ebike_basics_electrical_terms.md

Ebike batteries have a handful of important ratings that you should check before purchasing any battery. The main two (V and Ah) are commonly listed, but there are some other important measurements that may be more difficult to find:

• Voltage (V): It's useful to think of voltage as pressure in a system. Higher voltage = higher pressure. The voltage of the pack must match your controller and display. Motors are generally pretty flexible in what they can accept. Voltage limits are strict; that is to say, you cannot exceed them. The important caveat there is, of course, motors. A motor's voltage rating isn't actually a max voltage rating, it's a suggestion based on the motor's max amperage and power rating. Why this is the case will become clear later.
• Amps (A): Think of amperage (amps) as the volume of flow in a system. More amps = greater flow. All of the electrical components on your ebike will have amperage ratings expressed as max and continuous. The max number is a "never exceed" number, while the continuous number tells you what amperage the component can support for indefinite time periods. You can peak past the continuous amp rating, but only for short periods, otherwise you'll overheat the component and destroy it.
• Watts (W): Watts are a measure of power, and power is very simply work being done at a given rate. For example, let's say you need to move 500 lbs up 1 foot of elevation. If you do that in 1 hour, that would equate to a given amount of power expended. It doesn't matter if you carry it 5 lbs at a time or 50 lbs at a time, as long as the amount of work being done (weight lifted a given height) and the time remain the same, the power is equivalent. In electrical terms, we use the formula Watts = Volts x Amps. Using some simple algebra, we can use this to derive the third from any pair of these units. So if we know we want 1,000W, and we have a 52V battery, we can simply do 1,000W ÷ 52V ≈ 19.23A.
• Amp-hours (Ah): Amp-hours are a measure of capacity. Be sure not to confuse them with regular amps. This unit tells you how long a battery can sustain a given current flow. In theory, a 13Ah battery can sustain 1A for 13 hours, or 13A for 1 hour. In practice, capacity is reduced as current (amps) increases due to the effects of resistance. For the purposes of comparison between batteries, we'll use a different number, so don't get too hung up on this yet.
• Watt-hours (Wh): Watt hours tells us the energy capacity of a battery, which is a measure of total power, not just amperage capacity like amp-hours. Just like watts, we compute watt-hours by multiplying two numbers. This time it's voltage and amp-hours, so Watt-hours = Volts x Amp-hours. This number is useful for comparing batteries of dissimilar voltage. For example, let's look at two batteries with different voltages, but the same Ah capacity: 52V 13Ah versus 48V 13Ah. For the first, it's 52V x 13Ah = 676Wh, and the second it's 48V x 13Ah = 624Wh. From this, we can see that the 52V battery has greater total energy capacity, despite having the same Ah rating.