As the MacBook Air's power supply was being used to charge the iPad Air, I used an external battery to power up the Mac while performing the bi-weekly clone and Time Machine backups. The normal power supply provides 30W vs 45W for the battery. Once the backups were done, the battery pack was 50% depleted, I needed some way to charge it. All the USB-C ports on the Mac Mini and Apple Studio Display were in use for other duties so I fished out a Thunderbolt 4 dock I rarely use these days. It has three downstream ports and gets its power from a 230 volt power brick rated at 6A. All three Thunderbolt 4 ports are capable of powering external devices at 15W each. It makes no difference whether one or all three are used, each one puts out up to 15W, so that's how I'm charging thr battery pack.