Short answer: pass-through charging means a power bank, hub, dock or monitor passes power on to your device while it is itself connected to a charger. It is handy on a desk or nightstand with one socket, but it has real limits. The output is usually capped by what comes in, ports can switch off for a moment when you plug or unplug the charger, the unit runs warmer, and many power banks do not support it at all.
Our power bank guide introduced the feature. This guide explains the limits, the safety side and what to check before you rely on it.
Where you will meet pass-through
- Power banks that charge your phone while they are plugged into the wall.
- USB-C hubs and docks with a "PD in" port that feeds power on to your laptop.
- Monitors that charge a laptop over USB-C while displaying.
The laptop side, including how much power a hub keeps for itself, is covered in our laptop USB-C charging guide. This guide focuses on power banks and on the dropouts that affect all three.
Limit 1: the output is capped by the input
A power bank in pass-through mode can only hand on what its own charger gives it, minus losses. Anker is unusually precise about this for its 25,000 mAh, 165 W power bank. Pass-through only starts when the input is 20 W or more. Below that, the bank just recharges itself. If the output asks for more than the input, the bank limits the output to less than the input. Anker's table shows how this plays out. It applies only to that model (A1695); other power banks, including other Anker models, behave differently.
| Charger feeding the power bank | One device on USB-C | Two or three devices |
|---|---|---|
| Below 20 W | No pass-through |