Adjustable 9-30V step up/step down voltage regulator S18V20AHV


I recently purchased a few of these from a local distributor for a project and I’m running them with 11.7V to 13.3V input and wanting to regulate that to 12.2V output.

Both the load and input voltage can vary over time, the load is a halogen lamp which will vary slightly with temperature, and the source is a Li 12V battery that is somewhere between 11.7 to 13.3V, typically.

The output voltage to power the lamp must be stable 12.2V to provide a stable illumination for my application regardless of lamp temperature or battery depletion.

I connected up the 12.2V battery and the load and the output showed 8.5V. Occasionally it will show 9.1V?

Turning the adjustment screw made little difference to the output, only +/- 200mV

Are there any ideas as to why this would be?

Thanks for your help.

I’ve added some photos of my setup.

The battery is connected directly to the input. The lamp is connected to the output.

I think I may have worked out the problem. The lamp is 12V 35W which means it is around 3A.
The rating on these is 2A if I recall correctly.

This may not suit my needs in that case.

Thanks for your help.


Hello, Karl.

Thank you for posting those pictures of your setup and a good description of what is going on. Unfortunately, it does seem like your load requirements are just beyond what this regulator is able to handle, and we do not have any specific suggestions for a more powerful step-up/step-down.

If you want to confirm that your regulator is working correctly (in case you want to use it for something else in the future), you might try disconnecting the load from the output and then adjusting the potentiometer while monitoring the output voltage with your multimeter.

- Patrick