Dual battery mod for your struggling laptop

Thread Starter


Joined Oct 13, 2017
Let me preface this by saying I do not really care about this laptop so I was willing to have some fun with it. That being said, here are the results of my dumb little experiment on giving my laptop an extended battery life.

My original battery was starting to struggle a bit to even last 3 or 4 hours of light usage so I purchased a replacement pack. Rather than throwing away the old pack I instead ran the individual cells in parallel with the new BMS. I know it won't be the most aesthetically pleasing design but it should be way more efficient than running an external battery bank.

It's a Pavilion x360 with a 3 cell lithium Ion pack for anyone wondering.
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Here is how I did it, Popped off the old BMS and connected up each of the old cells to the new cells bms. Fed the wires through a hole I drilled through the bottom of the laptop (I'm in too deep at this point).
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So other than the fact that I will never be allowed to take this thing on an airplane, the mod did "work". But there are definitely some interesting drawbacks. I installed this application which would tell me the voltage and current level of my battery, just to see how it would react.

This was the initial reading of the old pack.
old pack.png

After the first initial charge, it was most definitely confused. As much as I would love 174 hour battery life, I don't think that's the case. It wouldn't budge from 100% for quite some time and then jumped in percentage. Voltage is still quite high.
after first charge.png held at 100%.png initially discharging.png

When the laptop was finally about to die that was when the fun started. It was reading 5% but it still just barley hit the nominal voltage of the packs. It should have a good amount of run time left but it shut down. I powered it up with a charger and ran a command which would disable the laptop form hibernating at 0%. It was reading 0% for 4 hours on max brightness with performance mode. (the voltage was also increasing for some reason, so I'm starting to question the reliability of the volt meter)
changed settings, held at zero..png

I'm aware that technically even though they are the same battery, the older one will have a lower capacity and will strain the newer one. I'm assuming this strain will be much less than the gain in capacity provided by adding the old battery in the first place. Also the weight of the additional battery is barely noticeable which a is a bonus, and just 5mm thick.

Over all the battery mod "worked", with all the settings cranked up I can get 11-12 hours of screen on time and with power saving mode I imagine I could easily hit 16 hours. The only problem is I have no way of knowing the percentage of my battery. I can always view the voltage of the pack but that's not very reliable. If any of you guys know a way I could actually modify the windows voltage readout that would be ideal. I have cycled it from 0 to 100 many times to try and reset the coulomb counters but it still only monitors the top 50% of the battery. I even ran the disk analyser in the bios to force the battery to drain to zero and that did not reset it either.

I'm currently trying to find a program that would be able to monitor the battery independent of the windows readout but they all rely on it from what I've seen. If any of you guys have ideas on how I could improve it I would love to hear it. I will be 3d printing an enclosure for the battery to make it look less like an explosive very soon.

Fun fact: If windows thinks my battery is dead and I shut down the laptop it will not let me boot it back up even though there is 50% battery left. I have to jump start it with a charger haha.