How to understand the different values of mAh capacity in the specification of a rechargeable battery?

We have already described the fact that the usable capacity can vary depending on the application, especially in the case of disposable batteries.

To conclude this topic, it can be stated that in the case of disposable alkaline batteries, it would be nothing special if the batteries had e.g. 3 mAh capacity values – for low loads, e.g. 5 mA, moderate loads, e.g. 100 mA, or high loads – e.g. 1000 mA. The value of the capacity given at the lowest load would often be even several times higher than that obtained at the highest load – this is completely normal for this type of battery.

Another special case is power banks, where we explained why the capacity of built-in rechargeable batteries will always be different (clearly higher) than the usable capacity from the USB outputs.

However, some doubts may be raised by giving two capacity values, e.g. for Ni-MH AA/AAA batteries, or Li-ion 18650, 21700, etc. These batteries behave repeatably in typical applications and obtain similar capacities at low as well as moderate loads.

Despite this, many manufacturers still use the concepts of minimum, typical, maximum, and design capacity.

1. Typical/minimum/rated capacity of rechargeable or rechargeable battery in mAh

This term currently means the value of the capacity given in accordance with the provisions of the EU Regulation 1103/2010, which came into force on 30.05.2012. In short, it means the obtained capacitance result according to a specific procedure, the PN/EN/IEC technical standard.

According to this standard, the battery should primarily have one binding capacity specified.

Using Ni-MH batteries as an example, the standard assumes that a freshly manufactured (not older than 2 months) battery is discharged with a current constituting 20% (0.2C) of its capacity value to the voltage level of 1.0V. On the entire test group, production batch, pieces with a lower than declared capacity value are practically unacceptable.

As a rule, this result can be compared between different rechargeable batteries (from different manufacturers) with the same capacity – because we can be sure that the test conditions were almost identical for them.

The formal conditions of such tests are precisely defined, so all major battery manufacturers, in order to be sure that all batteries meet the minimum requirements, produce their batteries with an appropriate capacity reserve – at least by 3-5% – these higher values can be called maximum or design capacities.

Currently, there is an obligation to provide the minimum/typical/rated capacity for almost all rechargeable batteries – it should be the only value with the mAh/Ah unit written directly on the cell.

minimum capacity=typical capacity=rated capacity=nominal capacity

If, in addition to the indicated mAh capacity, we have other values on the battery or its packaging, it can only be the name of the series or just the determination of the maximum designed capacity of such a battery.

2. Maximum capacity/design of rechargeable battery or battery in mAh

In the case of major / serious manufacturers, this is still a real value that can be obtained by the user. First of all, as we wrote, it is nothing special to produce rechargeable batteries with a certain technological reserve – thanks to this, a large part of rechargeable batteries will reach values higher than the minimum even in a formal, standardized test.

Before the provisions of EU Regulation 1103/2010 came into force, there was no formal obligation on the market to indicate the tonnage in a strictly defined manner. It was possible, for example, to discharge the battery with a lower current, to a lower voltage, or at a higher ambient temperature – all this affected the possibility of obtaining higher capacity results.

Sometimes the value of the maximum capacity can be abused and have nothing to do with reality – if, for example, on the market we find a 18650 battery with a capacity of 10000 mAh or 12000 mAh, where at the date of writing this article the technological limit is about 3500 mAh, we can be sure that we are dealing with a fake or a scam.

Finally, when interpreting the values of capacity expressed in milliampere-hours of the mAh, we should remember a few rules:

• in the case of disposable batteries, this is a very approximate value and has no comparative value,
• in the case of rechargeable batteries, if we want to maintain a comparative value between different batteries, from different manufacturers, pay attention to the minimum/typical/rated capacities – only these can be safely compared,
• the maximum capacity is usually still the real value that we can count on when using a given battery/battery – usually these values are slightly higher than the minimum/typical values, and so, for example, when buying a rechargeable battery with a design capacity of 1000 mAh and a minimum/typical capacity of 950 mAh, we can assume that the vast majority of rechargeable batteries will reach capacities in the range of 950-1000 mAh, with few exceptions beyond this scope,
• When we find rechargeable batteries with seemingly unrivaled, very high capacity and at the same time low price, let's check their exact technical data, whether there is a typical/minimum capacity given in accordance with the regulations – the appropriate PN/EN/IEC standard.

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