High cell voltages accelerating Macbook battery degradation?

[furmonster]

I've been looking at battery voltages of the M1 and M2 Macbook Air, although I would suspect that any recent Macbook will have the same behaviour.

ioreg -w0 -f -r -c AppleSmartBattery

gives a whole load of debugging information about the battery, including the current voltage across the battery, and the voltage across each of the three cells within it.

I was a bit surprised to see that when charging to 100%, the battery is held at over 4.3V/cell while charging, which on completion drops to 4.25/cell.

I'm not a real battery expert, but I know from my time on batteryuniversity and my experience with EVs, that cell voltages over 4.2V cause rapidly accelerated degradation of lithium ion batteries, especially when the battery is warm. In the common use case of "Macbook used mostly on mains power and battery sitting at 100% while system gets warm from use", this seems an unfortunate setup.

Does anyone know anything about the specific variant of lithium-ion chemistry used in Macbooks, how it is optimised, and how these high voltages impact it?

[I know that this can be managed with AlDente, and that AlDente has its own problems with the BMS seemingly becoming confused about the battery's state of health and remaining capacity. Please don't comment about that here, I'm interested only in learning more about the battery and its management.]

 

[Mike Boreham]

Thanks for interesting angle on battery health. I am not an expert either and doubt whether you will get the level of expert replies here. You have probably seen this article since you mention Battery University site. I just had a look at my recent cell voltage history and confirm what you say.

 

[furmonster]

Thank you for the reply. I'd be grateful for pointers to a more appropriate forum. This one seems to have a lot of Mac knowledge; Reddit is pretty juvenile, and I don't know how to gain traction on twitter with a question like this.

 

[Mike Boreham]

Thank you for the reply. I'd be grateful for pointers to a more appropriate forum. This one seems to have a lot of Mac knowledge; Reddit is pretty juvenile, and I don't know how to gain traction on twitter with a question like this.

I don't know either, not for lack of looking. I doubt anyone outside Apple knows anything about the specific variant of lithium-ion chemistry used in Macbooks, how it is optimised, and how these high voltages impact it.

Maybe someone will chip in.