Anker PowerDrive 2 Alloy Car Charger on a MacBook Air: Measured
Anker's 24W dual-USB car charger measured on a MacBook Air: 7.1 W delivered. USB-A means no Power Delivery, and BC 1.2 caps it at 7.5 W no matter what the label claims.
Anker’s PowerDrive 2 Alloy, the little aluminium plug that lives in a car’s 12 V socket, tested against a MacBook Air with a low battery, per the methodology.
The numbers
| Rated | 24 W total (5 V at 4.8 A, 2.4 A max per port) |
| Negotiated | ~8 W (5 V up to 1.5 A) |
| Live draw | 7.1 W (4.9 V at 1.43 A) |
| Protocol | USB BC 1.2 |
Profile menu: one entry - ~8 W (5 V up to 1.5 A). There is no ladder to climb.
Two ceilings, not one
The label says 24 W, and the Mac took 7.1. Two separate limits are stacked here, and neither is a fault.
No Power Delivery. These are USB-A ports, and USB-A has no PD handshake. Without one there is no negotiation and no high voltage - just a flat 5 V. Every laptop-grade charger in this series climbs to 15 or 20 V, because higher voltage is how you move real power through a thin cable. This one never leaves the bottom rung.
BC 1.2. With nothing to negotiate, the Mac falls back to the oldest standard the two share: USB Battery Charging 1.2, whose dedicated-charger mode allows 5 V at 1.5 A. That is a 7.5 W ceiling, and the measured 7.1 W is that ceiling in practice. The charger’s 2.4 A per-port rating never gets a chance - the Mac will not ask for it.
So the 24 W on the box is the sum of what two phones could pull. It was never a number a laptop could reach.
What it is actually for
Phones and tablets, which is exactly what it was built for. On a MacBook it will hold the battery roughly steady, or gain slowly with the lid closed, but it is a trickle rather than a charge. If you want real charging in a car, you need a USB-C car charger that supports Power Delivery.
Buying one
The Anker PowerDrive 2 Alloy is a solid, compact two-port car charger for phones and tablets. Just do not expect it to charge a laptop.
The Amazon link above is an affiliate link. As an Amazon Associate I earn from qualifying purchases.