Mavic 2 Car Charger - low voltage cutoff circuit / teardown

[benl]

The following's an FYI for anyone interested in what's inside the Mavic 2 Car Charger's car plug (this one: Mavic 2 Car Charger - DJI Store). (how's that for an esoteric topic?)

As I do for all my 12V devices I have replaced the standard car ("cigarette lighter") 12V plug with an Anderson Powerpole connector. Normally this is a simple matter of removing the car plug and installing the Anderson.

The Mavic 2 Car Charger plug is not so simple: it actually contains a PCB with a couple of ICs and a surface mount 15A fuse. The ICs are a dual-opamp with voltage reference (AP4310) and MOSFET (T4002LS), from what I can tell this circuit implements a low voltage cutout (and probably reverse polarity and possibly over-current protection as well, but I didn't test that). It's a low-side switch, the +ve line is continuous and the -ve is switched by the MOSFET.

The circuit cuts off at 11.3 V, and turns back on at >12 V (-ish, I didn't pay a lot of attention to the hysteresis). This is a good cutoff voltage to not flatten your car's battery. It pulls a constant 2.5 A from my benchtop power supply at any voltage from 12-14 V (with a ~1/3 charged battery, if that makes a difference).

Mechanically, the car plug centre pin is on a spring formed from a strip of metal, there's an odd wiper mechanism the purpose of which escapes me (maybe just to keep the plug aligned if it gets pushed too far in?).

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[THE CYBORG]

So do you still use the DJI plug ?

 

[Camino Ken]

As a retired electronics engineer I find this interesting and I agree with your assumptions. I am a little baffled as to what problem you are trying solve by replacing the connector. Is it more robust? I have never (that I recall) had a cigarette connector fail.

 

[sonof40]

Excellent topic/idea and well written. Thanks.

 

[benl]

Re. "why replace the cigarette plug": I'm in a van kitted out with Anderson Powerpole connectors for my "house" 12V system. In my experience Anderson Powerpoles are better than cigarette plugs by every possible measure, for example lower contact resistance and higher current rating (can be up to 45A, though tbh that's really pushing it). I'm not a ham, but these are some of the reasons why ham radio people use these connectors I do have a short cigarette lighter plug to Powerpole adapter if I ever need to use my stuff on someone else's car.

For the Mavic charger at 2.5A, the cigarette plug is fine and if it weren't for my particular setup, I wouldn't have changed it.

I posted mostly to provide some info on the low-voltage cutout circuit, as I've seen some discussion here on that topic; you may be able to remove the cutout just by removing the board within the plug.

 

[Oto]

Why it blows my portable battery bank with cigarette lighter socket 30A fuse when connecting ? This battery was meant for portable boat light with dual-socket 100w halogen lamps so should have enough power.