It more than likely has a dead cell and needs replacing. That is assuming the charging system on the ATV is working properly.
you charge a atv battery at 2 amps or lower
As long as the ATV is wired 12 volt, not 6.
I am assuming you mean with the auto engine running. Yes, that is possible but you are putting a strain on the alternator of the car. An alternator is not designed to charge a dead battery. It is designed to keep a charged battery fully charged. as long as the ATV battery is the same voltage as the car battery, usually 12 volts, you can charge it, or jump start the atv and let it charge the battery itself.
either plug it in to a charger or take off the alarm, it drains the battery
If you keep the key on your ATV on for two days, the battery will probably go dead and need a charge or jump start.
Your battery will lose charge faster.
No they lose some of its power over time. it depends on the type of the battery. rechargeable lose more of there charge that normal battery's.
Remove it and hook it up to a battery charger. If you don't have a battery charger, you can take it to Autozone and they will charge it for free. Just be careful handling the battery because battery acid can cause serious injuries and damage to property.
charge the battery, change the battery, use the back up start either a pull start or kick start.
Yes, if your car battery is the same voltage as the ATV battery.
Yes, you can use a twelve volt car battery charger. Be sure to set it on low.
Because it has to be replaced.