# Circuit for measuring voltage and current during discharge of a battery

#### john___

Joined May 26, 2019
3
Hello dear community,

I hope I landed in the right category but I have an important question for you specialists.

I would like to build a circuit for measuring voltage and current during discharge (with different load resistances) of a battery. Of course I've already thought about that, but I'm not sure yet how to build the circuit.

Can you give me some tips please?

John

#### MrSoftware

Joined Oct 29, 2013
1,956
Are you going to manually record the values, or do you want the values logged automatically over time? Before you start designing a circuit, you first need to list your requirements in detail.

#### john___

Joined May 26, 2019
3
Are you going to manually record the values, or do you want the values logged automatically over time? Before you start designing a circuit, you first need to list your requirements in detail.
Okay, I already have two digital multimeters that I can connect to the PC to log the values.

#### crutschow

Joined Mar 14, 2008
25,991
Okay, I already have two digital multimeters that I can connect to the PC to log the values.
Than why not use those to measure the battery voltage and current?

#### john___

Joined May 26, 2019
3
Than why not use those to measure the battery voltage and current?
Thank you for your reply. Basically, I know that voltage is always measured in parallel and current in series. Unfortunately, I need a bit of help creating the circuit diagram (also in the context of the load resistors - there I would use 10, 100, 1000 ohms)

#### crutschow

Joined Mar 14, 2008
25,991
You measure the voltage directly across the battery.
You measure the current by putting the multimeter current terminals in series with the battery load.

Joined Jan 15, 2015
5,714
Thank you for your reply. Basically, I know that voltage is always measured in parallel and current in series. Unfortunately, I need a bit of help creating the circuit diagram (also in the context of the load resistors - there I would use 10, 100, 1000 ohms)
OK your circuit could look a little like this one;

The voltmeter is across your supply, a battery. Your current meter is in the current path to the load and finally you have three switchable loads. The load switch is a simple three pole switch like a wafer switch. Voltage and current will determine the actual switching. If you want data logging it depends on the data logging functions of the meters you have. That what you want? There is a number of ways to go about it,

Ron

Joined Feb 20, 2016
3,657
You may have to check the meter internal connections if you were to data log to a PC. There is a chance of a short if the PC interface in the meters are not isolated. An optical isolator may need to be added to the circuit, or a radio link.

#### Kjeldgaard

Joined Apr 7, 2016
435
If the load on the battery is a constant resistance, then only the voltage measurement is strictly needed.