the reason why the battery meter drops quickly and suddenly with lithium batteries is because they have different discharge characteristics than regular alkaline batteries.
with alkaline batteries, as you use them, the voltage slowly drops until there is no more juice left. so your deck's battery meter is looking at the voltage of the batteries.
with lithium batteries, as you use them, the voltage remains constant (or much more constant than alkalines) throughout their entire life. so your deck doesn't see a voltage drop and assumes full battery power. and then they die.
hope that explains it.
- Jason