This program controls "Electronic Load" devices XY-FZ25 and XY-FZ35, sold on different webshops, mainly from Asia. Most of them provide detailed instruction manuals as well. In folder Doc you find some specs.

A programmable electronic load emulates DC or AC resistance loads required to perform functional tests on batteries, all sorts of power supplies, solar cells, technical equipment, etc. There are many other useful scenarios. In the simplest case an electronic load just sinks current (absorbes power). The amount of current can be set and the load tries to keep it stable even when the applied voltage changes.

The XY-FZ25 is limited to 4A/25W and the XY-FZ35 to 5A/35W. That doesn't sound much but really is enough for most cases. I use the combination program + electronic load mainly for battery/accumulator discharge tests and solar power cell tests every now and then.

The program "Electronic Load" in folder Program does display live readings in a chart. Furthermore it can:

• save charts as data file (.eld), bitmap file (*.bmp) or csv file (*.csv)
• print charts
• load previously saved charts (*.eld data files), which gives you the easy ability to compare the various test results later on

If you associate *.eld files with this program you only need to double click them to see saved charts.

For more pics have a look at folder Doc. The program was tested and runs on Win8.1/Win10/Win11.

You find some real world charts (*.eld) in folder Program. Load them into the program and have a look at them.

The program lets you set various operational parameters. The most important of course is the

• Maximum Load Current

Additionally the load will monitor various definable parameters and trigger an alarm plus turn itself off if required:

• LVP...Low Voltage Protection: When the load voltage drops below a set limit. This is important for discharge tests in order to protect the accumulator/battery.
• OAH...Maximum Discharge Capacity: When the load reaches a defined accumulated discharge capacity limit (in Ah). This feature too is for protecting the accumulator/battery when doing discharge tests.
• OHP...Maximum Discharge Time: When the runtime reaches a set timespan. Important for tests that need to run for hours or even days.

Changing those values can be done either via the programs menu (Settings) or by clicking with the mouse on the value in the main dialog. The respective dialog will then show up.

Mouse clicks on the left chart axis will change its scale. This can also be done via menu of course.

Don't forget to set the correct hardware version of the device before controlling it (Settings->Hardware Version->25W/35W) !

Depending on your Windows architecture copy the 32bit or 64bit version of the executable into a program folder and that's basically it.

In case you get a windows error message trying to run the program (like "mfc14xx.dll missing" or similar) depending on your Windows installation you additionally need to install the Microsoft Visual C++ Redistributables 2022 (x86/x64) or higher. Momentarily (02/2024) they are available from here.

The devices have different self protection mechanisms built in and will turn off when triggered:

• OVP...Over Voltage Protection: When the load voltage gets higher than the set OVP voltage limit.
• OCP...Over Current Protection: When the load current gets higher than the set OCP current limit.
• OPP...Over Power Protection: When the power it absorbes gets greater than the set OPP power limit.

Pressing CTRL+L will retrieve the actual protection limits from the device and show them in the program window (top left section), provided the device is properly connected.

If reading limits is not possible a warning is displayed. Same when sending limits to the device hasn't been successful or the device didn't answer as expected. In all error cases the values in section "Protection Limits" will stay at zero.

Please note:
Some alarms (OPP, OAH, OHP) can't be cleared via serial communication. In such cases the On/Off Button on the device itself must be pressed to end the alarm and get the device operational again. Message Boxes will tell you if that's the case.

The devices provide a possibility to communicate via serial port (9600,8,N,1) with TTL-level (3.3V !). They accept operating instructions and send status messages if requested.

This program uses this option to control the devices. For that you only need a cheap USB-TTL converter module (mostly with IC CP210x/CH340/FTDI232) between your Laptop/PC and device.

• 2019/05: V1.0.0, Initial version, built with MS Visual Studio 2019.
• 2019/10: V1.0.5, Some bugfixing to catch all alarms properly.
• 2022/02: V1.1.0, Export chart to *.csv added. 7-digit display for load status added. VS2022.
• 2022/03: V1.2.0, Error messages improved.
• 2024/02: V1.3.1, A nasty 2-digit COM error fixed. Load current can now be set to 0.00A which is helpful for monitoring only. Option to display LVP voltage in chart added. Horizontal scrolling on event list box activated.
• 2024/02: V1.3.2, If the voltage drops from above LVP straight down to 0.00V then the load unexpectedly stays on and does not report a LVP alarm. This is now detected and the load is then instructed to switch off. This scenario can happen if the battery has been disconnected manually or the internal battery BMS turned the battery output off before the decreasing battery voltage hit the set LVP level.
• 2024/03: V1.4.0, New settings option will request the system to stay awake and not enter sleep mode while load is switched ON. This will not work on all systems though, esp. not on systems with active "modern standby" feature (e.g. newer laptops) while running on battery. You actually have to try it out on your particular machine before you can rely on it.

If you run into trouble with this program or have suggestions how to improve it, feel free to contact me.