Onan generator problem

We had another case that sounds like yours a week or two ago. The battery was a little low. I forget if the batt had to be taken someplace to be charged then brought back, or charged in place. I mention that because the take-out-to-charge route probably would also result in terminals checked and cleaned. Did you remember to "prime" the carb with fuel by holding the rocker switch to OFF before cranking? I end up doing ours at least twice, even in our warmer weather. You won't flood it doing that, provided the carb's Float Needle and Seat are OK. You'll just know the gas is right there, and hopefully reduce cranking time.