Electronics gurus - hacking the car charger?

[idiogenic]

Hi guys, 1st post woohoo! I hail from sunny QLD, Australia.

Anyway, the car charger is a piece of ****. I have a dual battery system in my 4wd from which I am unable to charge the Mavic batteries with the DJI car charger because of it's 13V input voltage requirement, which is only achievable with the engine running or my solar panels in full sun.

I suspect DJI have cut some serious corners here by only including the ability to down regulate voltage to match the flight battery, and have not included any up regulating ability. It does beg the question - what does the black box really do, given that the charging intelligence appears to be in the battery, not the charger, and that the input voltage is pretty **** close to what is required anyway?

I saw another post on here where someone mentioned a Drok voltage up-regulator (Amazon link: Amazon.com: DROK 600W 12A DC Boost Voltage Converter 12-60V to 12-80V Step-up Power Supply Transformer Module Regulator Controller Constant Volt/Amp Car: Industrial & Scientific) so I've bought one of these.

I have one in hand and going to wire it in soon but I have a question: what is the chip inside the 12v plug of the DJI charger? DJI specs say it has a thermal cutoff if the cigarette socket exceeds a certain temperature, which seems like a strange variable to monitor - why not just install a regular fuse or current based circuit breaker?

Does anyone have an electronics background and can you comment on what is going on with this chip?

If it can be replaced with a regular fuse that would be much more convenient - having 3 separate boxes/dongles in the charging system will just be annoying, and I need a fuse upstream of the voltage regulator anyway (although it has one built in).



And here's the other side of the chip:



Also, specs on the charger indicate input voltage of '13V/26V' - the '/' seems to indicate 'or' to me, not a range of 13v-26v. Does this seem right? Or would any input voltage in the range 13-26v be sufficient? Reason being, I'm not yet sure how stable the output voltage of the Drok regulator is going to be under load and with declining input voltage.

 

[Cyberpower678]

I'm an electrical engineer, but I can't really do anything to help with just a picture of a chip. It would be nice to look at some schematics here so I can tell you exactly what it does and how to "hack" it.

 

[idiogenic]

Unfortunately I doubt DJI is going to give me a copy of the schematics!

 

[Cyberpower678]

Unfortunately I doubt DJI is going to give me a copy of the schematics!

Then how about a high-res shot of both sides of the chip. Maybe I can build my own schematics if I can trace the pathways.

 

[Robbyg]

What are the numbers printed on the 8 pin IC ?
Hmm just noticed that you are showing both sides. So there are two IC's on the board and I also see a 15Amp fuse.

 

[Cyberpower678]

What are the numbers printed on the 8 pin IC ?

If I had to guess it would be an op-amp. It makes to use one as a switch given a certain input voltage.

 

[Cyberpower678]

I'm also curious to know about the 6 pin IC as well.

 

[SteveT]

You have dual batteries so you could rig up a 24v charging outlet.

 

[idiogenic]

Thanks guys, here's some close ups.

I'm going to call this 'Side A':



It's a bit tricky to get a clear shot of Side B - the wires overlying the board don't really want to move.


Googling the IC on Side A gets me to this document:
https://www.diodes.com/assets/Datasheets/AP4310E.pdf

I know SFA about electronics, but this is making me think that the element inside the cigarette plug isn't just a simple thermal cutoff?

 

[idiogenic]

You have dual batteries so you could rig up a 24v charging outlet.

Good idea, hadn't thought of that!

It's a bit difficult though, the second battery is not located anywhere near the engine battery and I'd have to bypass the battery isolator and ensure I didn't do something that was going to put 24v into the 12v systems...

 

[Robbyg]

After looking at the circuit for a bit I think it's a voltage reference circuit. Probably using some op amps to generate a low voltage reference and the rest of the circuitry is to both create the needed voltages for the Op-amps and to cutoff the ground connection if incoming voltage is too low or too high.

 

[Robbyg]

Ok well now that I can see some IC numbers and the Zener diode etc it's clear that it's a voltage reference board to prevent the charger from being powered if the line voltage is outside the set parameters. I have no idea what PHR85 is, I think some part of the number is missing but the AP4310 is definitely a dual op amp voltage reference.

Yes you probably could change some resistors and fool it into switching power on at a lower voltage but would you really want to do that?

 

[idiogenic]

Doesn't really sound like something I should eliminate from the system then, bugger!

 

[Cyberpower678]

Doesn't really sound like something I should eliminate from the system then, bugger!

Not to mention this board uses surface parts. Making the swapping of the resistor difficult to do with a soldering iron.

 

[Robbyg]

Doesn't really sound like something I should eliminate from the system then, bugger!

No, if they went to that much trouble you can be sure it's for a good reason. Just get a battery booster and that should work fine.

Rob

 

[SteveT]

Good idea, hadn't thought of that!

It's a bit difficult though, the second battery is not located anywhere near the engine battery and I'd have to bypass the battery isolator and ensure I didn't do something that was going to put 24v into the 12v systems...

Rig it from the isolator if thats where both positives meet,,, not sure what isolator setup you have thou.

 

[noone]

How about a $30 power inverter? I read about the DJI car charger needing the engine on to work and specifically avoided the Fly More combo because of this and the fact that I didn't like the bag. I instead bought 2 extra batteries and the charging hub and already had this type power inverter which works fine charging with the vehicle off when you need to. Obviously you don't want to do this for extended periods of time because you could drain your car battery.

Amazon.com: BESTEK 300W Power Inverter DC 12V to 110V AC Car Inverter with 3.1A Dual USB Car Adapter: Automotive

 

[Cyberpower678]

Wow, really? I need to try out my own car charger, and see if my battery can handle it.

 

[Egika]

Ok well now that I can see some IC numbers and the Zener diode etc it's clear that it's a voltage reference board to prevent the charger from being powered if the line voltage is outside the set parameters. I have no idea what PHR85 is, I think some part of the number is missing but the AP4310 is definitely a dual op amp voltage reference.

Yes you probably could change some resistors and fool it into switching power on at a lower voltage but would you really want to do that?

The other chip obviously is a Toshiba TPHR8504PL - a dual power MOSFET that is used in DC-DC converters or switching regulators as Toshiba advertises it: TPHR8504PL | MOSFET | TOSHIBA Storage & Electronic Devices Solutions Company | Europe(EMEA)
Now it depends on the external parts to it, what the input voltage limits are

 

[Dragonfly]

Thanks guys, here's some close ups.

I'm going to call this 'Side A':



It's a bit tricky to get a clear shot of Side B - the wires overlying the board don't really want to move.


Googling the IC on Side A gets me to this document:
https://www.diodes.com/assets/Datasheets/AP4310E.pdf

I know SFA about electronics, but this is making me think that the element inside the cigarette plug isn't just a simple thermal cutoff?

That's is a basic voltatage regulator with thermal overload. It will input a voltatage from 12 to 26 volts and output a steady 13 volts.

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