Hamid,

 

My procedure is to buy a battery every year at condition inspection time.  I have two, so I will always be flying with good reserve power.

 

When I discovered my battery was drained and wouldn't recharge I was preparing for a trip to the west coast.  I went anyway.  I have 2 25ah batteries and two alternators.  A VFR trip with only one battery and only two alternators seems plenty safe to me.  I flew my first 15 years with one battery and one alternator.  The only thing bad about the trip was my audio system is hooked up to the bad battery, no tunes for 5 hours each way!

 

Mike