Mavic Air universal battery charger – USB/car
A quick update to my previous article about DIY DJI Mavic Air battery charger. Recently I’ve found quite interesting board on AliExpress, that can be used as universal all-in-one charger.
So first of all, as a reminder, to charge Mavic Air battery we have to supply somewhere around 13,2V. This voltage is usually not available both on USB and in the car lighter socket. With USB we could have, with some new Power Delivery capable one, above 12V – but they are still quite rare and expensive (I’m talking about power banks – not chargers). In car usually we have 12,2-12,4V – when charging it can go higher, but directly on battery – it should not in lighter socket.
So in both cases we have to step-up voltage. It’s quite easy task, and there is plenty of means for this. If we choose right, we can use the same device for USB and car.
But there is another problem, usually USB power banks are able to, at best, give 18W (and this are the new ones). More often it’s 15W or less. The same is with wall chargers. Mavic Air battery tries to charge itself with around 13W. Considering losses for step-up voltage changes – this makes power demand on higher level then most power banks and chargers can give. Safe level is around 10W (2A, 5V). So connecting this battery, with proper step-up DC-DC converter, usually triggers overcharge protection on USB (if there is any) or simply starve device that is shutting down itself.
To prevent this behaviour we need a way to limit current, that battery can draw. And there is additional feature of presented board – we can setup both voltage boos and output current limit.
All we need to do, is set (you even have all displayed on board) output voltage to 13,2V and limit output current to 0,4 (it’s safe value). If we know our USB device can give more juice – we can crank it up on demand.
The only thing that this board is missing, is an ability to trigger fast charge on USB :), but you can still use QC2/3 trigger in between.
Well it seems that there are boards with QC capabilities already 🙂 – look for DP2F/ZK-DP2F board!