Tim, I personally would never plow when the battery is at 8-9v. I would stop plow and idle or drive around a bit until it get back to 14v then plow again. Myself, I would never run anything lower than 12v, maybe 11v but that is as far as I am risking to go. For snowplowing, I recommend you to go with yellow top. It can be cycled over again and again without going bad. If you don't have auxiliary battery, then it would be a good idea to get one if your budget allow it.