Electronics > Projects, Designs, and Technical Stuff

Hacking A Laptop Battery

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The battery on my HP laptop recently kicked the bucket. I'm looking to see if I can get a replacement, but I would rather make my own, reason being that this machine takes a fair bit of power to run, and even when I first got it I could only push the battery to 2 hours at most. Add to that the bad placement of air intakes, and things got silly. I would like to build my own little set of batteries that both elevate the back end of the machine, and provide power for longer periods of time. The thing is that there are multiple pins on the battery (6 if I recall correctly), and I'm guessing that they aren't all for power. Some must be for data from a controller of some sort that's in the pack.

I'm also wondering what I'll find if I go poking around in there. I know most battery packs on laptops are just off the shelf cells that get shoved into a housing, but I'm wondering if this battery pack has some other cells that could be dangerous if I crack the pack open.

Most laptop battery packs contain a circuit that monitors individual cell voltages and temperatures, identifies the battery's model and total number of charge cycles, and so on.

You could replace the cells if you can find a comparable replacement, but engineering an entirely new battery pack with a different capacity may be more difficult.

revive the built in circuit, replace the cells with any compatible. if you are me, i'll take it apart before its totally dead, "characterized" the cells (voltage), have a rough look at the circuit and find out if "hack possible" and find the compatible cells/battery and start modding. and if you have extra buck, buy a spare battery, in case your mod dont work out well. my 2cnts opinion.

Lithium Ion packs in laptops are part of an engineered system. If you can find the exact same cells used in the pack, it is possible to safely rebuild it. Attempting to modify the pack, different cells, different capacities etc. will all cause problems with the on board charging system that was designed for a specific capacity/brand/type of cell. Most likely you'll have 18650 cells inside, but depending on who made them and when, the actual charging specifics can vary... higher or lower peak voltage and discharge limits. It's not something to fool with, failure of one or more cells can be accompanied with the always delightful "Vent with Flame" event.

If the laptop is of use to you, then spring for a factory replacement pack and relax. If you must tinker, I'd would build an external pack with cables to the laptop and devise a separate charging system.... The so called hobby chargers come to mind, as then you can set the charge rate and such to suit the pack you built. Not a very convenient way of doing things, but if you must, you must. Me.... I'd just buy a replacement from the manufacturer..... that "Vent with Flame" event, while highly entertaining at a distance, really sucks when it occurs in your lap.

That's my $0.02 worth....



I've just been through this exercise with my IBM laptop (R50p about 2004 vintage)
It's not bad specs for and old machine and the only problem was that the battery was not holding charge for long.

The IBM/Lenovo batteries were about $230 each so I went for a Chinese 'equivalent', actually a couple of them from different sources.
So far, no problems. The Laptop recognises the battery capacity and reported charge/recharge times seem reasonable. No overheating that I can detect.
I did consider rebuilding an existing battery but getting the pack apart, sourcing cells with (hopefully) the same specifications, was all too hard.

Should my laptop burst into flames, I'll be sure to report it here.  ;)


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