So I just wanted to give a quick update on the project status.
I ran with the 48v system but since these batteries have a nominal voltage of 1.2, and with 12 cells, they have a nominal pack voltage of 14.4Volts. With 3 packs, that makes 43.2V nominal. I was very happy to be able to throw snow and drive on that voltage.
Now with the 48V controller, there's not much for documentation. I'm assuming since the voltage is in a multiple of 12, they allow for the charged voltage of lead acid batteries. If that's the case, then the controller could potentially handle 54V fully charged (13.5V max per battery). With that in mind, I wasn't sure if 4x12 cell packs would burn out the controller at closer to 57V. I realized the original small engine never stops spinning, so why should my motor?
I've taken out the speed controller and replaced it with a large battery contactor (high current relay) from a salvaged Hybrid Prius battery. This contactor works great! I will add a 12V regulator for onboard headlights and to control the relay. This'll just require that I disengage the clutch before starting up the motor. This should lower the initial starting current of the motor.
I've spent an enormous amount of time testing each battery pack, and bottom balancing them before combining them into their final configuration.