Ct0517, the voltage regulator is already in your PV motor controller. You will simply connect the battery in place of the wall-powered supply. Picture this---the PV motor runs on DC and the motor speed is controlled by the exact DC voltage fed to the motor. The controller is simply a voltage regulator that allows the user to change the DC voltage slightly in order to adjust the motor speed and then maintain it at a constant speed.
The controller needs to be fed an input DC voltage to function, i.e. it needs a voltage supply somewhat higher than the regulated output voltage being fed to the motor. That "raw" DC voltage can come from a wall-powered supply that includes a small transformer to reduce the AC line voltage to a lower AC voltage and a rectifier to change the AC to DC and some capacitors to smooth out the DC voltage. That is the approach in the PV---a small wall-powered DC supply that feeds the controller. However, you can easily duplicate the function of the wall-powered supply with a battery that has about about the same raw DC voltage as the wall-powered supply. The controller circuitry is not changed when you go to a battery supply.
I don't recall the exact voltages in the PV supply and motor. I actually have a Galibier Gavia which uses a similar arrangement. In my case, the motor runs on around 5vdc so that is the approximate output voltge of the Galibier controller. I use a big battery designed for jump-starting autos, and it puts out roughly 12 to 14 volts DC which is more than enough for the controller.
It's been several years since I heard a friend's PV that was rigged up so we could switch between a battery and the stock wall-powered supply, but as I recall he used a similar battery as mine.
The current drain on the battery is infinitessimal compared to its intended use with automobiles. Consequently, the battery can go long periods of time without recharging. I typically connect mine to the charger every month or two.
