Hey Clark, here's some info I found helpful when I asked the same question in my thread for my '71 Case 444.
Follow these two links for some additional info the guys gave me when I was up against the same issue: http://gardentractor...actor/?p=269022 and http://gardentractor...actor/?p=269537.
Here's a snippet of what you'll find by following the above links.
"QUESTION: I don't run anything other then the headlights, they are upgraded bulbs. I don't know how much draw these tractors were designed to take before the charging system can't keep up any longer.
ANSWER: The formula for that is 12 watts=1amp at 12 volts take the amps of generator times 12 gives the watt output keep at least 50 watts free to charge battery .
QUESTION: Ok, so gopher, you're going to have to help me cause I'm slow on the uptake with all this electrical gibberish. If I have two 18.4 watt headlight bulbs and two 27 watt bulbs (one for my dash light and the other for m backup light) am I still within the 50 watt free zone to charge my battery? I don't run my reverse light all the time but if I did would I still be in the clear?
If my starter/generator puts out about 15 amps then multiplying that by 12 would bring me to 180 watts of output. Adding the wattage on my lights that brings me to an approximate total of 91 watts. This leaves me approximately 90 watts free to charge the battery. How did I do? Thanks.
ANSWER: That is correct I'm not sure how low you can have the charge watt I have 50 and know it works to keep battery charged.If you want to add more I would not go under 30 watts for keeping your battery charged. I'm assuming that would be like a 2 amp trickle charger."
Edited by Moosetales, October 23, 2013 - 04:04 PM.