The short answer: You are fine with your plan for charging the AccuVote power supply batteries.
The longer definitive answer is this:
Visible Light AccuVote units use a trickle current to charge their power supply battery. This type of charging should not harm the battery in any way. To charge an AccuVote power supply battery, the AccuVote must be plugged into an AC outlet, with the power switch turned ON, and be without a "POWER FAIL" message flashing on the LCD display. After charging, turn the AccuVote unit OFF prior to disconnecting the power cord. This procedure will prevent accidentally discharging a battery by leaving an AccuVote turned ON after pulling the power cord.
Time to Charge
Note: A sealed lead acid battery sitting on a shelf (at room temperature) loses about 3% of its charge per month. AccuVote batteries should always be charged before and after an election.
Note: Completely discharging a sealed lead acid battery can damage it to the point that it may not hold a charge. After charging, always run a "battery load test" to ensure the battery is holding its charge. After a (brief) successful load test, you should top up the charge for 3 to 4 hours. See your AccuVote Operator's Guide for details on testing a charged power supply battery.
If you have any other questions, please contact me.
Ian S. Piper
Global Election Systems, Inc.