This blog is about the State of Charge.

The state of charge (SoC) defines the amount of stored energy relative to the total energy storage capacity of the battery. Depending on the battery technology, different methods are used to estimate this value.

The units of SoC are percentage points (0% = empty; 100% = full). An alternative form of the same measure is the depth of discharge (DoD), the inverse of SoC (100% = empty; 0% = full). SoC is normally used when discussing the current state of a battery in use, while DoD is most often seen when discussing the lifetime of the battery after repeated use.

Why can’t the SoC (state of charge) of a battery be measured directly?

It’s important to keep in mind that batteries are not digital devices. They’re a chemical process. Think about what state of charge means. If you see 75% SOC, then that means you have 3/4 of the total capacity of the battery left.

If you want to know more about the State of Charge, you can click here.

How does a cell phone measure how much battery power is left?