If the battery already has acid in it, then you cannot drain it. To keep the battery in good condition you will need to put a battery charger on it at least once a month, better to charge it every two weeks. Use a trickle charger or taper rate charger and let it cherge until the battery is fully charged (with low output battery chargers it can take 12-24 hours to fully charge the battery - the slower the better to prevent overheating the battery). With a taper rate battery charger look for the charge rate to go down to zero or, better, check with a volt/ohm meter and look for 13.2 to 13.5 volts.

Good Luck!
Tom

__________________
America: Land of the Free!

1977 300D: 300,000+ miles

American Honda: Factory Trained Technician & Honor Grad.
Formerly:
Shop Foreman;
Technical Advisor to Am. Honda;
Supervisor of Maintenance largest tree care co. in US for offices in Tex.