Just as @pauliunas mentioned, we're charging over the USB-C (or TB3) port with USB PowerDelivery (USB PD).
This allows for the V to be compatible with quite a bunch of USB PD compatible chargers like e.g. the Apple one. The maximum charging speed is 9V 3A (27W), if your USB PD charger can deliver more power, the cool thing is that USB PD is intelligent enough that it sees that e.g. the V can only take 27W, and the charger - even 'though it COULD deliver more - will "only" deliver 27W.
I was taking the 5V 3A in my personal statement, as that's the maximum voltage/amperage combination USB PD allows for 5V, before it switches to 9V.