Quite strange power consumption in card reader section

[xcity]

I tried your product, which is really impressive, thanks! the screen shows a quite strange power consumption in card reader section, with 4.4w power calculated, I doesn't use this card reader function at this moment. Is it valid to consume that power or it's just mapping to wrong channel?

Thanks!

Dan

[k06a]

Hi Dan,

Thanks for trying macpow, glad you like it!

Regarding the Card Reader showing 4.4W – could you clarify: is this an internal (built-in) SD card reader on your Mac, or an external USB card reader? I don't see an internal card reader as a separate node in the IOReport power tree on my machines, so I want to make sure we're mapping the right channel.

If it's an external USB card reader – does it happen to have an LED or any active indicator? Those can sometimes cause phantom power draw, but 4.4W still sounds too high for that, so it's likely a channel mapping issue.

Either way, could you collect some diagnostic data? Here's what I need:

1. A screenshot of the macpow screen showing the Card Reader power

2. Channel dump – run this and save the output:

   macpow --dump > dump.txt 2>&1

3. JSON snapshot – run this for ~10 seconds, then press Ctrl+C:

   macpow --json > metrics.json 2>&1
   

Please send me all three (screenshot + dump.txt + metrics.json) and I'll figure out if it's a wrong channel mapping.

Thanks!

[xcity]

Anton,

Thanks for reply, I thought I got to know what's happening. I am using M2Max MacBook, it does have an internal card reader (SD card), I thought it was the one, but it is not. The device tree comes under USB section, so it was my CalDigit thunderbolt hub SD card reader. I paste my screen shot for your references. after unplugging my HUB, then it all gone.

Dan

[k06a]

Thanks for reporting this, Dan! Fixed in v0.1.14.

The Card Reader was showing ≈4.48W because we used bMaxPower from the USB descriptor (896mA × 5V) — that's the maximum allocated current, not actual consumption. An idle reader uses far less.

Changes:

• Descriptor-based values now show ≤ (upper bound) instead of ≈ (estimate)
• On MacBooks, real measured power from PowerOutDetails is matched correctly per-device — when available, exact watts are shown without any prefix
• Note: macOS updates real power data with a delay of ~2–5 seconds after plugging in a device (battery kext polls every 1–30s), so you'll see ≤ briefly before the real value appears
• Also fixed: USB devices behind hubs/adapters were sometimes invisible

Update with:

brew update && brew upgrade macpow

Let me know if it looks better now!

[xcity]

I tried newest version 0.1.14, it does show as you described, card reader indicating a ≤ with power, so I understood its max power calculation instead of real power consumption.

[k06a]

@xcity for me it usually starts showing real consumption in 30 seconds. This is an OS limitation we can’t overtake.