Electronics > Beginners
Rebuilding laptop battery pack
amyk:
--- Quote from: mariush on March 27, 2019, 10:39:44 am ---The "high drain" batteries used for vaping may not work well with a laptop that's slowly discharging the batteries over long period of time.
Think about it ... you have a laptop averaging 20-30 watts from battery pack, so around 1-2A discharge from batteries, and you use batteries "optimized" for high discharges of up to 30A, for brief periods of time (suck on the cigar for a few seconds, then idle for much longer, giving battery time to recover)
The vape battery may also have issues charging at the higher currents.
Digikey stocks some 18650, for example some asian stuff rebranded by Sparkfun :
6$ each (no solder tab) : https://www.digikey.com/product-detail/en/sparkfun-electronics/PRT-12895/1568-1488-ND/5271298
6.5$ each (with solder tab) : https://www.digikey.com/product-detail/en/sparkfun-electronics/PRT-13189/1568-1490-ND/5271299
The ones with solder tab would be more suitable as it would make soldering them together much easier.
--- End quote ---
The main problem with high-drain cells is they also have higher self-discharge and usually lower capacity, but in this case his proposed replacement has higher capacity; the protection board may either not like it and stop charging at the limit of the old cell's capacity or it may need a few full cycles to "learn" the new capacity. Charging current doesn't need to change, it'll just take longer to charge (and discharge ;) ).
As others have mentioned, the BMS will determine how easy it is to swap the cells. Which chip is it? Is the fuse (the 3 terminal device near the terminals on the left in your picture) still intact?
eletronob:
--- Quote from: amyk on March 28, 2019, 12:34:47 am ---As others have mentioned, the BMS will determine how easy it is to swap the cells. Which chip is it? Is the fuse (the 3 terminal device near the terminals on the left in your picture) still intact?
--- End quote ---
james_s:
I've rebuilt several laptop batteries but only because I got a pile of new but obsolete battery packs from a former job from which to harvest cells. I already had a capacitive discharge spot welder and nickel strip. The biggest challenge is the "intelligent" pcb, many modern batteries keep a cycle count and won't let you fully charge a pack with a lot of cycles.
Jwillis:
The big chip bq20z955 http://www.ti.com/lit/ds/symlink/bq20z95.pdf and http://www.ti.com/lit/er/sluu264a/sluu264a.pdf
From what I understand a reset can only be done by programming which is way beyond my capabilities.
"Once the PF has tripped, they can only be cleared by sending the Permanent Fail Clear Key. The default key is 0x1712, 0x2673. The command is only available in Unsealed, Full Access mode".
Whatever that means.
amyk:
I see the fuse has blown, probably due to the protection circuitry explicitly doing it. This pack is not going to be an easy one to rebuild.
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