# Discharge constant 2A-3A current from a battery

I am supposed to drain a constant current of 2A or 3A from a battery (most probably a NiMH battery). What could be a possible way to do that ? Purpose of doing it is to calculate the battery's Energy (using a micro controller) for the discharging cycle, while keeping its current constant.

Thankyou,

EDITED

What if i am using a buck-boost converter with a micro-controller to charge my battery and then discharge it? (Buck topology will work during the charging cycle and boost topology during the discharging cycle.) Would the following idea be practical ?

I mean if i choose a resistor (lets say for discharging 15V battery @ 20A) and connect it to my circuit given above during the discharging (also disconnecting my circuit from the main power supply), would i be able to drain a constant current for my test purpose ? I dont know exactly how the boost topology will exactly work during the discharging cycle. But looking at the circuit, will i be able to draw a constant current out of my battery using PWM from my micro-controller ? And, would placing a constant value resistor for the discharging be a correct method to do (in this case) ? Please help me if i am thinking totally wrong. Please tell me would my idea be practical or i am just being silly here. (sensors and resistors which will be used to measure the voltage & current supplied to and drained from the battery are yet not drawn here by me) Thankyou.

• A current sink? Commented Feb 24, 2015 at 12:35
• Search for eg constant current load Commented Feb 24, 2015 at 12:49
• Stack Exchange EE is a good place to look :-) - eg se Abdullah's answer here Commented Feb 24, 2015 at 12:52
• You need to think about what tolerances you need to hold. If, for instance, you need to monitor a battery from 1.2 to 1.1 volts (terminating the test when the battery voltage drops below 1.1), and the current can vary by +/- 5%, a simple resistor will do the job. If you need the current specified within +/- 1%, that's a different story. Commented Feb 24, 2015 at 14:28