# Special Parameters of Lead Battery Contents

There are some special battery parameters not easy to figure out instantly. Here for your better understanding, the following is a summary of some.

## Nominal Voltage

Voltage is literally the output voltage of the battery. But the battery voltage does not remain the same at a fixed value. Due to residual energy or other external environmental differences, the battery voltage will vary in a certain range.

Generally, the nominal voltage is a reference voltage value, not an average value. For example, a single cell of lead-acid battery is rated at 2V, while a single cell of LiFePO4 battery is 3.2V.

Multiple cells are connected in series to make up our common 12V battery, 12V lead-acid battery, and 12V LiFePO4 battery (the actual nominal voltage is 12.8V).

## Capacity and Hour Rate

Capacity is measured in Ah or mAh (for low-capacity cylindrical batteries or cell phone batteries, etc.). It is the multiplication of current unit Ampere and time unit h(hour). The meaning is how much current can be discharged for how many hours.

Commonly we would think that, since the total energy of the battery is certain, the multiplication of the current and the number of hours must be the same. In fact, it is not.

The higher the current is, the smaller the multiplication is. Or we can say that the higher the current, the less energy the battery can release.

This results in a precondition, the hour rate. Capacity is generally defined as the capacity based on a certain hour-rate.

For example, a 12V100Ah lead-acid battery, based on a 10 hour-rate, means that 10A current can be discharged for 10 hours. And it can’t be discharged for 1 hour at 100A. Actually, for 100A discharge, the discharge time is around 35 minutes.

You can see from the table below, if for 20 hour-rate, 5.36A can be discharged for 20 hours, which means the actual capacity is 107.2Ah C20. And if for 1 hour discharge, the current is 55.9A if we set 1.80V to the end voltage (10.80V for 12V battery).