Automated Lead Acid Battery Capacity Tester

[sa87]

I need to design a battery test bench to perform capacity test for starting type lead acid batteries.
Full charged lead acid battery 12.6V and do the constant current discharge until 10.5±0.05v
According to the battery capacity discharging constant current should be able to change and these data should be able to take to computer. Timer should be included and also the voltage cutoff to stop the discharge at 10.5±0.05V. This should be automated one.
I was thinking about to do this using a switching dc load which keep the constant current through out the test when the battery voltage change. If somebody can give me a suitable switching load design to perform this it may be very helpful. Thanx

 

[duke37]

What is the effect of discharging a battery intermittently? Even if the mean current is correct, the pulsing current with a switching design may affect the results.

You could use a main resistor to give the current you need at the highest voltage and add resistors in parallel as the voltage reduces. This could be done in discrete steps or with a linear regulator.

 

[BobK]

What is the range of currents you require? An LM317 can make a good constant current source of up to 1 A with a range of 10.5 to 12.6 Volts input. But I suspect you are talking about higher currents than that, no? Adding external pass transistors can up the current output.

Bob

 

[sa87]

What is the range of currents you require? An LM317 can make a good constant current source of up to 1 A with a range of 10.5 to 12.6 Volts input. But I suspect you are talking about higher currents than that, no? Adding external pass transistors can up the current output.

LM317 is a good idea. But I got a idae about doing this using LM324 opam with a MOSFET switch . Can somebody help me to design this

 

[BobK]

It is hard to help you if you won't tell us what range of current you need.

Bob