When you use a DC charging station – CHAdeMO and Supercharger are the varieties in active use, with CCS coming soon – the power is converted by the station, so DC goes straight in to your battery (not really, but close enough for this discussion). When you plug in to AC power – whether you plug in to a 120V or 240V outlet, or use J1772 charging equipment – your car converts the power to DC. Both sides have DC, so no conversion is required. It is simply a USB cable, which allows my tablet to charge from a DC USB port in a car or laptop. Here is the DC charging solution for my tablet computer.

The key to understanding AC versus DC charging is learning where the box is, and why. You’ll notice that the more power the device uses, the larger that box is.

Portable electronics that recharge from wall power all have one: it is usually in a black box in the charging cord, along with some other components we will ignore. This conversion is done by a “rectifier”. Stationary appliances that use electricity directly from an outlet – lamps, refrigerators, washing machines – use AC power.īecause the electric grid provides AC, the electricity must get converted to DC when you want to charge a portable device. That is why AC power comes in through the power lines to your home, and is what is available at power outlets. Plug-in vehicles are portable so they use DC batteries too (although most of them have AC motors – a complicating step we may consider another day).ĪC electricity is a little more complicated because it switches back and forth, but a key advantage is that it can be transmitted economically over long distances. That is why portable electronics – flashlights, cell phones, laptops – use DC power they have to store it. A key advantage is that it is easy to store in batteries. The reason we have two types of charging is that there are two “types” of electricity, AC and DC so we shall start by discussing them.ĭC is the simple positive-and-negative type of electricity that you probably experimented with in 7th grade science. Technical details are intentionally glossed over here.

But for the curious, this is a simplified explanation of the difference between AC and DC charging. DC is faster, and that is all that they need to know.

Charging with ac over usb 2 vs usb 3