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.
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" 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. 

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.
Current Tester for Battery Or Power Supply Tests
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 user uses the top Adjust control to set the voltage threshold where once the battery droops to that level the test will stop and the number of minutes it ran remains shown.

The tester reads the battery voltage as 'BatV' as the test progresses 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.  The adjustment on the right side (ran out of front panel space) will set the time between tests and allows battery to settle back to stability after a pulsed load.   The display shows 'Perd' for period in millisec up to 10 sec and here it shows 5140milliseconds in the picture.
User sets a duty cycle with top adjustment control for 1% up to 100% and the pulse width shows on the display as PulW or 537milliSec in this example picture.
User hits 'Act' (activate) to start the test and when battery load is applied the red led shines.

The voltage of the unloaded battery under test is shown as BatV and is the voltage just prior to another pulse.   

The 'BPul' reading is the voltage of the battery near the end of the active loaded pulse. 

For details on how voltage drops a user can use an  oscilloscope to show the dropouts and evaluate performance.
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Current Load Tester