This has been answered by the above members, but I'll summarize:
The yellow ariens wire is the hand warmers.
They're wired in series, meaning their resistance adds.
The factory wiring used the alternator ac output for both the heated grips and the light, but because both of these are purely resistive they can both run on DC as well. (note: The alternator output voltage *may be different for ac and DC).
Each hand warmer is about 6 ohms; total of 12 (in series). The factory 1156 light draws around 2 amps (can't accurately remember but that's ballpark).
If you know the applied (ac or DC) voltage use Ohms Law to find your total load, and, thus, the alternator power you will need.
Have fun, good luck.
(*sold: John Deere TRS21)
Last edited by melson; 12-04-2019 at 09:56 AM.