Any harm in using a lower powered (45w or 60w) power supply for my MBP 16"? Anyone know what the peak power draw is?

Thanks but I'm looking for something a bit more technical than "If you use a power adapter that is lower in wattage than the adapter that came with your Mac, it won't provide enough power to your computer" :)

Because I don't care if the battery won't charge when using the laptop, or will only charge slowly when not using the laptop. I'm wondering about getting a 45W or 60W PD battery bank for use on the go - my thinking is that if I use it when the internal battery is fully, or nearly fully, charged it should still give me a lot of extra usage time even if the internal battery is used as well as the battery bank.

It might even reduce ageing on the internal battery, compared with just running off the internal one, by reducing current load on the internal battery.

Obviously, if the laptop's processor and GPU etc are using more than 45W or 60W when the internal battery is drained that'd cause a problem which is the reason for my question about system power consumption not including charging the internal battery.

Follow-up - the edit timer has expired but I wanted to re-word my paragraph about 1-hour battery life doing demanding tasks not being likely, because it's clearly perfectly possible. Rather, if that were the case I'd expect to see more complaints about battery life.

Then can you explain why the Wh rating of the battery is relevant to my question please? What am I missing?

And indeed, I do credit Apple engineering magic, which brings me back to the reason for asking my question in the first place.

I get all that in your first sentence, that's basically the idea of Watt-hours. I don't really understand how that links to the thermal characteristics of the Macbook though - my understanding is that the battery's capacity is limited by airline carry-on limits of 100Wh, and I think the PSU is limited either by USB-C specifications and/or by the physics of keeping the PSU block small enough to be portable.

I've come across plenty of battery life complaints of people saying it only lasted 4 hours or so but can't find any reports that battery life when rendering or gaming is just a couple of hours, but maybe that's the case.

Sorry, just to clarify again (can't edit now) - of course I get how the PSU output would be linked to the system TDP, but I think it's more likely that the system TDP was designed around the 100W restriction of the USB-C PD specification rather than the other way round.

The Wh of the battery doesn't tell us anything about the question I'm asking. I can only presume you don't fully understand what Watt-hours are?

A more definitive answer to what Apple describes in the support document absolutely is possible if you understand electronics, electrical principles and computer components. And there must be more going on under the hood with power management than is first apparent, because on the face of it 96W isn't enough to run the CPU and GPU at full tilt along with the rest of the system.

To explain, the TDP of the i9 in the MBP is 45W, which considering that's with all cores running at base frequency that seems to leave plenty of headroom - but the TDP of the 5500M is another 50W, theoretically leaving no headroom for the rest of the system, not least the screen.

Furthermore, all this would also mean that the 99.8 Wh internal battery would only last about an hour when doing demanding tasks which I don't find very likely.

Anyway, never mind - I think this is best answered by experiment, and if it's not something anyone's played with I'll be able to run my own experiments using coconutBattery once my laptop arrives.