You can use 3 x 1.5 volt batteries in series as a power supply. The setting is based on a percentage of the input voltage so the actual input voltage is not critical.
What I had done on my SRX was to build a harness that had pigtails on the TPS wiring harness so I could set it from the sleds input voltage when it was idling.
Ok still not sure about how to get input voltage lpl. I did try the 3 1.5 v batteries in series but i get same voltage as what the 3 1.5 volt batteries add up to. Which is 4.8 lol