The new Lithium Ion batteries that we are now using are great for the weight savings, but they also have some drawbacks.
If you drain a Lithium Ion battery down to nothing, most on the market will not ever take a full charge again. So replace it.
Here’s some general rules on any type of battery.
A completely dead battery should take at least 35-45 hours or more with (0.75 amps), and 20-30 (1.25 amps).
A battery charger cannot begin to charge a fully depleted battery. They need to sense a certain amount of voltage before they can function.. So you must hook another battery up to the dead battery before charging can start.
If you try to charge a dead battery having a voltage below 3 Volts, most battery chargers will not start.
Two kinds of chargers – Float and Trickle
The difference between a float and trickle charger is that a float charger will only turn on and charge your battery when it has self-discharged below a certain level, whereas a trickle charger continuously emits a small current of electricity regardless of the charge level or even if it’s full. So basically never use a trickle charger.
You can use any charger to charge Li-ion batteries, provided it has the right voltage(Which will depend on the battery you have)
Another issue to address at another time is the voltage rectifier on the motor.
My personnel choice of batteries is the WPC, great recovery, seems to last longer than most.