Notebook Battery Balancing Sucks

TL;DR: Don’t trust the vendors. They only monitor the cells, they don’t balance them.


It’s a less known fact that most notebooks don’t balance their cells. So I added an active balancer


Buy it here:

What is this?

This is not a regular bleeding balancer but an active balancer. It uses inductors to transfer energy between the cell levels to keep them equal. That gives us:

  • more energy efficiency. That is not only great in itself, but it enables this balancer to really make unused capacity of one cell usable.
  • it workouts throughout the whole voltage range. Regular balancers start working at 4.25V which is seldom reached in notebook cells

ETA3000 is the IC name.

You get the Idea. It’s a combined Buck-Boost converter.

The Modification

I tried it out with the stock connections to my notebook battery. I added a halogen bulb as load and the active balancer started balancing.

Notebooks are filled with all kinds of stuff. It’s unrealistic to cram in a lot more PCBs. So I filed it down and unsoldered the bulky connector.

Here you can see my handmade connector. It uses 1.27″ pin headers. I used a spare pin to block the connector mechanically against reverse polarity.

I found a spot where I could cram it in. I also like Kapton tape. It stays alive to ~300°C.




None yet. I’ll have to check it. Capacity for this 3-month-old battery has gone down to 64.9002 Wh from 97 Wh originally.