Your laptop battery power rating can be found labelled on the battery. A typical laptop battery rating is as stated below;

**11.1V, 5.2Ah, 57Wh.**

This means that the battery supplies 11.1 volts, a current of 5.2 Ampere hours and a power of 57 Watts hour.

What does this information really tell? 5.2Ah means the battery can supply a current of 5.2A in one hour before it runs out . Or 57 Watts in one hour before it depletes provided the voltage supplied remains constant.

So let’s say your laptop power rating is 30Watts then on a battery capacity of 57Wh, your laptop will run for( 57Wh÷30W)= 1.9h or almost 2 hours. In reality it may be more or less as a result of several factors.

Both Watts hour( Wh) and Ampere hour( Ah) are measures of battery capacity. However, Wh is more reliable.

A laptop battery is usually made up of small battery cells. These battery cells are similar in shape to AA alkaline batteries but bigger..

Laptop battery usually consists of at least 3 or 4 battery cells arranged in series. To increase the laptop battery capacity, 2 or more sets of 3 or 4 battery cells in series are arranged in parallel.

The smallest laptop batteries I have come across are the 3 cell batteries. That is, consisting of 3 battery cells in series. These types of batteries are usually made for netbooks.

The standard laptop battery is made up of 6 cells. It consists of 2 sets of 3 battery cells in series, connected in parallel.

Similarly, a 9 cell laptop battery consists of 3 sets of 3 battery cells in series, connected in parallel. Of course there are laptop batteries. comprising sets of 4 battery cells in series, connected in parallel.

Laptop battery cells are connected in series and then in parallel to fulfill 2 purposes;

- To meet the voltage rating required for the laptop to operate. This condition is met when the battery cells are connected in series.
- To increase the time the laptop can run on batteries. This condition is met when sets of battery cells in series are connected in parallel.

**Decoding laptop battery power ratings**

A single battery cell can supply 3.6 or 3.7 volts and a current of over 2Ah. Since in electrical terms, power = current × volts, a battery cell can supply ( *3.6V× 2Ah = 7.2Wh*) a power of over 7.2 Wh.

Battery power ratings for your laptop are labelled on the battery.

For example assuming the battery power ratings are;

11.1V, 5.2Ah and 57Wh.

11.1V is the result of three, 3.7V battery cells in series. That is (3.7 + 3.7 +3.7)V= 11.1V. If the battery rating was 10.8V, then it implies that three 3.6V battery are connected in series, that is (3.6+3.6+3.6)V= 10.8.

5.2Ah is the result of two sets of three 3.7V batteries in series, connected in parallel. It means each of the 3.7V battery supplies a current of 2.6Ah. Even though 3cells are in series, the same 2.6Ah flows through the series connection. But because 2 sets of 3 battery cells in series are connected together in parallel, then the current supplied becomes 2× 2.6Ah = 5.2Ah.

From the calculations given above, you will realise that the laptop battery comprises 6 cells. Since power = current × volts, then each battery cell produces ( 2.6Ah×3.7V) = 9.62Wh ( when fully charged)

57Wh is the result of multiplying the power produced by one battery cell by 6.( since there are six cells in the laptop battery).

I.e. 9.62×6= 57.72Wh rounded down to 57Wh by the manufacturers.