I’m going to be at a tradeshow with my older Macbook Pro (magsafe charging connection). No power is supplied, so I’m looking for an external battery to keep the laptop running all day (yeah, the internal battery isn’t going to make it).
Suggestions?
I do have a home UPS unit, but that’s really heavy and I don’t think it has enough juice for an all-day event.
Jackery makes some large power banks that might be enough for you (depending on how much current the laptop draws).
They have some very big (and expensive) models that can probably work for you, but I don’t know if you want to spend that much.
I’ve seen a similar need discussed in the past in professional audio circles - using a laptop to record in locations without mains power. Digging through an archive, I found two links to products, from around 2010. These were products that allow direct connection of a DC source (battery) to a Mac, without using an inverter to convert DC to AC and an AC laptop power supply (since the unusual power can cause artifacts in the recorded audio). The links, and I assume products, are long deceased, so these links are to archived pages from the Internet Archive.
Unfortunately this was pretty niche stuff even back then, so this is more for interest & background than any practical use.
An inverter and AC power supply could perhaps work for you. Or - could you perhaps borrow a more recent Mac for the show, with ability to charge from USB-C? I have no experience with this, but I think that would then allow the use of many currently available cheap rechargeable batteries with USB outputs.
A USB-C laptop might be more efficient here, but note that a cheap battery pack probably won’t have the capacity to keep a laptop running for long. You didn’t say which model Macbook Pro you have, but internal batteries typically have a capacity in the range of 4000-8000 mAh.
But a large power bank device that has USB output may be perfect for such a task.
This would be the easiest way by far to do this, anything else will be painful and expensive, eg one of the large Jackery units. Any modern M1 Mac will work on a stand for what you need, and if it turns out it doesn’t meet your expectations you have a 14 day window to return it.
Turns out I can borrow a friend’s macbook air – although it’s an older version (magsafe, not USB-C). I’m thinking that might use a little less juice than my MBP. Looking on Amazon, I see several reasonably priced powerbanks that offer an AC connection, although I have no idea how long they would last
Would something like this be sufficient?
The Air is still an intel processor so will draw more power than an M1, plus you do not really solve your battery problem. If it was a USB-C Air that would make it a lot less painful, anything that is legacy MagSafe will be painful. It would probably be cheaper & easier to get power to the stand if it is not too late, and yes I know how much that I is likely to cost 
Or test drive a new MacBook 
Buy a brand new M1 MBP. Return it after the show (and within 14 days of purchase) for a full refund. Of course you can’t damage it for the refund to work. But Apple has been really great about this in my experience.
OK… maybe I should try to be more scientific about this. I presume I need to know:
So I need some numbers. When I look for the proper charger for the macbook air, it looks like it requires a 45W charger. I’m assuming that would provide the maximum amount of power the device requires.
But I’m not sure what that means in terms of energy consumption. Does that mean the laptop will consume (at the most) 45 watts/hour? So if I find a power bank (like the one above) at 88 watt hours (Wh) will that give me a little under 2 hours of use?
I have two Ravpower power things that I like.
The big one, about $200 and bought primarily for disaster power, is a ~250Wh with two 250 watt AC outlets (possibly not both at the same time), as well as some usb-3 and a usb-c ports. It’s about 6"x6"x7", and about 5 pounds. It claims true sine wave, though that doesn’t matter for computer stuff (it does matter for things like motors where timing is important). It comes in a nice case so it’s easy to keep all of the bits and pieces together and carry around. Charges pretty fast from the provided charger.
The smaller one, about $50, I think of it as my pocket outlet. It’s about 75Wh with one AC port that can put out 80 watts, not true sine wave, and one each of usb-c and usb-a. It’s about 20 oz, 3"x3"x6" and I use it around the house and out in the yard for black-lighting moths and such. (Old house, few outlets.) It needs to be charged via usb-c (30 watt power delivery), and doesn’t come with a charger, but the big Rav was happy to keep it charged for me until I got around to buying a charger. Not a power efficient way to do things, but it gave big rav some some better exercise than keeping the phone and ipads charged up.
I very much like the two Rav products I have, but I don’t like that they play stupid price games. Every time you go to the site the prices are different, and the firlst visit generally gives you an unknown value coupon (“up to 50% off!”) if you give them an email address. mailinator.com is your friend. Both times I bought something the coupon was 25% off but I don’t know if that’s typical.
