Electrical – How to Run a 230V 50hz tool on 100V 60hz

This leaflet just contains some general information concerning the product. The only thing relevant to installation is in point 5 (labeled 五).

Basically, the user is told to connect what are literally labeled as the "fire wire" and "null wire" (火线 and 零线) -which I interpret as respectively the red and the black wires- to an AC supply of 180 to 250V, 50 to 60Hz frequency, where the device should happily consume less than 60W of power.

This agrees quite well with what is on the bottom of the box.

This device does not need an earth connection, since the enclosure is plastic. Earthing is used when the container is metal, and the user could receive a shock if a live wire was touching the interior.

In addition, please note the timing seems to be able to be graduated, from 50 +/- 20 seconds.

Since you have an old car battery, the cost of damaging it by overcharging isn't much ($40?) and that would only happen if it got a lot of sun over weeks. A small home solar system might have thousands of dollars of batteries, so standard practice has long been for those to always have charge controllers.

For small systems the cost of a charge controller used to be significant so it was common to forego it in favor of simplicity. However, there are now very - inexpensive - controllers which no longer as easily justify the old practice.

If you can afford an additional $25, you might as well do it right. Also, it would come with instructions on what to do.