Charging and 12V power, for phones not cars

What this section covers

The 12V socket in your dashboard is the oldest interface in the car and it is still the most useful one. It is also the accessory category where the marketing is least connected to the specification, because almost every charger is sold on one number — total wattage — and total wattage is very rarely the number that decides how fast your phone charges.

The number on the box is the wrong number

A charger advertised at 67 W might deliver all 67 from one port, or it might cap each port at 35 W and only reach 67 when three devices are plugged in. Those are very different products at very similar prices, and the difference only appears if the maker publishes a per-port table.

Anker's 335 and 535 are the clean illustration: identical port counts, identical 67W headline, and the 535 will put the whole 67W down one USB-C port at 20V and 3.35A while the 335 stops at 35W per port. For phones that gap is invisible, because nothing with a phone battery in it draws more than 35W. For a laptop it is the entire decision. The head-to-head lays out both published tables side by side.

How much do you actually need?

Roughly, and these are the figures the arithmetic on the wattage page works from:

• A phone on navigation with the screen bright can consume power almost as fast as a weak charger supplies it. This is why a phone sometimes drops charge while plugged in — it is not a fault, it is a budget problem.
• Most phones cap between 20 W and 45 W regardless of what you plug them into. Above the cap, extra watts do nothing at all.
• A Qi2 wireless mount typically needs a 20 W or better USB-C source to hit its rated 15W output, which is a hidden cost of buying a wireless mount.
• A laptop wants 45 W to 100 W, and that is the only case where the per-port ceiling justifies the more expensive charger.

PD and PPS, briefly

USB Power Delivery is the negotiation protocol: the phone and the charger agree a voltage and a current rather than the charger just pushing 5V at whatever it likes. PPS is an extension that lets them adjust in fine steps rather than jumping between fixed voltages, and it is what several Samsung phones need to reach their advertised fastest charging. A charger without PPS will still charge those phones, just not at the headline speed. Both chargers ranked here support both.

The socket itself has a limit

Your car's 12V socket is protected by a fuse, typically 10, 15 or 20 amps depending on the vehicle, and that fuse is the real ceiling on everything plugged into it. At 12 volts, a 15-amp circuit supplies about 180 W before the fuse is the constraint — which is far more than any phone charger asks for, and less than some tire inflators want. It is worth knowing before you plug a compressor into the same socket as everything else. The inflator page covers which tools need to go to the battery instead.

What we do not do here

No power-meter measurements, because we have not made any. What we publish is the maker's own PDO table where they release one, the input rating, the protocol support and the warranty, with the source attached. Anker publishes a complete voltage-and-current table for the 535, which is unusual and is one of the reasons it is here. The method is here.