A splash screen shows up as we
start that says set voltage to 0 and then press Start for help.

This project is a simple use of an Arduino Nano to make the smarts for a simple but useful test tool.
Several common small battery connectors or connector for a cell phone charging battery are attached in this picture.    This tester can support 20Amp load currents or more at 40V.

To start a capacity test the user adjusts a test cutoff volatage on display, 3.54 volts here.

The user presses 'Start' and a power MosFet connects the load to the battery, green led ON.
While the test runs the runtime minutes,  TMin shows up and battery voltage slowly drops.

The 'Loading' led shows and the 'Running' led blinks as the test progresses.
When the battery voltage drops below cutoff (Cov) for a couple seconds, test stops.
User can come back and see the test has stopped and note the minutes it ran.

I plan on showing AmpHours as the test runs but have not added that code yet.
The Current Load Tester has two connections to hook up a battery or power supply of your choice to be tested.  Very high current connections are used along with a High Current MosFet 'switch' that is controlled by an embedded microprocessor depending on the mode.

There is a 1.3" OLED display to assist in setup and test status or even a help menu.

The Current Load Tester works in these two modes:
- Capacity Test:  Here the load is always on and a timer is shown. Load is off when the voltage on the battery drops below a threshold set by the knob. 
- Pulsed Load:    The load is connected then disconnected to the battery about once per seconds.  The width of the time for the connection is set by the knob. 

Running a Capacity load test:

Below is shown a capacity test in progress on a LiIon RC Toy Cell and a 10 ohm load.

The tester reads the battery voltage as 'BatV' and will automatically stops a load test at the knob defined cutoff voltage (Cov).  Stopping the test prevents bringing the battery below its lowest safe discharge level which can and will damage a battery. 
Pulsed Load Test For A Battery Or Power Supply:

User sets the tester into 'Pulsed' mode with a switch, I don't have picture of this new switch yet but I have it all working.  The voltage of the battery under test is shown as BatV.   The user selects the lenght of the pulsed load periods.  

The user presses 'Start' and a power MosFet connects the load to the battery for the brief pulse time that has been set.  It does this about once or twice a second.

The user would setup an oscilloscope to show the dropouts and evaluate performance.

The pulses happen about every few seconds with no control for the frequency.
A Splash Screen Shows At Startup
Current Tester for Battery Or Power Supply Tests
Mark-World - Tech Projects To Amuse The Curious
Current Load Tester