Tablet charging while connected to the Remote

JimPA · May 11, 2015

I'm using a Nexus 7 (2013) and it runs fine and works well. However, it doesn't seem to change very well when being connected to the remote. Acts almost like it doesn't charge at all. It does show the lightning bolt in the battery icon so it does detect charging, but the tablet's battery runs down so quickly. I may only get 3-4 flights before the battery on the tabled is dead.

I'm thinking of making a small 5V 2A charging circuit that will allow me to top it off directly from one of the Inspire Batteries prior to flight. I have 4 Inspire batteries, but don't normally use more than 3.

SteveT1 · May 13, 2015

Try this.....
http://www.smartpowercharge.com/proddetail.php?prod=SPC17
or you could by a separate battery
http://www.ravpower.com/ravpower-23000mah-portable-charger-external-battery-charger.html
This one may be a little overkill but they make smaller ones, I use it to run my HDMI display also

BTW the RC does not charge anything connected to the USB port

kenny kustom · May 13, 2015

My remote charges both my phone and my iPad..

Sent from my iPhone using Tapatalk

JimPA · May 13, 2015

Ok, I did some experiments today. The RC DOES charge whatever is connected to the USB port, but only at the lower USB levels of current. While connected the RC will only allow the USB to pull ~450mA. I made a 5V 2A charger that can run off of one of the Inspire batteries. It works the same and will only charge the tablet at the same ~450mA.

I found this is a limitation of the tablet. I connected to a 2.1A AC USB Charger. When connected to this one the tablet will pull ~1,100mA. I'm assuming this is to the USB Spec that says a device needs to talk to the USB port and ASK for permission to pull more current. My simple charger I built is rated for 3A, but will only provide that if the device connected pulls that. Since I don't have the protocols to have the conversation with the tablet for it to ask for more current, it only pulls the default ~500mA.

I'm assuming the DJI RC does the same thing. It does use the USB for communications, but doesn't allow the tablet to pull anymore than the default ~500mA.

I have a 6600mAh portable USB battery. It does allow the tablet to pull the 1,100mA when charging. I guess I can carry that and put the tablet on there in between flights.

The Editor · May 15, 2015

You is right! The RC WILL charge but only at the lower spec 500ma.
Since DJI didn't put in intelligent power management they have limited the charge current to avoid someone plugging in somethin from the Jurassic period and exploding in a fireball. Strange, since only modern spec devices are supported but hey ho.
It appears from reports on the forum that SOME devices will go into charge at 500ma supplied and some won't. The iPads of the world seem to not like a lower current while many of the Android tablets will go into a top-up or 'trickle' charge. This lets the battery last a little longer and not deplete quite so quickly on some tablets.
I have noticed on my Nvidia that the battery level drops quite quickly to around 76% and then drops more slowly after that.

Eduardo · Jun 17, 2015

The Editor said:
You is right! The RC WILL charge but only at the lower spec 500ma.
Since DJI didn't put in intelligent power ma.pavement they ha e limited the ish charge current to avoid someone plugging in somethin from the Jurassic period and exploding in a fireball. Strange, since only modern spec devices are supported but hey ho.
It appears from reports on the forum that SOME devices will go into charge at 500ma supplied and some won't. The iPads of the world seem to not like a lower current while many of the Android tablets will go into a top-up or 'trickle' charge. This lets the battery last a little longer and not deplete quite so quickly on some tablets.
I have noticed on my Nvidia that the battery level drops quite quickly to around 76% and then drops more slowly after that.

Is there a way to stop the controller from charging the tablet?

VAP · Dec 2, 2015

The Editor said:
You is right! The RC WILL charge but only at the lower spec 500ma.
Since DJI didn't put in intelligent power ma.pavement they ha e limited the ish charge current to avoid someone plugging in somethin from the Jurassic period and exploding in a fireball. Strange, since only modern spec devices are supported but hey ho.
It appears from reports on the forum that SOME devices will go into charge at 500ma supplied and some won't. The iPads of the world seem to not like a lower current while many of the Android tablets will go into a top-up or 'trickle' charge. This lets the battery last a little longer and not deplete quite so quickly on some tablets.
I have noticed on my Nvidia that the battery level drops quite quickly to around 76% and then drops more slowly after that.

Will the ipad be able to run at all with the charge? I am testing it now and the IOS is running down even as I have a battery hooked up to the RC which is charging.

Kilrah · Dec 3, 2015

The iPad will "charge" but as it's still using more than what the RC can supply battery level will still decrease, just a bit less quickly.

fluxkompensator · May 4, 2016

I am using an iPad Pro 9,7 and I am very unhappy about the battery being empty very fast..

I wonder, if it is possible to charge the pads from an other battery, a juicebox f.e. via a usb hub or a y-cable
while the tablet is hooked up with the remote..

I dont really have a clou if this is possible..

The Editor · May 4, 2016

fluxkompensator said:
I am using an iPad Pro 9,7 and I am very unhappy about the battery being empty very fast..

I wonder, if it is possible to charge the pads from an other battery, a juicebox f.e. via a usb hub or a y-cable
while the tablet is hooked up with the remote..

I dont really have a clou if this is possible..

How fast is 'Fast'?
I use an iPad and I flew six packs today back to back and was airborne for over 104 minutes. Both the remote and the iPad were on the entire time (I did not shut down between flights or close the app). With my pre and post flight checks the RC and iPad were up and running for around two hours continuous whilst also running the app. Screen was at full brightness as was volume.
At the end of the session the iPad had 74% battery!

JimPA · May 4, 2016

Not 100% sure, but I think you could create a special cable that only passes the ground and data lines of the USB cable from the RC to the IPad. A second power source that can charge at a higher rate than the 500ma the RC provides could then be connected to the IPad giving just ground and power. Only issue I see, is both the RC and charger would need data connected and that is probably the big issue you'd be running into. I guess a special charging circuit could be used that does not require the USB data lines to enable the higher current.

fluxkompensator · May 6, 2016

Hi Editor.. Hi JimPA..

I tested again yesterday.. Starting with 100% battery on the ipad I worked for 3 hours with the go app on all the time.. I ended with 25% left on the Pad.. That means max 4 hours on the pad.
That is pretty ok, but charging is taking ages! 4-5hours..

If I have a long day working that could be a bottleneck.
Would be great to avoid that hassle and have an easy solution to be able to hook up one of my old lipos on a DC/DC converter in parallel if needed without messing round with plugging..

Do you think the device and the charger "talk" to each other over the signal line? I tought it is just 5v on one line and the device is taking the amps that it needs to charge..

JimPA · May 6, 2016

Most USB devices try to take what they are given, but the USB spec is pretty low until the Device and Host establish what is ok. Many motherboards (where USB was designed to be used) limit the USB current to something like 50-100ma initially. The older USB spec was something like 500ma max. I'm pretty sure the RC will never allow more than that 500ma to be sent to the device and this is why on some tablets it will be a losing battle. If you look further up in this thread, I listed what I found when I hooked up a device that showed the current draw allowed when using my Nexus 7.

Like I said you could try rig up a cable that would separate the 5V from the RC and the tablet and try to insert an extra battery type charger but only connect the ground and 5V to the tablet from this source. You need to keep the ground and Data lines connected from the RC to the tablet for it to work. By making a special Y cable you could then try to get the tablet to charge from the other source that MAY allow higher current to get to the tablet.

All this is something you should try ONLY if you know what you're doing. You could easily blow up your tablet and/or RC if you get it wrong.

fluxkompensator said:
Hi Editor.. Hi JimPA..

I tested again yesterday.. Starting with 100% battery on the ipad I worked for 3 hours with the go app on all the time.. I ended with 25% left on the Pad.. That means max 4 hours on the pad.
That is pretty ok, but charging is taking ages! 4-5hours..

If I have a long day working that could be a bottleneck.
Would be great to avoid that hassle and have an easy solution to be able to hook up one of my old lipos on a DC/DC converter in parallel if needed without messing round with plugging..

Do you think the device and the charger "talk" to each other over the signal line? I tought it is just 5v on one line and the device is taking the amps that it needs to charge..