Upgraded Laptop Battery

[werto165]

I know that quite a lot of laptop batteries are based off 18650 cells do you think it would be possible to buy a new laptop battery and swap the old cells for newer larger capacity cells? I've been looking and the IC for the battery management system (charge controller?) anyway reprogramming it needs kit that costs about £100 whereas a new battery is only about £20 so I thought that would be a better route. Would it be possible to place more cells in parallel to get greater capacity and perhaps 3D print a new enclosure for the improved battery? I know that spot welding is probably required but my university has that capability so I would be fine in that regard 

 

 

https://www.ebay.co.uk/itm/18650-3-7V-4000mAh-BRC-Rechargeable-Li-ion-Battery-Lithium-Cells-UK-Seller/263876035192 18650 cells 

https://www.amazon.co.uk/Replacement-Pavilion-800049-001-800010-421-HSTNN-DB6T/dp/B07DQKXD5G/ref=sr_1_7?crid=1MIWEEQ1DRLVY&keywords=hp+pavilion+battery&qid=1562852302&s=computers&sprefix=hp+pavilion+b%2Ccomputers%2C157&sr=1-7 battery I'm thinking of taking apart

[ColinLTT]

Yes, its doable and lots of people have videos on YouTube describing the process. That being said, I generally advise NOT to mess with LiPo's if you don't explicitly know what you're doing.

[mariushm]

Those batteries are FAKE.

There's no battery in the 18650 package capable of 4000mAh - it's simply not possible with today's technology to achieve that number.

The highest end batteries in the 18650 size reach around 3200-3500mAh but they're very expensive.

The batteries that are mass produced, in volume, are typically in the 2500-2800mAh range.

Here's examples:

 

Cheap Chinese batteries imported by Sparkfun : 2600mAh : https://www.digikey.com/product-detail/en/sparkfun-electronics/PRT-12895/1568-1488-ND/5271298

 

11 uk pounds each / 50pcs Brand name (LG INR B4 2600 mAh) : https://uk.farnell.com/ansmann/1307-0000/li-ion-battery-3-6v-2600mah/dp/2723326

14 uk pounds each / 50pcs Brand name (LG INR MJ1 3500mAh) : https://uk.farnell.com/ansmann/1307-0001/battery-non-rechargeable-3-6v/dp/2889326

^ they can be found cheaper, this particular store is just more expensive (they factor in the shipping costs in the price)

 

The battery on Amazon is basically just 4 batteries in series : 3.7..4.2v x 4 = 14.8+ ... you can see in the pictures they're rated for  2200mAh so most likely they use 2300-2500mAh batteries inside and they're a bit conservative on the total rating.

 

You can increase the capacity of such batteries by adding batteries in parallel :

 

but you must be careful not to mix old batteries with new, because they'll charge at different rate and their maximum voltage may also be slightly different.

Also, the batteries should have the same capacity, basically best to have all same brand, same series, same max capacity to get same charge rate, same discharge rate and so on...

 

The way I would mod a battery would be by carefully soldering a couple of wires to the circuit board and feed that with a voltage close to battery voltage from an adjustable power supply for example, then remove the old strip of batteries and connect the new strip of batteries (with 2 batteries in parallel instead of just one) - basically at no time the circuit board should be disconnected from power as that could make the chip reset or think the battery pack was damaged.

You'd need a high quality soldering iron that can quickly solder wires without overheating batteries.

Then fully discharge the battery as that would probably make the protection chip "learn" the new peak capacity as the batteries charge up

[lal12]

Hmm it might not be that easy, I tried that once and it pretty much failed. The problem is that the battery has a chip, which counts the charging cycles and capacity of its cells, sometimes this can be resetted, however for many models there is no known way to reset it.

[Hackentosher]

On paper, yeah sure, but it would probably be a pain right in the cunninglinguals to fold up the cells and the tabs like they are from the factory. Definitely only add more cells in parallel though, and remember that you're only allowed up to 100W/hrs per battery operated device.