How much is the cost of the electric use for my ebike?

12 Ah at 48 volts delivers 576 watt hours or 0.576 kwh.

so the cost of electricity is about 6.9 cents per charge if you run it down

plus the cost of replacing the battery after a year or so - my deep discharge battery for my mobility scooter costs $150, of course having a lot more amp hours.

Since the electrolyte in a battery isn't the greatest conductor (compared to copper) and there is overvoltage required to charge a battery, you will need to put in about 40% more power into the battery to get that 12ah back from the battery.

Plus, you never get to use the whole 12ah because batteries lose performance quickly after they are about 75% discharged. So maybe you will get 8 ah out of the battery before you need to recharge

Then like I said, you will need about 40% more charge to get that 8 ah back into the battery so,

8ah * .4 = 3.2ah

8 + 3.2 = approximately 11.2 ah to charge back up from a battery with 4 ah remaining

11.2 ah * 48v * .12 = about 6.4 cents per charge

Use a simple math that I learned in grade 4 from China.....

1000 : 550 = 12 : X

X = 550 * 12 / 1000 = 6.6 cents