Mid-air BT-300 system shut down 'USB CHARGER ERROR' - HELP!

[bmelody]

David,

I got to thinking about your situation last night. Originally we thought error was caused by overheating of the battery due to the controller charging. While the charging issue is something I feel should be addressed it may not be what's happening in your case. I was able to duplicate the "USB CHARGING ERROR" but in my case it was due to a low voltage being supplied to the BT-300's. My BT-330 was not hot during my test. The batteries in both units were approximately 50%. The error occurs when the voltage falls below approximately 3.5VDC. It takes about 23-30 seconds for the error to appear once the voltage drops. Your problem may in be in the MA controller or cable as previously suggested by EpsonMoverio. You may have an intermittent connection or a too high/low voltage when connected to the MA.

Do you have a way of measuring the voltage coming out of the MA controller?

Were you using the same OTG cable when switching controllers?

Do you have another cable you can try?

I could build you a test cable with a resistor if you would like to try one. It won't be pretty but it will be functional and safe to use.

When you switched to the other monitor to continue flying the MA did you use the same OTG cable?

~Bill

 

[Davo_101]

Yes - I agree - last tests I did were in the house from cold with MA tx so I don't think it is temperature related.

Do you have a way of measuring the voltage coming out of the MA controller? I have an app that shows charge rate and voltage of BT-300 battery but not the voltage from the controller.

Were you using the same OTG cable when switching controllers? - yes it's a high quality Anker cable - I got frequent GO disconnects with the original.

Do you have another cable you can try? - yes - several but not of high quality as above.

I could build you a test cable with a resistor if you would like to try one. It won't be pretty but it will be functional and safe to use. - fantastic - I have dropped you a personal message.

When you switched to the other monitor to continue flying the MA did you use the same OTG cable? - yes same cable.

 

[bmelody]

I got your other message and responded.

Something new I discovered today when flying the spark. I started out with ~75% charge on the controller. Everything appeared normal and I flew 2 batteries ~22 minutes and the controller continued to charge the BT's. I recharged the flight batteries but not the BT's or the controller. I flew 2 more batteries for an additional ~22 minutes. At this point the controller was down to 50% (2 of 4 LED's) but I noticed the BT's were no longer charging (LED's not flashing). So at some point the charge current was reduced possibly by DJI's firmware in the controller. I doubled checked and there was no charge indicator and the battery in the BT was at 33%. I never got a USB CHARGER ERROR and everything functioned as it should. I was not aware of any change everything was transparent.

Well that theory just went out the window. I allowed the BT's to cool down as they were quite warm, did not charge anything and simply switched everything back on. Everything booted as expected and the BT's started charging again. So it appears now that the BT's sensed the battery temperature and shut down the charge until they cooed down a bit. Perhaps this is correct by design and we really need the Moverio engineers to clarify the charging conditions for us. If this assumption is correct you may have a bad unit and may require replacement.

Totally confused now,

~Bill

 

[Davo_101]

Very interesting - I am going to give it another try and if I get the error again I will initiate a return. Good job I purchased with Amazon Prime that should make it easier.

I hope we will get some response from Epson but I am not holding my breath.

Thanks again. David.

 

[bmelody]

Hello again David,

Today I decided to try my MP with the glasses and an OTG cable. I go the dreaded USB CHARGER ERROR using 2 different cables. I was able to get it to clear using a 3rd cable. I could recreate the error going back to either one of the other cables. Using the 3rd cable I was able to make a complete flight with no errors. I can also create the error by lowering the charge current to below 20 mA. At that point the voltage is to low and the BT's go into error. At 40 mA and above the unit preforms just fine. My MP is charging the same at the same rate as the Spark, approximately 450 mA. It appears the cables do have a lot to due with the error. At 450 mA the voltage drop using the light gauge wire may be more than BT's can handle. I think I may abandon the OTG cable and go back to WiFi. Never had an issue and the BT's run cooler. If you can try several different cables you may get lucky. But the error is caused by too low a voltage reaching the BT's. Also the problem is less sensitive when the BT's have a charge higher than 30%. So when you first discovered the problem internal battery in the BT's may have been below ~30%. This problem would go away if Epson Moverio gave us the ability to turn off the charger. Perhaps they could lower the charge current via software whenever the DJI GO app is running.

The test cable I made with the resister and lowering the current to 40 mA seems to work just fine. I can send it to you for a test if you are still interested.

~Bill

 

[Davo_101]

Tested again - hovered in garden for 12 minutes - checked Ampere and there was an overheat warning and temp was at 47C at 88% battery 4.1v - went back to GO and a minute later the USB error popped up and the system shut down. Perhaps if I strap on a freezer pack I could get a whole flight in! I am really hoping your cable works to reduce the charge temperature ...

 

[bmelody]

Very interesting. You sent me a private email yesterday and I responded. Did you get my response? I need additional information from you and I have some additional information for you and want to make sure we have a link.

 

[bmelody]

All,

It appears I may have rushed to an incorrect conclusion on the battery temperature rising when the BT’s when connected to any DJI controller via an OTG cable. I ran a more detailed test and listed below are my results.

1. The BT’s draw approximately 1250 mA when fully booted and the DJI GO app running. Based on the results from the Ampere app.

2. The DJI controller is current limited to supply up to 450 mA. Measured using an external DMM.

3. The temperature of the battery in the BT’s actually rises when NOT connect to the DJI controller. Based on the results from the Ampere app.

4. When the BT’s are fully dependent in its internal battery the temperature of the battery increases. The actual amount of increase is determined by the length of time the unit on.

5. When the BT’s are up and running and connected via an OTG cable the temperature of the battery will actually decrease. This is due to 450 mA of the total current demand is now being supplied from the DJI controller. This reduces the strain on the BT’s internal battery by almost ~ 1/3.

6. There will be a reduced amount of run time on the DJI controller when connected via an OTG cable to the BT’s. However the DJI controller appears to have an ample amount of reserve so it should not be a big problem.

7. Using an OTG cable will increase the run time of the BT’s by approximately 1/3 due to some of the required power is coming from the DJI controller.

8. The BT’s do have an internal control that will power down the charging circuit when the battery gets too hot. At some point the charger comes back on.

9. When charging, the 450 mA from the controller is divided between powering the device and charging the battery. I cannot determine split without disassembling the BT’s. However the Ampere app does indicate the battery is being charged. The firmware in the BT’s appears to monitor the charge rate, voltage, temperature and health of the battery. It is also switches the charging circuit on and off from time to time. I could not determine if the switching was dependent on time, temp or voltage but the BT’s are indeed monitoring the charge cycle to some degree.

10. I built a cable that allowed me to decrease the amount of current supplied by the DJI controller but in conclusion all that did was increase the run time for the DJI controller, decrease the run time of the BT’s and worst of all, it increased the overall temperature of the BT’s.

11. At one time I thought DJI should decrease the current limit available at their USB port but that to would increase the temperature of the BT’s. This is not a viable solution proved by using my current limiting cable.

12. My next experiment will be to run the BT’s from an external power pack capable of a slightly higher output current to see if further lowering the demand on the internal battery will help decrease the overall temperature.

13. I am also going to experiment with a small fan to see what effect it has on the overall temperature.

14. At times, on the bench, not in the air (for me anyway) I would get a “USB CHARGER ERROR” shutdown in 30 seconds. This is not a comfortable thing to have happen, but better than a total shutdown without any warning which has happened to others. I believe (not yet verified) USB charger error happens when the BT’s battery is below 30% and a charger is connected and/or a DJI controller is switched on. For some reason the inrush current causes some confusion and the BT’s shutdown. Unfortunately this was not repeatable so it is only an assumption. Hopefully there is something that can be addressed via software and/or firmware. It wouldn’t be so bad if the pending shutdown could be cancelled but once initiated in 30 seconds the BT’s will shut down.

For now it’s back to the drawing board, sorry if I miss led anyone. But as Thomas Edison once said, “After 999 attempts to make a light bulb that did not work we now know 999 ways how NOT to make a light bulb”.

~ Bill

 

[Davo_101]

Thanks again - great research - I hope this gets sent to the engineers to give them more information.

I will let you know how this works out for me - still trying to figure out which one is at fault, the BT-300s or the Air TX. I really don't think it can be the Anker cable but will continue to experiment with a variety of others.

 

[jesswin]

Just want to add my name to the list of Mavic Air users with USB CHARGER issue. Today, about halfway thru a second battery, I got the error. I switched to third battery and after several minutes got the error again. I can't add much to diagnostics at this point but will keep in touch if can identify any pattern.

 

[bmelody]

Just to add some additional information it is not just the Mavic Air I can get the same error with my Mavic Pro, and Spark.

 

[bmelody]

Some additional data.

Earlier I thought the DJI controllers were limiting their output current to 450 mA. Not so the BT's are limiting the charge current internally. Running the BT's from a lab supply capable of several amps the BT's maintained a constant draw of 450 MA.

I ran another bench test with the BT's running DJI GO app and connected to a Mavic pro controller. The Mavic was on so there was some video being processed. The ambient (room) temperature was 20 degrees C, 68 degree F. After approximately 30 minutes of operation the BT's generated an OVER HEAT error and shut down charging the internal battery. The battery temperature was 47 degrees C. I put a small fan blowing at the back of the BT's and within 12 minutes the battery temperature dropped to 32 degrees C.

I recharged everything and ran another test. This time I kept the small fan on from the start. The starting temperature was 26 degrees C and after an hour of running the max temperature recorded was 32 degrees. It reached the 32 degree mark after 22 minutes of on time and remained there until I stopped the test.

My next thing will be to incorporate the fan into a holder to see if that will help keep the BT's cool enough to prevent any shutdowns.

No "USB CHARGE ERRORS" during any of the tests.

 

[Davo_101]

I have purchased a cheap USB computer fan that I have attached to the Moverio mount with elastic bands. Powered by an external power bank. A bit Heath Robinson but I think it should work. Will test and post up a photo. @bmelody Thanks for the inspiration ...

 

[bmelody]

Hi David,

Attached is a picture of how I mounted the test fan to my holder yesterday. In my case I removed the web in the holder that divided the area under the BT''s. I did this to create one long channel. The slight spacing between the fan and the BT's creates a duct for the air to flow. Be sure when you mount your fan there is a place to allow the air to flow and the exhaust to escape.

I ran another 1 hour bench test and the temperature never exceeded 32 degrees C. I hope your results are as good as mine.

I may test fly it today.

~Bill

 

[Davo_101]

I think I need a smaller fan

 

[DVegaman]

Wow, that is like a box fan! If that doesn't keep it cool, nothing will. Nice job.

 

[Davo_101]

More Power!

 

[bmelody]

Looks like a perfect test platform.

I just had to move the location of the fan due to an interference with the USB connector on the controller. But this may be a better location because it is directly over the hottest part of the BT's.

 

[bmelody]

I ran a bench test using a fan attached to my BT mount. I powered the fan from the DJI controller (approx 250 mA) also had a 20 ohm current limiting resistor is series with the BT's. This combination may not be the optimum configuration. Decreasing the value of the current limiting resistor may decrease the battery temperature but will decrease the operating time of the controller. I believe the current configuration would provide ~90 minutes of operating time while limiting the BT's temperature to 33/34 degrees C.

After disconnecting the fan the battery temperature started to increase. After 30 minutes of operating without the fan the BT's battery reached a temperature of 45C and the Apmere app reported a BATTERY OVER TEMP. The charging was discontinued however the temperature continued to rise. The BT's temperature would have continued to rise and shut down if I had allowed them to continued to run.

Test results:



The BT current readings were provided by the Ampere app and are an approximate indication of current flow however I find the reading somewhat confusing at time. Where there is a major in crease in current at 12:50 in time it was when I switched to the BT's to display the DJI app. Apparently the power demand increases when there is a lot of video processing going on. This would decrease the the BT batt remaining percentage slightly form the numbers recorded above.

Clearly the fan makes a big difference in operating temperature.

I wonder if a new back cover for the BT's made from aluminum would help dissipate the heat? Maybe just adding a simple heatsink to the back case would reduce the temperature enough to stop the shutdown and or USB Charger Error?

Sadly I have not heard anything back on my emails directly to Epson as to any of my findings and or possible solutions.

Also sad none of the Moverio guys that monitor this site have not commented on any of the problems, test results we have posted.

~Bill

 

[Ken Nash]

Bill, I don't fully understand everything you have written, but sounds right to me, in essence I think your implying that the harder the DJI Go App works and the more you ask from the controller it gets hotter therefore the more likely the controller will shut down. But great report all the same.