My son has a 50 cc Eton 2 stroke quad. I can leave it on the battery tender or charger all night and when I try to start it, it cranks about one time then just clicks. I assumed it was dead. A couple weeks ago I jump started it and he road for a while and it shut off (ended up being out of gas) anyway long story short when he has been riding for a while it will crank and crank and crank but once it sits over night (even when showing fully charged) the battery won’t crank it over. I have had two separate chargers on it with same result. Is this likely the battery or something else that could cause this?