I want to build a bike generator to charge a bank of batteries.?

Question

Then connect the batteries to an electricity outlet to power lights and appliances

Answer 1

Mount bike in stand or use an exercise bike.

Charging:
Bike drives an automotive alternator by using either a belt or friction drive. Alternator connected to battery and voltage regulator, you will also need a switch to dissconnect the alternator and or battery when not in use to avoid discharging the battery.

Voltage Conversion:
This may be the easiest part as all you will need todo is connect an inverter to the battery. The inverter will convert 12Vdc to 120VAC 60Hz. The ammount of useful 120VAC power you get will depend on the size of the inverter and electrical load you place on it. Running a ligh load like a laptop charger you could get several hours of use while a heavier load like a TV may only last 1/2 hour or less. It all depends on what you plug in the size of the battery and how much you pedal to charge it.

Answer 2

You will be unpleasantly surprised at how little power you can generate by pedaling. The average person can only drive a car alternator up to about 4-5 volts and keep it up for 5-10 minutes, depending on physical conditioning.

Commercial exercise bikes use a small generator made from a 12v motor like the motor in your car's dashboard fan. Just a 1-watt, 400 ohm resistor can put more of a load on it than most people can handle.

So it's not as obvious an idea as it seems. Maybe you can come up with something that works.

Good luck.