What is the actual capacity of the everActive 9V Lithium+ Professional Line Li-ion battery - 500 mAh or maybe 1000 mAh?

We have written about it many times, but it is worth making it clear once again - capacities expressed in mAh can be compared and evaluated only if the output voltage of a given battery/rechargeable battery is known to us and it is the same (or very similar) between all the compared products.

In fact, the described everActive Lithium+ Professional lithium battery, which is a replacement for a typical 9V battery, actually uses two 3.7V Li-ion cells with a capacity of 500 mAh each. Also from the technical point of view, this battery has batteries with a nominal voltage of 3.7V and a total capacity of 1000 mAh, and there would be no formal error in such a provision.

The value of 500 mAh, however, appears in the technical data refers to the final product, which offers a voltage at the output 2 times higher - the average nominal operating voltage of this battery is 7.4V. In order to increase the voltage from 3.7V to 7.4V, the 2 cells that make up this battery were connected in series. With a series connection, the voltage of all connected cells is summed up, but the capacity expressed in mAh does not change.
Only in the case of a parallel connection does the capacity of the mAh add up, but the voltage then remains unchanged.

As we described in the case of problems with interpreting the capacity in Powerbanks, the topic is easier to understand using the unit of energy expressed in mWh. A battery with a total capacity of 1000 mAh at 3.7V has a cumulative electricity of 1000 mAh x 3.7V = 3700 mWh.
In the case of a simple change in the battery configuration, resulting in a change in voltage from 3.7V to 7.4V, the total energy will not change (after all, we did not add or take away any cell) and will still be 3700 mWh. However, if we want to return to the mAh capacity in this case, we have: 3700 mWh / 7.4V = 500 mAh.

Ultimately, 500 mAh is the utility value for this battery, which can be compared to other batteries and accumulators of this size. If you are interested in such a more detailed comparison and tests of the battery in question, we invite you to read our test of the 9V battery.
The topic of swapping mAh/mWh units, etc., was also discussed in our article on power banks.
How imperfect the mAh unit itself is when comparing some batteries we described here.

Author: Michał Seredziński

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