Current source for a Capacimeter

[Sami issam]

hey , i just have this project of making a capacimeter for calculating the capacities of batteries in Ah from 9 V to 12 V , my idea is to charge the battery , and then discharge it with a constant current by connecting a current source with the battery in the same branch , and mesuring the batterie's tension and counting the time using a PIC microcontroller ,the current value i need is about 1 A . this is the synoptic (below) and i'm just looking for some good schematics for my current source that fits my circuit .

 

[(*steve*)]

Look at image 3.1 here.

The linear constant current driver that is used for a LED in this case can be used as a constant current load on a battery.

You can include the LED if you want to, or select a resistor suited to the discharge voltage of the battery, or remove it completely.

Make sure that the transistor carrying the load is appropriately heatsinked.

 

[WHONOES]

Look at image 3.1 here.

The linear constant current driver that is used for a LED in this case can be used as a constant current load on a battery.

You can include the LED if you want to, or select a resistor suited to the discharge voltage of the battery, or remove it completely.

Make sure that the transistor carrying the load is appropriately heatsinked.

I agree with Steve. I have used the circuits shown in 3.1 and 3.4 hundreds of times down the years. They both work well.

 

[BobK]

The capacity of a battery varies with the discharge rate, so you should allow for a variable current. Also, what are you going to ise for the end criterion?

Bob