My old dissipative balancer

A project log for Low-Cost Non-Dissipative Active Battery Balancer

This cell balancer will transfer electrical charges from a strong cell to a weak cell. Ideal for electric vehicles.

afdhal-atiff-tanAfdhal Atiff Tan 04/01/2017 at 18:260 Comments

I use my ebike daily to get to work. I need it to be as reliable as possible. Before starting this project, I use a simple balancer to top-balance my 14S pack on my ebike.

I prefer top-balancing instead of bottom-balancing because I am using recycled cells, none of them are matched in term of capacity. This means it is difficult for me to ensure full charge on all cells.

Other than the stored charge, the internal impedance of the entire pack is a lot higher for bottom-balancing because all of them are discharged at the same time. Although it is safer, that will make the other healthy cells unused.

The balancer worked ok, but, the shunt transistors get untouchable hot at each end of the charge cycle.

Because of this, I decided to find an alternative that does not generate dangerous wasted heat.

After few hours of research on google, I found a scheme called "active-balancing". Unfortunately, all of the solutions that I came across are expensive and the parts are difficult to source.

I am tempted to make an Arduino based controller for it, but, the mosfet and its driver gets expensive quite quick if I wanted to scale it up.