Way to solve the 12 volt charger issue

There's a reason why it won't charge at less than 13V, and it's to not damage the battery. There's a voltage switch in there that has that cutoff in there by design, to give the battery clean voltage.

 

The charger plug has a voltage cutoff switch in it. If you want to bypass it, take it out, but I wouldn't recommend it. It's easier to regulate down than up.

 

Disappointing that something as ubiquitous and cheap as a switching supply wasn't the design -- something that could deliver the necessary 3S LiHV final stage charge voltage (13.05V) at a wide range of input voltages (say, 5-25V). A.k.a. the classic Buck Converter, and many other common designs.

 

You know it could also be that they don't want to drain the car battery accidentally and designed it to only take power when the car is running.

 

I got that information based on the fact someone took their plug apart and there was a simple voltage switch circuit inside. @Robbyg and I being Electrical Engineers analyzed it and came to that conclusion.

 

I would hardly call this "solved"... I bought the car charger to be able to charge batteries on my bike, I don't really see myself carrying another brick twice the size and weight just to be able to use the charger with the engine off..

 

Justin I know we analyzed the circuit several months ago. My memory is not as good as Cyberpowers. I have worked on a lot of circuit designs since then and have forgotten what we found. Maybe somebody who remembers the post can link it.

Many Amateur Radio operators use DC-DC converters for their radios because they also have issues if the voltage drops. The concept works fine if you have dual car batteries but for the 99% of us with a single battery we can easily come back to the car and find the cars battery level at 8V and be stranded at a remote location.

Rob

 

Are you measuring the current at all?

 

You can easily charge three Mavic batteries from your car battery while its stopped with no problems at all.
Three (3) Mavic battery's at 15% flatt = roughly 3000mha or X3 9000 mha or 9amps.
The average car battery, Small is 400amp, large 600amp.
So even after an hour charging 3 Mavic batterys 9 to 10 amps from 400 amp battery isn't going to flatten it. And a five minute idle with a good alternator will replace that back into car battery.
Now the DJI car charger seems to need a full 13.8 volts to provide the battery circuit an even current to charge the cells.
The problem is the car battery is an lead acid and at peak charge per cell of 2.3 is 13.8 but once that float discharge is removed the nominal voltage per cell is 2.1 or 12.6 volts.
And 12.6 is not enough to hold open the input gate on the Mavic car charger.
So you have to use a Buck Converter which takes a lower voltage of between 8 to 12v and supplies a steady output of 13.8 volts. They come in flavors of 5,8,10or15 amp so you would need at least 10 amp minimum for 3 batteries at once.
Or you could go the 12v to 240v inverter route and use your home charger plugged into the inverter.
A little more inefficient but still a cheap fix as you already have home charger and a 12v to 240v 300w can or gigarette plug inverter is only $15 to $20.

 

The car charger isn't just a cheap dumb device, it is capable of handling up to 30V, but the pack could well be the limiting factor on allowing the charge to take place.

If you feed the charger with 12.3-16 V or 25-30 V charging should take place, outside those ranges it won't...

 

Little detail, 400-600 amps refers to how much it can deliver at once to cold crank it. No indication of the capacity. I personally have 665 CCA battery.