Just recently returned from Iceland where we drove the Island for 5 days.
It's the first time I had used the DJI car charger and it appeared to work fine except it
would not charge a battery over 86-87%
Tried starting the battery and re-pluging the charger. It appeared to due further charging, but still
only showed 86-87%.
Thought this was a bit odd.

Hi, can you try it on another car and see if it charges beyond that?  If not, please send an email to support.us@dji.com. Thank you.

I had the same when I used mine, I am going to attach a power supply socket direct to the battery and try it that way.

I have similar issues myself - I find my DJI car charger will run for a while and then stop at seemingly random intervals.

In my case I suspect the issue is related to modern car's alternator setups (e.g. Euro 5 diesels with "smart alternators"). Traditionally, the car battery voltage would be around 13.8 volts when driving but on my car this often drops away for significant periods of time as the alternator reduces the charge voltage to save energy (this is by design). Where it does increase the voltage significantly is when the car is going down hill or I am braking in which case regenerative braking kicks in and the voltage can get closer to 15V.

On a longer journey the DJI charger switches off prematurely as the car has dropped the alternator voltage to save energy. However, when I brake or go down a hill for any length of time, the DJI charger starts charging the battery again only for the duration of braking/going down a hill.

I suspect the DJI charger is set to cut out below a certain car battery voltage to prevent the car battery being discharged too far if the engine is not running. Maybe the cutout threshold voltage is too high on my DJI charger...

davidson_g Posted at 2016-8-6 02:40
I have similar issues myself - I find my DJI car charger will run for a while and then stop at seemi ...

Thanks,  this was a Ford Diesel engine.  Going to try on my F-150 gasoline.

DJI-H.C Posted at 2016-8-6 02:22
Hi, can you try it on another car and see if it charges beyond that?  If not, please send an email t ...

Yes, I will.
Thanks

DJI-H.C Posted at 2016-8-6 02:22
Hi, can you try it on another car and see if it charges beyond that?  If not, please send an email t ...

Charged one in my pickup and it worked fine.  My problem appears to have been with the rental car.

davidson_g Posted at 2016-8-6 15:40
I have similar issues myself - I find my DJI car charger will run for a while and then stop at seemi ...

You are not charging your Phantom directly from the alternator.   You are charging it from the battery.    Turn the car off and the battery will still power your charger if your cigarette lighter is wired to be active when the key is off.

Maybe you are using an DC to AC Inverter plugged into the cigarette lighter?   If so, make sure you are using a high quality full sine wave inverter.  Many are half wave and don't produce clean AC voltage.  That would do it.

If you have a weak battery, this could happen.   
Measure your cars battery voltage in the morning, BEFORE you've  run the car for the first time of the day.   If voltage is below 12.7 you either have a drain or a weak cell(s).    I would disconnect one battery terminal the night before the test to get a true reading.

davidson_g Posted at 2016-8-6 08:40
I have similar issues myself - I find my DJI car charger will run for a while and then stop at seemi ...

Exactly the same here, I have a volt meter and it quite often drops to 12 volts when running and the charger stops charging, like you say a modern car has all sorts of intricate electronics and not just an on off charging system, I am going to try and use the charger on a stand alone car battery see what happens, as it's quite annoying I can't charge my p4 batteries from the ciggy lighter socket

davidson_g Posted at 2016-8-6 08:40
I have similar issues myself - I find my DJI car charger will run for a while and then stop at seemi ...

Exactly the same here, I have a volt meter and it quite often drops to 12 volts when running and the charger stops charging, like you say a modern car has all sorts of intricate electronics and not just an on off charging system, I am going to try and use the charger on a stand alone car battery see what happens, as it's quite annoying I can't charge my p4 batteries from the ciggy lighter socket

Cessna172 Posted at 2016-8-6 17:45
You are not charging your Phantom directly from the alternator.   You are charging it from the bat ...

I'm using DJI's P4 car charger which runs directly from 12V - the problem is that it's designed to cut out at a voltage DJI deems to be safe to allow the car to start should it be left plugged into a accessory port that works with the ignition off. (annoyingly my car kills the accessory port a few mins after the engine is stopped or if I open a door!)

I'm tempted to do an experiment to find out what the exact cutoff voltage is as I have a nice variable voltage 20A lab PSU in my workshop I can test this with. The manual with the DJI charger suggests that it may be 12.3 volts. One factor could also be how much voltage drop there is between the car battery and the charger itself given that it must be pulling about 8 amps (90watts) which is significant. At that current I might be losing enough voltage across the wiring to bring a worst-case 12.5V battery terminal voltage to below 12.3 volts at the charger itself.

The problem with Euro engines is that they are using all sorts of trickery to increase efficiency, one of them is not to charge the battery fully. My car is a stop-start diesel and has to cope with an engine start each time I pull up - which it does flawlessly Under acceleration, or times when the engine is not at it's most efficient, the alternator may even allow the voltage to drop to 12.5V

Here's an interesting article on the subject - it's giving trouble to those who want to charge auxiliary 12V batteries.

http://www.12voltplanet.co.uk/au ... rt-alternators.html

Snowwolfwarrior Posted at 2016-8-6 19:26
Exactly the same here, I have a volt meter and it quite often drops to 12 volts when running and t ...

That should be interesting!

I wondered about a standalone car battery too - I reckon if the car battery is fresh off a charge, the terminal voltage will be sufficient to allow the DJI charger to run a while. What I don't know is how quickly the car battery voltage will drop over the course of time - depends on the design capacity of the battery (Ah).

Apologies if I proceed to bore your socks off with numbers....

If 12.3 volts is the minimum required to operate the DJI charger, that equates to a cell voltage of 2.05 volts  (6 cells in a 12V battery) which according to some Lead Acid discharge curves I'm looking at could equate to ballpark 70% remaining car battery charge before the charger cuts out. Then there's the issue of voltage drop on the cables between the battery and the DJI charger - 8A is quite appreciable.

Will be interested to hear how you get on with the stand-alone battery!

davidson_g Posted at 2016-8-7 03:04
I'm using DJI's P4 car charger which runs directly from 12V - the problem is that it's designed to  ...

ok.  You need another battery.   One that charges fully....and a solar panel?
They are available in 12v versions.  100watt should work fine.
Heck, you could even connect the solar panel directly to the charger if you use a voltage regulator.

And since you'll probably never be out flying in bad weather, you should always have enough light.

The other option is to get multiple batteries of course...or a small FULL SINE WAVE generator like the Honda Ei2000

Cessna172 Posted at 2016-8-6 20:44
ok.  You need another battery.   One that charges fully....and a solar panel?
They are available  ...

Thanks for all the the suggestions  - much appreciated.

Fortunately after discovering my charging problems I bought a third P4 battery to help tide me over.

Admittedly due to the time it takes for a P4 battery to charge, I did find it a bit impractical to charge a battery via the car unless I had about an hour journey to my next flight. A car charger seemed a good idea at the time until I tried it out.

The solar panels sound great but I don't have a big enough vehicle to accommodate the extra gear in a convenient way that allow the batteries to charge unattended whilst I'm flying on the other batteries. An ideal solution could be a solar roof rack with on board lead acid batteries.

The Honda's a quality generator but I see it's quite expensive which on balance probably makes additional P4 batteries more cost effective.

It's a tough call but extra P4 batteries seems to be the answer for the typical half day trips I make. I think if I was away from civilisation for a few days, there would be a much better case for solar panels or the Honda.

Thanks again

Same issue but solved it by turning on my head lights so that the car is taking more power from the battery this makes the smart alternator produce more voltage... I think

I had also faced the same problem when i bought a new charger. However, there was a issue with my car battery. Charger was working good with other batteries. So Try to change the change.

I'm having trouble equating this smart alternator with battery voltages quoted ...

Once a cars battery is charged - the alternator will only supply support current to allow other items such as radios / lights etc. to function fully. The alternator on near all cars never actually shuts off because that blows it bridge diodes .. ask any boat owner why he has a Make before Break power switch !

The Ciggy socket should have the full voltage of the battery less any voltage drop of course .. and if alternator is running - which are usually rated at over 14.5V but variable amps depending on charge reqt's - the ciggy socket should show that.

I have to say that my Volvo XC70 has a 12v socket in the back that runs straight of the battery under the cargo floor - so I get full whack through my P3 car charger ... I admit mine is not DJi - its an eBay item and never failed to full charge.... with engine on or off.

I'm just trying to reconcile that a motor manufacturer would deliberately cause items not to work via the ciggy sockets ....

Nigel