I'm struggling to work out how to charge
mavic 2 batteries while in the field, away from AC power.
I have a 2000v Anker powerbank with USB C outputs. Is there any way I can charge up my M2 batteries from this?
USB power banks internally use mostly rechargeable batteries with 3.7 volts. For example, to provide 5 volts at the output, the voltage of the battery is converted accordingly, and this does not happen without conversion losses.
The power loss can be up to 25% and depends on the quality of the installed electronic components.
For example, if the powerbank has 20000mAh at 3.7V, then it's 74Wh, but you'll hardly get more than 55.5Wh from the USB output. Such a power bank will not be able to fully charge a single M2x battery.
In addition, the power banks are often sold with fake capacity specifications. That's why even power banks with more than 20000mAh are too weak to fully charge M2x batteries.
The batteries of the M2x need a voltage of max. 17.4 Volt and for a full charge nearly 60Wh. In addition, the charging process will require slightly more energy than the battery can deliver later, because even here energy losses occur.
Usually Mavic batteries are charged with 1C, which means charging times close to 1 hour. 1C means if the battery has 3. 9Ah, for example, then it will be charged with a current of 3.9A.
In fact, the intelligent DJI batteries accept charging currents from approximately 0.5 amps, as well as above 1C, resulting in correspondingly longer or shorter charging times.
In short: YES, it is quite possible with a USB power bank and a DC StepUp converter to charge a Mavic battery, but it makes little sense. A DIY solution could bring between 10 and 12.5 watts per hour, resulting in a charging time of more than six hours per battery ...