Replacing Li-Po batteries on laptop batteries

Thread Starter

DudeThuRein

Joined Feb 2, 2024
1
Dear all,

My laptop battery is 3 (3.7v each) Li-Ion cells 11.1v and the capacity of the cells is 2600mah each. It is now very old and I can only use about 45 minutes without external power supply.
So, I was thinking to replace the cells with higher capacity cells. And I have 3 (3.7v) Li-Po Cells, each one has the capacity around 6000mah.
Would it be safe to I replace the Cells from my laptop battery with the Li-Po batteries I mentioned above?
I'm afraid they would explode.
Please tell me anything that you know or you experience or your opinion about the set up I'm thinking.
Thank you very much in advance.
 

Ya’akov

Joined Jan 27, 2019
9,150
Welcome to AAC.

The answer to this question depends on the computer’s BMS (Battery Management System). The three cells in the existing pack are in a 3S1P (3 Series, 1 Parallel) configuration. That is, they are in a series (3S) and the only series set (1P).

When batteries are made of cells in a series it is very important each cell be kept very close to the same voltage. If not, over time the lower voltage cells being charged by the higher voltage will suffer heating and damage. This is handled by a BMS feature called balancing.

For balancing to work there is a separate connection from the BMS to the positive terminal of each cell so they can be charged independently as required to keep them in sync. This should be present but is sometimes omitted to save money making the battery life shorter.

If there is no balancing, you will probably need to add a balancing BMS yourself. You can get them pretty cheaply, and the charging input and power output would just look like the combined 3S battery. This might work with the existing BMS or you might have to charge the battery independently.

If there is balancing then you will have to ensure it is properly wired to the new cells. In any case, I would put individual protection boards on each LiPo if they don’t already have them to prevent over- or under-voltage damage, or even risk of fire.
 

KeithWalker

Joined Jul 10, 2017
3,091
You will probably not succeed. Laptop batteries have a small chip inside that controls/monitors the charging process and also monitors the number of charge/recharge cycles. This chip is factory programmed with information how this sort of battery typically degrades over time. If you replace the cells in the battery, you will lose the factory program on the chip and the battery will be useless.
The manufacturers do this to ensure that you have to replace the battery pack with one of their own expensive packs.
 
Top