How does fast charge actually work? Why was this never introduced before?
In: Technology
standard chargers works at 5V and up to 2A for most phones. fast charge uses 9V and up to 2A for most phones. the amount of “power” transferred is the V * A. So by using a higher voltage, it charges faster. this requires a more complex circuit, so it’s more expensive. and charging faster always has the potential to wear out your battery faster than charging slower.
The speed of energy transfer is called “power”, and is measured in watts.
Bigger batteries means you want to transfer energy faster (increase watts), so you can charge within reasonable time.
Power is volt times current. (Watts = volt * ampere)
At first, USB was always 5 volt. There’s no simple way to make the voltage variable. The variable for charging speed is current. According to the formula, double current is double charging speed.
A standard USB port cannot supply more than 0.5 ampere. A new USB charging standard came out allowing more than 0.5 ampere, this is generally referring to as *fast charging*. Well, it was. It’s now considered “normal” or “slow”.
The next bottle neck was reached when they got to about 2 ampere (10 watt). The USB plugs is not designed to handle more than that, and there’s no way to get around that without changing the plugs. But in the mean time, what was considered too complicated (=expensive) before, is now doable. The connection is initially 5V, but there’s now several ways that the phone and charger can communicate, and and agree on a higher voltage. It’s usually 9 volts, but its can also be 12 volts or even higher.
Increasing charging speed by increasing voltage is generally referred to as *quick charging”. Which is slightly confusing because some of the standards are actually called Quick Charge (and are owned by Qualcomm), while the rest have different names. Plus it sounds a lot like fast charging.
But it’s all relatively simple, because a USB “charger” is actually not a charger. It’s just a power supply. All the difficult stuff is still in the phone.
Then came the new connector – USB C, and it got even more complicated. Competition with Qualcomm Quick Charge is for example Warp Charge. They actually push up to 6 ampere through the cable while staying below around 5V achieving 30 watts, or Super VOOC that goes up to 10V at 5A, theoretically achieving 50 watts.
It’s really getting really complicated now, because the protocol to negotiate power between phone and power supply is getting increasingly complicated. Both technically and legally. They are also moving at least some of the features needed for charging to the charger. So if you plugin an old fashion “dumb” USB power supply, you get good old fashion charging speed. But if you plugin your original power supply that came with the phone, it replaces some parts of the charging circuitry and enables modern super speed charging.
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