all i have to say, is if you ever leave the mags on and an A&P comes to work on your plane, you will get an ear full. I always check before turning the prop but there is always the chance of me forgetting to check (swiss cheese model). This could easily result in my death, especially if someone turned the engine off by the mags.

and yes, the above posters are correct. the mags have absolutely, positively nothing to do with the battery or electrical system. they are an independent system for a reason.