My kid has a honda 300ex. recently tuned up. really good shape for a 2005. bought it 3 years ago so not sure how old battery is. stalled while riding it other day. he was in 4th gear on trails. wouldn't start. like the battery was bad and didn't have enough juice to turn over the engine. charged the battery and next day, same thing. can a bad battery stall out the quad while riding it ?

 

The alternator should make enough power to keep the engine running even with the battery disconnected. I guess a dead shorted battery may take all the power but not on two different batteries. So your alternator or voltage reg probably has failed. For it to run the second battery down that fast you may have a "drain" all the time, follow the tests I recommended for someone else this week. https://atvconnection.com/forums/hon...er-source.html