manual says leave battery in charger for 1 hour after light goes off for Full charge
Agree, I believe the chargers are somewhat similar to those used for serious RC models which uses Lithium Polymer for power.
These chargers uses a CC/CV (Constant Current/Constant Voltage) algorithm to achieve full charge of the batteries, they'll charge at a constant current till the battery reaches about 95% of it's capacity(light goes off) before switching to constant voltage mode for topping up the battery.
The really good ones would have a balancer function to ensure the individual cells inside have equal voltage.