A battery has a voltage and can supply a certain current for a period of time. You could have a 12 V battery that can deliver 100 A of cranking current or one good for supplying 100 A for an hour.
This will depend on the size of the 12 v battery.
There is a wide variety of pricing for a 12 volt battery. The overall wattage of the battery will determine overall cost. Typically they will cost anywhere from $100-$400 for a new battery.
Standard 6 volt motorcycle battery aabout $50 to $100
About 2 hours if the battery is 100% discharged.
6.32 volts is 100 percent charged
12 volts is enough for a 12-volt 100-watt light bulb. It would not be enough for a 120-volt or 240-volt bulb.
They don't. Car batteries produce 100's of amps of current. a 1.5Volt flash light battery produces milli-amps at best.
You "could" run a 120V 5A window AC unit off a 12V deep cell battery but, assuming 100% efficiency (something you can never get), you would need an inverter or motor-generator set and 50A out of the battery to run, and maybe 5 or 10 times that to start.
Check the voltage at the battery with a DC volt meter. It is reads 12.6 volts is it 100% charged. 12.4 volts 75%, 12.2 volts 50%, and 12.0 volts 25% charged. Less than 12.0 volts is a dead battery. If the battery will not hold a charge with the negative cable disconnected it has a dead cell and must be replaced.
The difference is 100.
the difference is 900, since 1000 - 100 = 900.
The 12 volt fan will draw 100 mA from a 12 volt battery. You don't need to do anything to reduce the current. Your battery rating is probably really 1100 mAh; 1100 milliAmp-hours. You should get 11 hours of operation from your 1100 mAh battery if your fan is only drawing 100 mA.