Does a lithium ion battery have a balance problem?

If you built a lithium-ion battery and its capacity is not what you expect, then you more than likely have a balance issue. While it's true that cells connected in parallel will find their own natural balance, the same is not true for cells wired in series. Battery cells in series have no way of transferring energy between one another.

What is battery balancing?

Battery balancing equalizes the state of charge (SOC) across all cells in a multi-cell battery pack. This technique maximizes the battery pack’s overall capacity and lifespan while ensuring safe operation.

Do you know how to balance a lithium battery pack?

Whether you are new to battery building or a seasoned professional, it's totally normal to not know how to balance a lithium battery pack. Most of the time when building a battery, as long as you use a decent BMS, it will balance the pack for you over time. The problem is, this can take a very, very long time.

How to keep a lithium ion battery balanced?

In Li-ion batteries which have very low self-discharge and therefore accumulative unbalance per cycle is usually less than 0.1%, bypass current of internal FETs is sufficient to keep the pack continuously balanced.

How do I bottom balance a battery pack?

To manually bottom balance a battery pack, you will need access to each individual cell group. Let’s imagine that we have a 3S battery and the cell voltages are 3.93V, 3.98V, and 4.1V. Connect one end of a load resistor to the junction between cell group 2 and cell group 3.

Can you put a Li-ion balancer in a battery pack?

You can also place a li-ion balancer in your pack to perform active cell balancing, increasing the lifetime of your battery pack. When you wire an active balancer in your pack, you want to make sure that the balancer matches the series groups that you have in your pack.