Laptop Battery Replacement (another attempt...)

Hi There,

I am aware that replacing the cells is pretty difficult, as you might need to reset the eeprom inside the charging circuit....but this is my situation.

Laptop A) Almost new Lenovo with 5.6Ah battery. Battery used not more that 10 times in 6 months, and laptop flooded. I have the battery which was not flooded with the laptop itself. LG Cells inside.

Laptop B) pretty old but decent laptop with worn out battery.

What if I get a new, rated 5.2Ah cheap battery on Ebay (20 bucks) and replace the cells with the ones taken out from the laptop A) battery? There is a capacity difference, but I guess it should work (and indeed, the quality of the cells is going to be different).

Any particular care I should have while substituting the cells ? Is it a good idea?

Thank i advance!

Replacing cells is very tricky. You have to keep the BMS powered and in a "normal" state at all times. If it detects any abnormal conditions it may blow a chemical fuse, and then it will never function again. It might work to splice in a new parallel pack then cut out the old one. They'd have to be matched very closely since if the BMS sees too much of a voltage change it may blow the fuse. Further, if the BMS has a hard cycle limit (e.g some Dell batteries), it won't help to put in new cells since the BMS thinks the batteries have too many cycles to function safely, so it will prohibit use. Further, you cannot reprogram/reset the BMS without knowing a password. So it is difficult if not impossible for modern batteries.

I think you will find it easier to buy a complete battery pack and sod the cost.

R: Laptop Battery Replacement (another attempt...)

Hi All,

Thank you for your answers.
Indeed, it's easier to buy a new pack.. And this is exactly what I am doing.

However, all the original or reliable pack are rated 4Ah only... I found a Chinese one rated (hopefully not a fake) 5.2Ah. I guess very cheap cells are put in, and that's why I was thinking about buying the cheapo 5.2Ah Chinese pack and replace the cells inside with the ones I have at home (parallel of 2.8Ah, thus 5.6Ah). They won't be charged at 100% probably, but it should work (after carefully following all the steps suggested).

What do you think? It's an old laptop, it's value probably does not exceed 120 bucks....

Inviato dal mio GT-N7100 con Tapatalk 2

Re: R: Laptop Battery Replacement (another attempt...)

Hello Starflex,

Your idea has merit but it is not without risk...

There is risk associated with opening up a battery pack and replacing the cells. If you do this be sure to pay attention to connection wire routing to minimize issues there.

There is also risk associated with how the laptop charger will interface with the new battery pack. Remember that many of the problems with Li-Ion cells and battery packs occur during charging.

Other than that you should be good to go. Who knows, you may even increase the value from 120 - 150 bucks...

Tom

Guys,

Work done with good results.

The replacement Chinese battery arrived (it was rated 5.2ah..fake capacity declared, as often happen ), I just checked its functionality and, without charging it, I opened it and I replaced the cells with the LG - 2.8 (parallel, so 5.6 ah) I had.

As recommended, I connected the replacement cells keeping the original ones in the circuit (so that the IC was always under power).

Battery pack it's working fine : I am cycling it now and the capacity (checked via software..) is increasing, from the equivalent of 4.4Ah (original true capacity) up to 4.9 ah (now via software I can read 109% of the rated capacity. Not a big difference but, again, at least I know that the cells inside are now 'branded' cells and not un know ones.

Thank you all!

AM
Gauss163 is right, You need to keep chip powered all the time during replacing the cells. If it detects any fault condition then PF (Permanent Flag) is set and the battery cannot be used anymore. If you succeed to replace the cells and PF is not set then you need to perform a calibration in order to update the dynamic parameter FCC (Fully Charged Capacity).