The only thing a PWM will do is control the eletricity going to the plates. The reason folks choose to experiment with them is that it can help (in some cases) control temperature.

You may notice that after a while of powering you cell on the bench or in your car, the water temp rises and so does the gas production..After you reach a certain temp and amperage, production begins to drop.

By regulating the electricity, it will help you control run away temps, especially in smaller generators. This comes at the cost of lost gas production though.

There is a necessary balance of things such as electrolyte mixture....volume of electrolyte in the generator....the ammount of electricty in the plates....the water temp............and probably a few other things I have yet to learn about, but what I have learned so far is that the PWM will only drop gas production and temperature as a result.

IMHO, if you have the available space, use a larger generator cell to hold more electrolyte. It will help with the temp without offsetting the necessary balance of things.