[Ptero]

Yeow! There is no way it takes this much energy to charge those batteries.
Let's see, optimally you would want this:

Muscle power ==> rotation ==> transmission (frictionless) ==> DC generator (correct rpm) ==> DC to battery (requires regulation circuitry for correct secondary battery charge)

But we have this:

Muscle power ==> rotation ==> transmission (lots of friction) ==> DC PM generator ==> automotive battery (charging) ==> AC inverter ==> transformer to DC ==> DC to secondary battery (properly regulated)

My estimate is that for every 10 power strokes, 9 are wasted. Compare your output to an emergency battery or radio that uses a hand crank generator and optimized charging circuitry.

What can be done to gain efficiency?

1) Muscle power ==> rotation
The bicycle is one of the most efficient machines ever invented. Hard to improve on this.

2) rotation ==> transmission (lots of friction)
The motor on the tire is turning a lot of energy to friction. A better method would be to use the wheel as a flywheel and connect the drive to the chain. Use a simple set of external lubricated gears to obtain the correct motor rpm.

3) transmission ==> DC generator
Motors will work as generators but actual generators are much better. Since you are using an automotive battery, consider a small alternator for the lowest resistance. Generators with permanent magnents make power at low rpms. Alternators like high rpms. You cannot produce enough power to drive either one anywhere near full output. But you can vary the field on the alternator to match your muscle input.

4) 12v DC to AC inverter ==> 120v transformer to 12DC ==> 12v DC to battery
A lot of wasted energy here. A whole lot. There are ways to bypass the inverter.

We don't actually use AC. All our stuff converts AC back to DC in a wasteful step. This is our energy infrastructure's crazy uncle in the attic. It's because Tesla lost out to Edison and died a pauper. He's dead but we're all still suffering.