In my early years I worked in a gas station. Lost count of the number of people who would have cars towed in and tell me "Needs a new starter", "needs a new battery", etc.
I also lost count of the number of times I would merely remove the battery cables, scrape both the post and inside of clamp with my trusty pocket knife, re-attach, then hit the key ----Vrooom, engine started.
Got a call from my Mother one time. Her husband was in the hospital for surgery and she had their MH home parked at the hospital. She couldn't start the generator and lights went off when she tried.
Same thing. Battery cables were so corroded between inside of clamp and post it was amazing that the lights even worked.
Second most common issue from my early service station days? The ground cable, where attached to the engine, was loose as a goose. I began to wonder if anyone had ever heard of lock washers.
Anytime an electrical connection gets hot and then cools, like a ground cable attached to an engine block, or battery terminals that are subjected to several hundred amp currents for short periods of time, REGULAR maintenance is a must. Clean and tighten. Amazing how much more electricity batteries will hold too as any resistance at the connections will signal the charger that they are full, prematurely.
Lastly, a good test of battery and ground connections is to hold one lead of a multimeter to the center post of a battery connection and the other to the connector itself. Remove spark plug wire and crank engine. Measure voltage drop across the connection. It should be less than .1 volt. Repeat at ground connection as well as solenoid connection. People might be shocked at how much voltage loss their conndections have when cranking the genset due to improper (or total lack of) maintenance.
Life is full of choices. I choose to have fun!:)