March 7, 2019

My HQST 20 Amp charge controller

I ordered this from Amazon in January of 2019. It is smaller than I imagined (the footprint is about 3x4 inches). It has 3 pairs of screw terminals for panel, battery, and load. I had presumed that load was just a convenience, and was simply connections directly to the battery, but this is not the case. See below for an explanation.

The manual says to connect the battery first, then the panel, and finally the load.

Oddly enough, the positive connections are all common inside, and the instructions recommend grounding the positive should you choose to ground something.

The device supports 5 modes whereby the load can be controlled. Of course the load can simply be connected to the battery, bypassing the charge controller entirely. Two of the modes are intended to turn on the load a night time, essentially using the solar panel as a sunset/sunrise detector.

Inside we find 6 TO220 devices that do the serious work, these are thermally coupled to the metal backplate. Four of them appear to be paralleled and handle the panel to battery control, the other two control the load. These devices are marked HY3208A. They are N-channel enhancement mode power mosfets, rated at 80 volts. Pinout is GDS.

The processor is an STM328S005C6T6. Other parts of interest is an 8 pin package labelled 2904 SAHX. This is very likely an LM2904 dual op amp (more or less the same as the LM358).

Have any comments? Questions? Drop me a line!

Tom's notes / tom@mmto.org