Power consumption

uConsole
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I’ve just made some current measurements on my uConsole, CM4. It looks like this:

Screenshot 2025-04-25 at 18.36.59
Screenshot 2025-04-25 at 18.36.591752×1084 66.6 KB

Conditions: wifi up, CPU around 300 MHz (“ondemand” profile), no additional USB, charge ~90%, 4V.
Data source:
/sys/class/power_supply/axp20x-battery/current_now
/sys/class/power_supply/axp20x-battery/voltage_now

I also compared the current_now and voltage_now values with a physical multimeter in the power-supply circuitry. Unfortunately, I could only test with a single 18650 cell, so my data were limited. I just wanted to see how close current_now was to the actual value. It was fairly close: current_now ~600 mA, multimeter ~570 mA (5% difference).

I used a custom “sleep mode” script based on SLEEP support development for CM4.
In “sleep mode” power consumption drops to 1.5 W.

The maximum consumption I’ve seen so far (1500 MHz × 4 CPU cores at 100 %) was around 6 W.

So yes, a device like this could benefit from an e-ink display… but without a proper sleep mode, the CPU would still drain power quickly even if throttled. I don’t think it could run on less than 300 mA.

The best mod (for my use cases) would be a bigger, faster-charging battery.

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The uConsole has enough space in the back to fit an extra 18500 (as opposed to 18650) Li-ion battery. The maximum capacity of these seem to be ~2000mAh, which is what I got. You can get those that have pre-soldered wires and you’ll only have to attach the other end.

Yes, it’s not ideal to use 3 batteries with different capacities. But all 3 are in parallel – the axp228 PMIC doesn’t really care about the number of batteries anyway. Even with just 2, you fully rely on natural balancing that happens due to the fact that they are connected in parallel.

With a different battery configuration you’ll also need to reconfigure your device tree and re-calibrate the PMIC to get accurate reporting, something like what I did with the Arch kernel: Arch Linux ARM for uConsole w/ RPi CM5 - #42 by PeterCxy

(None of the battery mods solve the charging speed issue. Charging current is limited by the PMIC and I don’t think you can fix that without getting a different PMIC.)