Peter- after having my batteries on the BatteryMinder for a month and taking it off for a few days my batteries read 12.76-12.9 volts - they are fully charged. I then put them back on the BatteryMinder and will take them off as I need them.
Car54 - I paid $270 CDN for my Factory Mercedes battery - leaving it on the charger for 7 months is still cheaper than buying a new one. Also at the same time my Mercedes battery is being maintained, so is my garden tractor battery and my outboard motor battery - all on the same BatteryMinder. My savings is definately worth the expense. The 10 cent figure was from their website. Every year I have had to buy a new garden tractor battery and every 2 years a new outboard motor battery because they are not used most of the year. In your case it may not be economical to use - but in my case it is. Cheers