They’re usually called “keep-alive loads” or “dummy loads” (less commonly “load resistors”).
In practice you’ll see them sold under a few more consumer-friendly names:
- USB keep-awake dongle
- Power bank keep-on adapter
- Constant load resistor (USB load)
- Trickle load / minimum load adapter
- Anti-auto-off adapter
What they do
Most power banks switch off when the current draw is too low. These little plugs deliberately draw a small steady current so the bank thinks something is still connected.
Typical form
Usually a small USB-A plug with an internal resistor (sometimes a resistor + capacitor network), e.g. drawing ~50–200 mA continuously.
Related feature (not hardware)
Some newer banks instead have:
- “Low-current mode” / “always-on mode” (a button setting rather than an attachment)
15 June 2026: I purchased from Lidl, UK, an Ultimate speed power bank with compressor UPK 10 H5. This power bank provides 12V and 5V output with USB-A and USB-C outputs. Trials have shown that it remains on for several hours with the UKRAA PicoMuon detector, solving the powering issue for me.