/capacity

says?
If the battery life is not an inconvenience, then no.

The laptop will still work on mains power with the battery removed.
Lithium battery capacity reduces with every charge/discharge cycle. Its a feature of the technology.

Do not buy a cheap no name replacement. That can use cheap unsafe no name cells and may be unsafe.

irets · Post by **irets** » Sat Mar 18, 2023 6:17 pm

Neddy,

This is my only travel laptop that I own so having even a somewhat 'decent' battery life is a plus.
Of course I always have a charger with me also.

I ended up ordering a Green Cell 4400mAh battery for my T400 from a certain online store in my country.
Other reviewers had not had issues with it but I am aware of the risk I am taking by not using an official Lenovo battery.

I think it's impossible to find 'new' official Lenovo batteries for laptops old as this, so second-hand is the best I can do, unless if I look into disassembling the battery myself and refurbishing it, which I do not feel comfortable doing right.

I'll update this thread and report back when I get my battery, if my apartment does not catch on flames and/or I get hospitalized.

EDIT:
Now that I look a the current battery which is in my laptop, I do not see any Lenovo markings.
It's a TradeShop 4400mAh battery. Could the previous owner of this machine have replaced the original battery with this? Or could Lenovo have had a partnership with TradeShop back when they rolled out his machine to the store shelves in 2000s?

sdauth · Post by **sdauth** » Sat Mar 18, 2023 8:06 pm

This is not a good idea to let it drain to zero. I killed my old T400 battery this way (although it was still showing 76% capacity)
On my T400, I always shut it down (if power source is not available) when it reaches 20%. My current no name battery is almost two years old and shows 94% capacity (around 5 hours with low luminosity, non intensive load)

irets · Post by **irets** » Sat Mar 18, 2023 9:03 pm

Sdauth,

Five hours of non intensive load is pretty good. Do you know the mAh capacity on yours?
Are you using any power management software?

Long ago, I remember reading somewhere that letting a rechargeable battery drain to the point where the device powers off is better than having a constant charge on the cells.
Was that bogus information?

sdauth · Post by **sdauth** » Sat Mar 18, 2023 10:14 pm

Irets wrote:Sdauth,

Five hours of non intensive load is pretty good. Do you know the mAh capacity on yours?
Are you using any power management software?

Yes. It is a 4400mAh (the big one).
I was using powertop previously but it requires to enable too many stuff in kernel to work so now I just let xfce4-power-manager do the job instead. And monitor with "watch upower -i $(upower -e | grep BAT)" to have more stats.

Long ago, I remember reading somewhere that letting a rechargeable battery drain to the point where the device powers off is better than having a constant charge on the cells.
Was that bogus information?

To be honest, I read the exact same information years ago

This is indeed confusing. Just sharing my real life experience.
I don't know if it is cell quality related. The previous battery was already a no name one (lasted almost 3 years so it was quite good for the price, 40€ from memory)
On the new one there was a little note in the package warning to never let it go under 20%.
If one cell dies, even if the other ones are still good, it is over. (This is what happened probably although I never bothered to check with my multimeter; it is a pain to open it, by design I guess so you buy the whole battery instead ! Well, still better than glued/soldered batteries on new laptop nonetheless)

szatox · Post by **szatox** » Sun Mar 19, 2023 1:05 am

Long ago, I remember reading somewhere that letting a rechargeable battery drain to the point where the device powers off is better than having a constant charge on the cells.
Was that bogus information?

It's not bogus. The chemistry of NiCd batteries was basically a loop of irreversible reactions, so not going all the way would limit the available capacity.
It is outdated though. Li-ion - which has long replaced NiCd - gets damaged when left discharged. (and also deep-cycled, though to lesser extent).

Post by **NeddySeagoon** » Sun Mar 19, 2023 11:21 am

sdauth,

It addition to what szatox said, a deep discharge and recharge to 'full' does nothing for the battery.
It only recalibrates the battery charge management system.

sdauth · Post by **sdauth** » Sun Mar 19, 2023 12:03 pm

NeddySeagoon,

This mean the battery cell could actually still be ok ? The only thing I know is that I'm unable to charge it anymore after having it let it drain to zero. (fast orange led blinking)
So maybe a bug in the battery firmware ?
Unless there is way to manually reset the battery charge management system (eeprom) ? I don't know of such tool.
EDIT : Found this : https://www.youtube.com/watch?v=6_J_yuI1xMo although it is not cheap.

logrusx · Post by **logrusx** » Sun Mar 19, 2023 8:12 pm

sdauth wrote: This mean the battery cell could actually still be ok ?

Not at all.

sdauth wrote: The only thing I know is that I'm unable to charge it anymore after having it let it drain to zero. (fast orange led blinking)
So maybe a bug in the battery firmware ?

I'm sorry to tell you that means the battery might be gone. This indicates error and if you're unable to charge it anymore it's as good as dead.

Best Regards,
Georgi

szatox · Post by **szatox** » Sun Mar 19, 2023 10:00 pm

An error in BMS doesn't automatically mean the cells are dead though. It could be a response to e.g. undervoltage or a bug or whatever.
This said, bear in mind that Li-ion cells are quite dangerous. The electrolyte is highly flammable, lithium is somewhat explosive, the whole thing should be considered toxic... And they can be set of by short-circuit or overvoltage, not only physical damage.
If you want to salvage some parts, better give this task to someone who knows what he's doing.

irets · Post by **irets** » Mon Mar 20, 2023 7:16 am

NeddySeagoon wrote:It addition to what szatox said, a deep discharge and recharge to 'full' does nothing for the battery.
It only recalibrates the battery charge management system.

Does that mean my laptop battery was bad the whole time but I never knew the full extent of it, until letting it drop to 0% and then get stuck at 57%?
Before the above happened, it was stuck at 84%.
It's a Li-Ion battery.

A deep discharge and recharge did something to it..

logrusx · Post by **logrusx** » Mon Mar 20, 2023 8:42 am

Irets wrote:
NeddySeagoon wrote:It addition to what szatox said, a deep discharge and recharge to 'full' does nothing for the battery.
It only recalibrates the battery charge management system.
Does that mean my laptop battery was bad the whole time but I never knew the full extent of it, until letting it drop to 0% and then get stuck at 57%?
Before the above happened, it was stuck at 84%.
It's a Li-Ion battery.

A deep discharge and recharge did something to it..

That's how it usually happens, but with frequent use of battery you don't notice it and with using it on mostly on mains power you notice it all of a sudden. That's why it's recommended to keep your battery between 40 & 70% charged, that's why thinkpads, at least in the past, have battery charge thresholds.

p.s. I didn't understand, you cant change it at all anymore or you can't charge it beyond that level? If it's the second, you can still use it.

Best Regards,
Georgi

irets · Post by **irets** » Mon Mar 20, 2023 9:18 am

Thanks for the explanation.

logrusx wrote:p.s. I didn't understand, you cant change it at all anymore or you can't charge it beyond that level? If it's the second, you can still use it.

It cannot be charged beyond 57% but still works.

Post by **NeddySeagoon** » Mon Mar 20, 2023 9:40 am

Irets,

The battery management software estimates the remaining charge by measuring charge in an change out over time and comparing that with battery capacity.
Its dead reckoning so errors mount over time.

The deep discharge lets the battery management software get a foot on the ground again by defining zero. (Empty)
The next charge calibrates the amount of charge that the battery can hold, in your case 57% of its rated capacity when new.
Laptop batteries are rated end of life when they can only store 50% of the rated capacity.

Lithium batteries loose capacity with every charge/discharge cycle. Its a feature of the chemistry/construction.

Lithium spontaneously ignites on exposure to water vapour, so a damaged lithium cell is very dangerous. Water vapour is everywhere.
Once the fire starts, its very difficult to extinguish. Water just makes it worse.

Your battery is close to end of life. A good quality replacement is the only option - or no battery at all.
Recycle the old battery properly, so that its dismantled safely.

irets · Post by **irets** » Fri Mar 24, 2023 1:43 pm

Neddy,

Thank you for the in-depth explanation.
I never knew this stuff about laptop batteries.

So, I got my GreenCell battery today in mail and it came with the following instructions:

1. Insert batter into laptop/tablet and turn it on without AC adapter connected.
2. Use the battery until system alerts low battery level (usually 5-10%).
3. Do not let the battery discharge completely, it may cause irreversible cells' damage.
4.Connect the AC adapter and charge battery according to the device's instructions.
5. After 3-5 complete charging cycles, the battery should reach it's maximum capacity.

Good and all... but my battery arrived with such a low charge my T400 could not completely power on, so there likely already is some damage done to the cells.

I'll charge it up completely, let it drop to ~15% and charge up again a few times and see what cat /sys/class/power_supply/BAT0/capacity reports.
The locking lever is also a bit different on this battery compared to my previous one, but it works just as good.

irets · Post by **irets** » Wed Apr 05, 2023 6:59 pm

The problem was with my previous battery.
I now have much longer battery life and /sys/class/power_supply/BAT0/capacity isn't limited to 57.

Thank you to everyone who shared their Li-ion wisdom in this thread. Marking as solved.