Rebuilding laptop battery pack - Page 1
Forum section: electronics / beginners

author: eletronob
author_rank: Newbie
timestamp: March 27, 2019, 09:17:33 am
content: Hello to everyone,Can anyone please help me in this task?I want to replace the batteries from my laptop's battery pack.The battery pack specification: 10.8V, 4.40Ah.Inside there are 6x 18650 batteries Samsung ICR18650-22F, 2200mAh, 3.6V.I searched long time on eBay and the cheapest I found are around AUD 45-50 for 6 batteries which makes no sense because I could buy a battery pack already assembled with bigger capacity for around AUD 60.Then I found batteries which are used for vape torches that are much cheaper and have a bigger capacity, I had to enter a specific description to find these in the hopeless eBay's search engine that they will never fix.The batteries have a Sony code VTC6 and have 3000mAh capacity.This is a sample:https://www.ebay.com/itm/Genuine-US18650VTC6-18650-Battery-3000mAh-High-Drain-30A-For-Vape-Torch-4Pcs-57/333132741593?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D1%26asc%3D20131003132420%26meid%3D111c57615e4546c887aa168838f3f787%26pid%3D100005%26rk%3D5%26rkt%3D12%26sd%3D253918563616%26itm%3D333132741593&_trksid=p2047675.c100005.m1851My question is can I replace the original 2200mAh batteries with these of 3000mAh?The original battery pack includes a mini board.Thanks in advance.

author: xavier60
author_rank: Super Contributor
timestamp: March 27, 2019, 10:20:24 am
content: I have done the same thing. It can be an unforgiving and potentially dangerous job that has to be done right the first time.I will not explain in detail as to how I made the connections. I will say that those paper washers stuck to the + end of the cells are important for preventing connecting conductors from puncturing the cell's plastic covering and causing a nasty short circuit.The various types of protector PCBs can behave in different ways. Some will never work again after the original cells are completely discharged or disconnected. Others will happily work again, sometimes needing a brief charge to wake them up.I have some gutted Toshiba battery shells here that I can connect an external 12V battery to and with a 3 resistor divider to supply the cell voltage sense wires, use to power a laptop. They will even report a useful state of charge.You should assess the protector PCB.Using higher capacity replacement cells is not a problem.

author: eletronob
author_rank: Newbie
timestamp: March 27, 2019, 10:39:37 am
content: Quote from: xavier60 on March 27, 2019, 10:20:24 amThanks for support.What do you mean for assessing the PCB?

author: mariush
author_rank: Super Contributor
timestamp: March 27, 2019, 10:39:44 am
content: 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/52712986.5$ each (with solder tab) :https://www.digikey.com/product-detail/en/sparkfun-electronics/PRT-13189/1568-1490-ND/5271299The ones with solder tab would be more suitable as it would make soldering them together much easier.

author: eletronob
author_rank: Newbie
timestamp: March 27, 2019, 10:47:37 am
content: Quote from: mariush on March 27, 2019, 10:39:44 amThanks very much for information, I was just wondering what was the meaning of these high discharging batteries.But also I may not order because they cannot deliver batteries by air!

author: xavier60
author_rank: Super Contributor
timestamp: March 27, 2019, 10:47:47 am
content: Quote from: eletronob on March 27, 2019, 10:39:37 amIt would be useful to know if it's going to work before you go to the effort of fitting the new cells.One way could be if you can salvage 3 of the old cells that still hold charge and temporarily wire them to the protector PCB to see if it will work in the laptop. Always disconnect the main + lead first and reconnected it last to the protector PCB.

author: eletronob
author_rank: Newbie
timestamp: March 27, 2019, 10:52:26 am
content: Quote from: xavier60 on March 27, 2019, 10:47:47 amOk that is another thing I need to deal with.But I'm looking for a good battery deal anyways because if I'm not able to fix the laptop pack, I'll use them in my next boombox project and they will fit perfectly.

author: Jwillis
author_rank: Super Contributor
timestamp: March 27, 2019, 08:42:36 pm
content: The PCB is the BMS( Battery Managment System). It monitors the charge,temperature ,voltage ,balancing and so on. Check the batteries individually .Many times its just one or 2 bad ones that trigger the BMS to stop charging the pack.But also some BMS need to be reset to function again and it may only be programed for a specific charge rate for the batteries installed.

author: eletronob
author_rank: Newbie
timestamp: March 27, 2019, 09:31:48 pm
content: Quote from: Jwillis on March 27, 2019, 08:42:36 pmThat is what I was suspecting and why I'm asking here for help so probably a bigger capacity or different battery might not charge properly.But the main issue now is that buying 6 batteries costs nearly as buying the entire battery pack and they even have bigger capacity, just we don't know what batteries they put inside.

author: Jwillis
author_rank: Super Contributor
timestamp: March 27, 2019, 09:55:44 pm
content: http://gamma.spb.ru/media/pdf/liion-lipolymer-lifepo4-akkumulyatory/ICR18650-22F.pdfbut you can put any 2200mah 18650 battery in there.I would myself go for something from a reputable dealer . In many cases the really cheap ones are just factory surplus to keep stock fresh or they may be cheap crap to.Really difficult to say unless you take a chance.

author: amyk
author_rank: Super Contributor
timestamp: March 28, 2019, 12:34:47 am
content: Quote from: mariush on March 27, 2019, 10:39:44 amThe 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?

author: eletronob
author_rank: Newbie
timestamp: March 28, 2019, 06:02:43 am
content: Quote from: amyk on March 28, 2019, 12:34:47 am

author: james_s
author_rank: Super Contributor
timestamp: March 28, 2019, 03:56:34 pm
content: 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.

author: Jwillis
author_rank: Super Contributor
timestamp: March 28, 2019, 08:38:34 pm
content: The big chip bq20z955http://www.ti.com/lit/ds/symlink/bq20z95.pdfandhttp://www.ti.com/lit/er/sluu264a/sluu264a.pdfFrom 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.

author: amyk
author_rank: Super Contributor
timestamp: March 29, 2019, 01:18:58 am
content: I see thefusehas blown, probably due to the protection circuitry explicitly doing it. This pack is not going to be an easy one to rebuild.

author: eletronob
author_rank: Newbie
timestamp: March 29, 2019, 01:26:54 am
content: Quote from: amyk on March 29, 2019, 01:18:58 amWhere is the fuse?

author: amyk
author_rank: Super Contributor
timestamp: March 29, 2019, 03:01:45 am
content: Click the link and look at the pictures

author: Jwillis
author_rank: Super Contributor
timestamp: March 29, 2019, 10:45:33 pm
content: That is a D6 type Combined Thermal Fuse/Resistor. and you can't visually tell if its blow from that side .The fusible links are on the other side under a plastic enclosure.Theirs probably nothing wrong with it but you check continuity between 2 and 3 ( the fusible links) and should see a resistance between (1 and 2 ) and (1 and 3) .The resistance is the heater

author: eletronob
author_rank: Newbie
timestamp: March 29, 2019, 11:03:02 pm
content: Quote from: Jwillis on March 29, 2019, 10:45:33 pmThanks very much, that is a very clear and helpful information.Quote from: amyk on March 29, 2019, 03:01:45 amSee how it's done.