Just a follow-up to say that I installed the replacement battery and all is well now. Also, the CPU performance is now as expected.

One thing that I noticed is that the maximum charging speed is 40W and the maximum the system can pull is around 50W. I thought that was interesting given that the information I read elsewhere said there was a 30W limit on this model.

This model is just passive cooling with no fans.

I have the original OEM adapter (I believe) which is 30W. I also have a second Apple 60W adapter, which belongs to my MacBook Pro. Lastly, I have a Dell 65W adapter.
From my understand, the max for this model is 30W, no matter what you use.

I don't have the USB-C power meter, but will look into that as it'd be a useful tool to keep around.
I do have a Kill-a-Watt which measures line voltage/amps/watts, which gives some idea anyway. I never see much beyond 7-8 watts, even at full load on Cinebench.
...

One further question. Is a defective battery known to limit CPU performance?

I noticed when running Cinebench, the score is much lower than typical 2855 multi-core / 1136 single-core.

Running powermetrics during the multi-core test, I can see the E-cluster at the maximum frequency (2064 MHz), however P-cluster is at a low frequency (828 MHz). Both have 0% idle residency.

I don't think it's a thermal throttle as the core temperatures is only ~40C.
CPU power is only showing ~1900 mW.

Thank you for the reply. I checked and True Tone is enabled and working. I noticed coconutBattery shows the manufacturing date of the battery and laptop is in 2022, so if it sat on a shelf since then, it is logical the battery is the problem.

Hello. Sorry for the long post, but I am trying to decide if this is a simple battery replacement, or potentially something more complicated.

I bought an open box MacBook Air M1 2020 A2337. Seller claimed it was never used. Visually, it appears pristine.

On arrival, the battery was completely flat. Computer powers up and boots fine. Battery status showing 1% and charging, 1 cycle. coconutBattery showing 0 mAh and ~6 watts.
After some hours, the battery status did not improve. Restore via DFU did not help.

I connected the power adapter to a Kill-a-Watt...

Hello! Just another user from Canada hoping to learn more.