Just like with humans, one simple medical test doesn’t provide a complete health status

While knowing your battery’s SoC is certainly helpful, it doesn’t tell the entire story. Each time a battery is recharged, the fuel gauge is reset to 100% — regardless of its SoH.  This means that even an aged battery shows 100% after a full charge, while the charge acceptance may only be 50% (as we still don’t know the runtime of the pack). For this, you need to measure the SoH, which is a bit more complex.

Here’s how this process works: Each battery, at its time of manufacture, is assigned a specific SoH status which is 100% by default. Remember that with each charge, the battery resets to the full charge status. During discharge, however, the energy units are counted and compared against this 100% full charge setting. As the battery ages, and the charge acceptance drops, the overall SoH decreases. So, it is this discrepancy between the factory-set 100% status and the delivered energy units on a fully-charged battery that indicates its overall SoH.

Like with our own health, we can only “recharge” so many times before our overall health status is negatively affected. Smart choices are always healthy choices.