VoilamartQA How to choose a hub motor wheel ebike conversion kit for your bike - The voltage selecting

Just imagine, you have a balloon and also a metal high pressure air tank, they have the same volume, which one will contain more air?

According to US aviation related regulations, travelers are only allowed to carry batteries of up to 300 watt-hours on board. However, the batteries we usually see are labeled in the format of "Volt-Ampere-Hours", so can my battery be carried on board? This article may help you.

First of all, watt-hours = voltage X amp-hours.
So, if you have a 48V 15AH battery, I'm sorry, but 48V X 15AH = 720WH, and that battery will not be allowed on board.
Then if the battery is 48V, 300 watt-hours means only 300WH / 48V = 6.25AH.
But if the battery is 36V, 300 watt hours means 300WH / 36V = 8.33AH.

However, for some reasons,
the 36V hub motors can only be produced up to 1KW,
while 48V motors can up to 2KW.
As said in the opening example:
Voltage can be thought of as the pressure of electricity,
and current as the speed at which it flows.

If you think of a battery as "a storage bottle for electricity", isn't it easier to understand the battery's "Amp-Hour" (also shows as "Ah") as "how many amperes electricity could output from the battery in 1 hour"? I think the answer is: yes.

It's true that a 36V battery takes longer to do the same thing than a 48V battery because it's less "stressed inside". But if you compress the time to the same length, then the "amp hours" of a 36V battery will be higher than that of a 48V battery.
That's why a 36V battery will have more amp hours than a 48V for the same 300 watt hours.
So, if you need to carry batteries on board, I would recommend the 36V system.

But as said above, a motor adapted for 48V puts out more power. If you have a requirement for the bike to carry heavy loads, or need to go uphill, the 36V system may not be able to accommodate that.

Overall:
If you only need a daily ride, perhaps the 36V system will suffice. It can ride farther on the same amount of power.
But if you need to ride with a heavy load, or if you need to go uphill, a 48V and higher voltage system might be better for you.