I would like to share my attempt to achieve independence from the power plug.
My device is Mod Duo X, It’s stock power supply is 12V/2A , and because of that it is a bit more tricky to feed it outdoors, comparing to the regular guitar pedals.
1) Get power bank with PD. 2) Get USB PD cable with a PD decoy/trigger, that will get 12v from the powerbank. 3) Verify that output is valid by multimeter measurements. .... 4) Profits.
I do not recommend this for playing on stage, or any other case where you seriously need some reliability and your paycheck depends on it. I did not test it enough, and consider this as a way to do some unserious busking, playing with friends outdoors, or a way to eliminate ground loop at home when recording.
For that task I am using power bank, Xiaomi PLM07ZM (20,000mah). This power bank has PD (power delivery) capability, and therefore is able to provide not only 5v voltage, but also 9v and 12v and even 20v for different devices for charging quickly. There are three ports - two of them are USB-A (for some unknown reason I was not able to use it for MDX, but they are rated for 1.5A for 12V anyway, less than required). Third port is USB-C port, and it rated for 12V/3A output, one ampere more than is required. That sounds good enough. Most probably, you can use other power bank with PD capability as well, but pay attention to it’s output possibilities.
Next step is to get these 12v from the power bank. PD standard requires charging device to ask actively for this increased voltage from the charger, and therefore you need a special thing, PD trigger / decoy. This device requests charger to provide some specific voltage. (The same way how tablet or modern phone does)
It is possible to buy pd trigger / decoy as a naked electronic board, provide it with a diy case, and use some soldering skills create your own cable that will force power bank to provide 12v to MDX. Mentioning this in case if you have these in shops around you.
However, luckily, there are some cables that already contain this PD trigger inside. I’ve got a couple from China. Be sure that it has the required voltage, as there are different cables that provide different voltages. I would also seriously advise to use multimeter to verify polarity and voltage, after getting one, to be sure that seller had not mixed things up, and powerbank behaves as expected. Also, repeating this safety procedure for a new powerbank and cable would not hurt.
Anyway, I’ve got a cable like below(It is Jorindo JD0513), but of course it is not the only thing like that on the market:
There is an issue that makes this solution theoretically less reliable - connector barrel is 5.5/2.5mm, while stock MDX connector is mentioned somewhere in the forum threads to be 5.5/2.1mm. Visually, it is hard to tell any difference, to be honest. I could not find any cable with 2.1, unfortunately. Outside diameter is the same, and it fits hole perfectly, but inside - in theory difference makes connection more loose (2.5 and 2.1 is an inner diameter of the plug). I did not notice this to cause any trouble for me (probably because it is spring-loaded, and that allows to maintain contact regardless), but it would be more comfortable to know that connector is actually the same.
Anyway, I found this cable to provide required voltage with required polarity, declared amperage of my power bank has even additional 1A of headroom compared to stock, so it seems suitable.
At about two hours of running MDX with about 47% of CPU load, my three years old 20k mah power bank switched to show 50% capacity with it’s 2 of 4 leds. Therefore, I think I am guaranteed to have at least 3 hours of autonomous playing, and most probably can hope for four.
UPD: Power bank finally gave up after 6 hours and 10 minutes.
Hope my experience could be helpful for somebody.