Warm ground wire at batteries, no start Gen.

I had this problem with my generator not starting a while back. I cleaned and tighten the connections I could read 12.5 v back to the starter but still no start. I backed my tow car up and jumper ed to the starter. It stared right up. Perplexed, I started to trace the wire from the genset to the battery pulling on the wire as I worked my way to the house batteries what I found was that as I wiggled and pulled on the cable it came out of the terminal. The inside was corroded(green) about 2 inches inside the cable while the terminal that was attached the battery was clean and tight. After stripping the plastic back and re crimping, soldering and applying heat shrink all was well again. I learned that just because you have proper voltage that does not mean that you have enough amps getting through to do the job.