How to choose the right size of battery

As mentioned earlier, batteries come in all shapes and size, from types no larger than a shirt button, to a battery system filling an entire room.

To find the size of battery you require you generally need two pieces of information, battery load and back-up times. (Note: other factors may also have an effect).

Battery Load

Whether you power lights, motors, electronic equipment or a toy vehicle you equipment will draw a load in AMPS. If this is unknown then the equipment will have a rating expressed in Watts which may simply be converted to Amps by dividing the value by the normal voltage of the system.

Back-up Time

This is the time you require the battery to support the load described above and is often called Autonomy or discharge time.

Example: To power a cordless electric tool for a total of 3.0 hours before recharging. With these two pieces of information use our selection graph to plot an intersection point from which you will determine a required size or capacity in Amp. hours (Ah).

Our figure has been rationalized into rounded figures of capacity. If your intersection point falls between two lines choose the next highest value.

Always choose a suitable sized battery from the ranges appropriate to your application.

You may notice that the chosen capacity in Amp hours is often higher than the Value of Amps x Hours used, in our example using 10AMPS x 3 HRS = 30Ah and the chosen option being 38 Ah. This is because the capacity ö¿cAöÑ of each NP battery is stated at the 20 hour discharge rate. You will only get full capacity if discharged over that length of time.