Many users report getting close enough for most.

Let's break it down for PastorDave.

The vehicle for charging your battery is of course the charger, so let's start there. The chargers are rated for their output in Ah. The one included with most Juiced bikes is rated for 2 amps of continuous output, until the battery is at a certain level where it switches to a trickle charge. So for our purposes until it's charged, it's a steady 2 amps, and over an hour that means 2Ah of charge.

Next we'll look at how voltage related to Ah (we can measure charge state in Ah or Wh, which is Ah x Volts, but not Vh).

Now the next bit is an estimation based on the cells in your pack, this is from my own calculations. Everyone's, including Juiced Bikes' estimate, is slightly different.

Say my 52v battery is at 48.7 volts and I wanted to get to 56.3V. I want to "add" 7.6 volts. That's 12.27 Ah of charge by my calculation in the original post, divided by the rate of our charger at 2 amps, equals 6.135 hours. Each volt is roughly 1.61 Ah in this range. That's .8 volts an hour.

Now let's say my pack is at 54.2 volts - 13.28Ah. And I want to get it to 56.3 volts - 16.35Ah. I want to add 2.1 volts, which at these states of charge is 3.07 Ah. Each volt is roughly 1.46 Ah in this range. This will take 1.535 hours, or .73 volts an hour

As you can see PastorDave, you may be able to 'estimate' by splitting the difference at .75 volts an hour for a 52v pack, but personally I go by the actual Ah in the pack instead, and divide how much charge I want to have by 2, to give me exactly how many hours I want my bike to be plugged in.