I have a new charger with mAh measurement – does that mean I can check the capacity of the battery?

During charging, we can only assess how many mAh the charger has „pumped” into the battery, to determine that it is already full. If we try to charge a battery that has already been charged, the measured value may be very low, having no relation to the full, nominal usable capacity.

While in the case of Li-ion cells, the mAh used for charging often translates almost 1:1 to the actual usable mAh capacity obtained later from discharge, in the case of Ni-MH cells, the information about mAh from charging carries very little usable value. This is due to the fact that during the charging of Ni-MH cells, there are certain significant losses, which are not constant and can vary significantly between different batteries, or depending on temperature/environmental conditions.

In summary, the mere fact of measuring mAh in the charger does not determine its ability to measure the actual usable capacity.

Only a proper, full capacity measurement from discharge allows for a reliable assessment of the battery's quality, or checking the manufacturer's credibility regarding the declared nominal capacity of the tested cell.

Discharge will also be necessary to check the capacity of a single-use battery, or when assessing the self-discharge effect of the battery. Without this function, it is impossible to perform extended diagnostics to resolve compatibility issues between batteries and the device in use.

We describe the topic of proper capacity measurement in more detail in another post:

https://www.hurt.com.pl/blog/jak-poprawnie-zmierzyc-pojemnosc-akumulatorka-aa-1-2v-lub-18650-3-7v-w-ladowarkach-z-pomiarem-pojemnosci-73

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