I have a generic 1000 watt hub motor that is new and it has never been used. I ordered batteries, but I didn't have cables to hook everything up properly. I tried one battery without charging it and I didn't get so much as a flicker of light. Do I have to have all batteries charged before any indicator light would come on? I am hoping this bike hub motor is going to work and I am charging the batteries one at a time. Can one battery be used to see if things will function on this bike or do I have to wait until I charge the complete set of my batteries making it 48 Volts?
Your 48 volt motor probably uses some modern flavour of lithium battery. It will probably refuse to run on anything less than 44-46 volts (actual numbers may differ) and this will be in the controller's manual.
If you're using 12 volt SLA lead acid batteries, then they must not be discharged below 10.5 volts per battery, which would be 42 volts in your scenario.
To get 48 volts, you will need 4x 12V batteries in series not parallel. 12V batteries in parallel will still only give 12 volts, just a lot more current for a lot longer. Since your motor is 48 volts it won't even start on one 12V battery.
I recommend you use the fattest wires you can to link your batteries. Electric cars eschew wires in favour of busbars for added cross sectional area.
If this sounds like alien gibberish, you should enlist the aid of an electrically-minded assistant.
As an aside, you'll need to change a lot of how you ride once you have that much power on tap. Riding in the door zone becomes a game of Russian Roulette, and you'll have to ride much more defensively, which means scanning ahead, eyeballing possible threats, and anticipating what might happen.
Also some locations would call a 1000 watt motor an electric motorbike, not an assisted pedal bicycle. You may need to check this out.
It would help a lot to know what motor you have and the batteries that you are using – it would make it much easier to offer specific help.
The answer to your question depends on how the batteries will be wired. If they are, say 12 volt, batteries that are wired in series you will need to have them all charged before it will power up. If the batteries are 48 volt batteries that are wired in parallel, then one should do it.
I suspect that the batteries are set up to be wired in series, but without more specific information it is impossible to do more than guess.
When you wire batteries in series, the voltages add up. So until you've got at least the minimum running voltage in the batteries it won't start up. When the batteries are wired in parallel they all, in theory, contribute equally to providing the current that drives the motor. In fact there are slight differences between the batteries that prevent this and one of the batteries will take most of the load. As with people, this doesn't usually work out well…