dual battery mod

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I got my first solo earlier this spring, and for being one of the most inexpensive drones, I think the hardware and software are as good or better than many of the higher end drones. The only problem is that it loses gps lock and controller connection randomly. The first one I had was not too bad, the gps would go out randomly, about once every other flight or so, and the controller signal was pretty consistent as long as it had good wifi signal strength. It however ended up in the gulf of mexico as a result of a flyaway after about 50 or so flights, and was kindly replaced by 3dr. The new drone was considerably less reliable, with a gps loss or controller signal loss at least once per flight. These errors would occur in the open with no obstructions to either the gps or controller.

The random nature of the errors led me to believe that it might be electrical noise, so I made sure all the wires and cables were securely attached. Everything looked good, and all the ferrite beads were in all the right places. Running powerful motors with computers and sensitive radio equipment on the same power supply seems like a bad idea, so I added a second lipo to isolate the sensitive stuff from the noisy stuff.

I soldered wires from the main battery directly to the four motor pods to isolate the high amp loads. The secondary battery shares a common ground with the main battery, and I added a circuit which connects the second battery when the main battery turns on, and disconnects it when the main battery turns off.

After the mod there have been no gps or controller errors, so it looks like noise from the motors might have been the problem. I'll post some pics and a circuit diagram once I get some more flight time.

Has anyone tried anything like this or any other techniques to improve reliability?
 
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This is the circuit for powering on the two batteries in unison. The switch at the bottom is to keep the control electronics powered on during flight, regardless of the state of the main battery. After the solo powers up and before it takes off, I close the switch. After landing I open the switch so the second battery is disconnected when the main battery turns off.

View media item 675
I have a 6 amp hour 4s for testing, but am switching to a lighter 1 amp hour for use with the gopro.

View media item 676
 
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I'm curious - how do the battery level electronics react to this? Does the meter on the controller stay on 100% longer, or does it just deplete at a slower rate?
 
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I was curious myself. It turns out that the solo only knows about the state of the original flight battery. It gets that info directly from the battery over a serial connection.

The second battery powers the computers and radios, leaving the main flight battery to only power the motors and lights. It could theoretically increase flight time, but with the extra weight its probably not too significant.
 
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The extra weight of that battery is going to be very very detrimental. The handing will suck, and the flight time will tank. That unfortunately will literally outweigh any other benefits.
 
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The extra weight is only about 100 grams over the gimbal and gopro. With the master airscrew props it handles just like or better than originally. But I completely agree, there is no need for a large second battery. A 1 amp hour would last over an hour.
 
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I hadn't even noticed there was no gimbal on there which makes up for the difference. What I said would apply to also having the gimbal and camera weight on there. A small 1 or 2 amp battery would probably be better, but expect a net reduction in flight time regardless.

Also, putting that on there is a HUGE point of failure now. If that battery or any component attached to it dies in flight, your solo is going down. A 1 amp battery is way too little for such a flight critical function. 2-3 would be better. But then the weight is back. If you're going to do this with a 1 amp battery, your circuit should automatically fail over to the flight battery if it starts getting low.
 
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I like the idea of a failsafe reverting to the main pack. The only reason for the second battery in the first place is to give clean power to the critical components, not to increase the flight time. However with the 6 amp hour I have gotten well over 12 hours of run time with the gopro and gimbal during non flight tests. So I am thinking the 1 amp hour would last at least 2 hours in flight, far surpassing the main battery by about 10 times.
 
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putting that on there is a HUGE point of failure
Before the mod, I didn't have a single flight without a major system failure, after it there have been none at all over tens of hours of testing. So as far as failure modes, this is probably not a significant concern.
 
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The draw without the motors running is 0.9 to 1.3 amps with no added accessories. So a 1 amp battery can't be relied on to last 2 hours.

I'm very surprised this resolved so many problems for you. Did you try powering the rest of the Solo with the flight battery, but with the motor pods wired up separately still? That basically removes the high current drive power from the carrier board and all the stuff around it.
 
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The 0.9 to 1.3 amps you are referring to includes the leds on the motor pods. That is still powered from the original battery. I will check the amp draw from the second battery sometime, but I am thinking the1 amp hour will suffice.

I did a lot of testing to try and diagnose the problem. Everything worked great as long as it wasn't in flight. But in flight the gps would randomly lose lock and the controller signal would randomly cut out. Electrical noise is very difficult to diagnose and remedy. The best thing is to start from a baseline of clean stable power, and then work from there.
 
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You are on to something for sure. Adding a second 40 cent Ferrite Ring Core on the GPS cable gets me 4 extra satellites. For some people that would be the difference between flying safe and crashing.
Super copper shielding the battery and GPS does nothing (tested on 3 Solos) because it just reflects the noise back on the GPS cable. The Pad v2 helps since it absorbs some of noise instead of just bouncing it back on the cable, in my opinion. Treating the symptoms and not the cause.

5 Pcs 3.5mm Noise Suppressor Clip Cable Clip-on Filter Ferrite Ring Core
 
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I hadn't thought about the number of satellites, because the gps lock would fail even with 10 or more. Before the mod where I usually take off from it would get a very consistent 6 or 7, now on the clean power it gets 8 to 9, so there is a definite increase in performance, not just reliability.
 
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Did you try powering the rest of the Solo with the flight battery, but with the motor pods wired up separately still? That basically removes the high current drive power from the carrier board and all the stuff around it.
The problem isn't that the motor power traces are physically close to the carrier board, its that they are electrically connected to the same power source. Rerouting the wires won't help with that.
 
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It would be interesting to see if this fixed the 3.3 vs 5v signaling problem on the motor pods that resulted in the PixHawk 2.1 Green.
Of course testing it might result in a crashed Solo. Too bad someone hasn't figured out a way to test/simulate the problem on the ground.
 
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This dual battery mod separates motor power from the computer power. It can fix reliability issues, but signal voltages will be unaffected, so it won't help with that.
 
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Yea but, with the Solo's battery rewired directly to the motor pods rather than passing through the traces on the motherboard maybe the "ground bounce" that was said to be responsible for the motors stalling would be reduced.
The signaling voltage change implemented Pixhawk2.1 Green fixed the problem by over voltageing the motor pod's PWM input.
Since there is no schematic of the motor pod publicly available it is hard to tell where the PWM input goes. (well I guess someone has reverse engineered it by now ;>) so some one knows).
 
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The signaling voltage change implemented Pixhawk2.1 Green fixed the problem by over voltageing the motor pod's PWM input.
Thats interesting. Sounds like this very well may fix the problem. It would depend on how well the motor pod electronics keep the signal side separated from the power side, but there is a good chance.
 
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I believe there is ground on the DF-whatever connector going from the carrier to the motor pods along with the signal and LED stuff. From what I can tell, they are not isolated. If you unplug the connector from the carrier, the LEDs stay on, getting their ground from the motor ground. Most ESCs do not isolate that stuff, so not surprised.
 

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