The 180W charger never draws 180W from AC power?

[ByteBender]

I have connected the 180W charger to a wattmeter and it shows readings well below 180W while the FW16 battery is charging. Is this normal?

I have tried connecting the charger to both USB C 240W charging ports (1 and 4) and the result is the same.

Here are my measurements:

When the laptop was quite cold (spent quite some time in my bag while outside) and the battery was a 66%:

• with the system turned off: 20W
• in the bios: 65W
• idle on Linux (NixOS, no special power configuration): 30-35W
• idle on Windows 11 (also no special configuration): 60 W

After letting the laptop warm up, with the battery at 70%:

• turned off: 75W
• bios: 120W
• idle on Linux: 85W
• idle on Windows: 90-110W

I guess it’s normal that it doesn’t charge at full speed when the battery is cold, but shouldn’t it always draw more than 180W from the AC at normal temperature to provide 180W of charge when the battery is charging?

[Christian_Elsner]

The battery charges with 85W max to preserve battery life.

How fast can the battery be charged?

On both Framework Laptop 13 and Framework Laptop 16, the batteries are designed to charge at 1C, and the charging circuitry will only ever charge up to that rate, regardless of the power adapter wattage. That means up to 55W/61W on 13 and 85W on 16. Charging above 1C would require either putting extra wear on the battery that limits cycle life, or using a battery chemistry that has less energy density. There is some loss in the charging circuity, so you’ll need something like a >60W/65W powe…

[Charlie_6]

@ByteBender

I guess it’s normal that it doesn’t charge at full speed when the battery is cold

The framework laptop is not a Tesla, there’s no “battery preconditioning”, room temperature the battery will charge fast. Then again, every manufacturer has it’s own BMS calibration so nobody knows for sure.

@ByteBender

180W of charge when the battery is charging

AFAIK the battery charges at 1.0C(80W) when low charge, 0.7C at above 40% to 60%(hotter is earlier) then finally reduce current (constant voltage) when at 78%~85%

@ByteBender

• with the system turned off: 20W
• in the bios: 65W

Note taken: it’s common for modern laptops that BIOS consume much more power than idling in OS. Thanks for your information

[Adrian_Joachim]

@ByteBender

I guess it’s normal that it doesn’t charge at full speed when the battery is cold, but shouldn’t it always draw more than 180W from the AC at normal temperature to provide 180W of charge when the battery is charging?

The 180W are for charging AND powering the device.

@Charlie_6

AFAIK the battery charges at 1.0C(80W) when low charge, 0.7C at above 40% to 60%(hotter is earlier) then finally reduce current (constant voltage) when at 78%~85%

This, it’ll use at most [battery capacity/1h] for charging (plus conversion losses and all that if you are measuring from the wall).

@Charlie_6

Note taken: it’s common for modern laptops that BIOS consume much more power than idling in OS. Thanks for your information

There is usually no power management going on on bios, just on.