I have a little project I'm trying to get figured out, and I need a little help. I have a snowmobile, which has no battery (pull start). It does have a stator / regulator-rectifier that powers all the lights, gauges at ~14 volts. I installed another set of gauges that are electronic (exhaust gas temperature gauges). The problem is that when the engine is shut off, or the RPMs get too low for the system to put out full voltage, the EGT gauges shut off. My plan was to install a small (0.8 or1.2 amp/hour) 12v battery, with a diode so the system will charge it, but the diode will prevent the battery from draining back through the electrical system (Charging system -> Diode -> Battery -> EGT Gauges in the + side). That all seems to be OK, ,, but, , the machine's charging system at ~40watts will charge that small battery too quickly, as that sized battery is reccomended to be charged at around 4-6 watts. It is my understanding that a resistor could be used to limit the current to the 0.3 - 0.5 amps it should be limited to, but I don't know a) if a resistor will really work in this capacity, or b) how to calculate the ohms of said resistor. Any help will be appreciated. Thanks, Greg.