WH, AH , V
I would like to understand how to read those numbers and see how many times a power bank charger can recharge my phone or laptop.
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WH – Watt-hours
AH – Amp-hours
V – Volts
A common intro analogy to electrical flow in wires is to liken it to a fluid in a pipe. It’s not a perfect analogy, and it starts to break down when you get into the specifics, but for a really basic understanding, it’s pretty intuitive and useful.
Voltage is analogous to pressure. If you have a high pressure on one side of a pipe, and a low pressure on the other, fluid will flow. Similarly, if you have a high voltage on one side of a wire, and a low voltage on the other side of the wire, electricity will flow. The higher the voltage difference, the faster the flow, same with pressure.
If you put too much pressure on a pipe, it can burst. Similarly, if you put too much voltage difference a wire, it can melt or burn up. So a device’s V rating is essentially telling you what its “pressure rating” for electricity is. Don’t exceed it, or you can fry out the device.
Amperage is analogous to flow rate. In a pipe, you can measure how much water has moved through the pipe in a given unit of time. Amperage tells you how much electric charge has flowed through a wire in a given amount of time.
If you multiply flow rate by time, you just get an amount of fluid. If I had a pipe that has a flow rate of 1 liter per minute, and I let it flow for 5 minutes, I’d have 1 * 5 = 5 liters of water. So, multiplying amperes, a sort of “flow rate” for electric charge, you’ll end up with an amount of electric charge. That’s what an Amp-hour is. It’s a slightly convoluted way to tell you how much charge potential a battery can store. If a battery holds 100 Amp-hours, that means the battery can (in theory) deliver a consistent flow rate of 1 amp for 100 hours. Or 100 amps for a single hour. Or some other combination. The voltage you apply will determine how fast it will flow, and since you have how much charge the battery has in total, you can calculate how long it will last for a given flow rate. Just like how if you had a tank with a known amount of capacity, and a drain in the tank with a known flow rate, you can calculate how long it will take for the tank to be empty.
Watts are a unit of power. It describes using a certain amount of energy over a certain duration of time (specifically, 1 Joule per second). In a way, it’s a “flow rate” for energy. So, just like with the amp-hour, a watt-hour is a slightly roundabout way to describe an amount of energy. This tells you directly how much energy storage capacity the battery has.
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