Battery capacity is the amount of time the battery can power the connected load. Typically, capacity is measured in ampere-hours, and for small batteries, in milliampere-hours.
Instructions
Step 1
The amount of electricity (charge) in a battery is called capacity. The charge is measured in Pendants, 1 Pendant is equal to 1 Ampere x 1 second. In order to find out the capacity of the battery, charge it completely, and then discharge it with a given current I and measure the time T, during which a complete discharge will occur. Multiply the time (T) by the current (I), and you get Q - the capacity of the battery.
Step 2
To check, fully charge the battery and connect it to this device. Set the clock to the indicator and turn on Start. Now the relay should close contacts 4-5, as well as 5-6, and the battery begins to discharge through the resistor R, voltage is applied to the clock. The voltage on the battery itself and on the resistor begins to slowly decrease, when it drops to 1V on the resistor, the relay opens the contacts, the discharge stops, and the clock stops.
Step 3
When the battery is discharged, the control current passing through contacts 1-2 of the relay drops from 8 to 2 mA. If the control current is 3 mA, then the resistance of contacts 4-5 and 5-6 is less than 0.04 ohms (the value is low enough not to be taken into account when measuring the current). If you need a discharge current of 1A, then use a resistor R = 1.2 Ohm.
Step 4
After the discharge stops, the voltage on the battery begins to rise to 1.1-1.2 V, this is due to the internal resistance of the cell. Take into account the fact that the capacity of a newly charged battery will be higher, because after some time, part of the charge is lost through self-discharge. In order to calculate the amount of self-discharge, measure the capacity immediately after charging, and then about a week after that. Some batteries may self-discharge 10% per week or more.
Step 5
If you are using this circuit, try reducing the resistance of the battery contacts and connectors. If the current has a strength of 0.5-1 A, you can get a not very high measurement accuracy (you will lose 0.1 V or more on the contacts). Also, loss of accuracy can be caused by a steel spring, which is used in some battery holders, so shunt it and other contacts made of steel using a copper wire.
