Using USB-C to charge a Mavic Air?

Somewhere I got the crazy idea that it would be fun to bring a camera drone on my bike tours. Every bit of weight counts, of course, so I got a portable one called a Mavic Air.

It’s great, but it uses a custom battery that can only be charged with a large power adapter, and the adapter weighs half a pound. I’m already packing a 5-port USB charger that has one USB-C output suitable for charging a MacBook. That should put out more than enough voltage to charge the Mavic battery. Why can’t I use that?

Well, it turns out I can.

This is a little widget called a PD Buddy Sink. You can plug it into a USBC charger like so:

Then you can program it to ask for any voltage that a USBC power source can supply, and make it available. For example, 15 volts at 2 amps, which is enough to feed into this Mavic Air charger designed to plug into a vehicle’s accessory port:

I removed part of the casing to expose the wires, then linked them up to the PD Buddy Sink, like so:

Then I decided to get arts-and-craftsy. I formed a gross looking extension to the car adapter case, using some two-part epoxy and silicone glue. Now it looks like the adapter is digesting the PD Buddy. Mmm! Delicious!

Using my MacBook, I then programmed the PD Buddy Sink to ask my power adapter for 12.5 to 15 volts at 3 amps, with 15 volts preferred:

And after writing the configuration to the PD Buddy, I plugged it in, and presto! It started charging.

On the left, I’m using the 5-port USB charger to charge my MacBook, with a digital USBC power meter attached. The MacBook has negotiated for 20 volts and is getting about 19 volts. On the right, I’ve plugged the same USB charger into my Frankensteined car adapter, and it’s negotiated for 15 volts. Success!

(If you look closely you can see the adapter is pulling only 0.005 amps. That’s because the Mavic Air battery is fully charged.)

So, was it worth it? Well, I weighed my new Frankensteined adapter, and it’s a little less than 1/4th of a pound. So I’ve saved 1/4th of a pound, but I’ve lost the ability to charge my laptop and my battery at the same time, and lost the two extra USB ports that the power brick provided. Nah, it wasn’t really worth it. But I had a good time!

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