This could be big![emoji41]
I get a little frustrated working with this DJI battery manager. I find myself wanting to find the firmware designer and do really bad things to him. I don’t find myself cussing so much any more. It took a while, but my dignity is coming back now that I have left my catatonic, fetal position. The reports of thumb sucking, etc are greatly exaggerated, so please cut me some slack…
Yeah, ever notice how the transmitter shows you cell, voltage recovery when you land? The color goes either from orange or red back to green? Some of that is battery recovery, for sure. Some of it could be voltage drop if your wires aren’t of sufficient size while under load. The bigger the load, the more apparent this effect will be.
When I added the load of the equivalent of a second smart battery without the circuitry, the copter no longer flew smooth as silk. It became choppy and the transmitter voltage drop was more pronounced. Btw, the extended batteries are feeding directly to the ESC board, bypassing the battery manager, so the battery manager was getting an assist. Also, Btw, I didn’t attribute this behavior to voltage drop immediately, hence my replacement of the motors and downward spiral into catatonic, oh never mind….
I wired my entire bird using 14-gauge wire. Gauge chosen walking that fine line of weight vs capacity and the observation that DJI used 14 for internal connections. However, the DJI (presumably, highly engineered) connections were very short, less than an inch. Mine not, and sometimes as long as 6 inches. DC does not travel very well. Even 6 inches will make a difference. This is the very reason AC was developed, for long runs (Btw).
So, I re-wired using 10 gauge from Radio Shack (yes sir, I went in there) I have 12 gauge, silver plated strand ordered, that is what I am going to standardize on. I am also going to start to use 5% silver solder, rosin core. This is over-kill designed to hedge my bet to remove conductivity as an issue and find the middle ground on weight. So I will be re-wiring once again when I have everything. It is just as well, this test with the RS 10 G produced the new knowledge about how to run the battery manager in this new mode. It will probably influence my (hopefully) permanent wiring job.
So, guys before me, the ones whose shoulders I stand are the ones that have been extending flight successfully by connecting after the battery manager. Nobody bothered to document this fact, unfortunately. I spent months trying to extend trying to work with the battery manager. It is a lot easier being able to use the same switch, etc…. The reason this works, I speculate is the fact is that it is after the manager, and the manager doesn’t get to see the electron flow provided by the extension batteries. Electricity will always follow the path of least resistance.
OK, to describe a little better, in this context, what I discovered: I created a connection very similar to the connection the extended battery has after the battery manager to the primary battery. The connection must be left open normally, otherwise the copter will start up. The copter needs the battery manager to arm, however.
So, I start the copter the normal way and it arms itself and initializes. The amperage helping circuit is simply a male/female plug I just connect at this point. It is 12 gauge wire. Knowing that electricity is going to follow the route of least resistance, how would you guess the real power is going to flow? This is also going to take a load off of that poor battery manager. It should stay nicely powered to keep the copter armed and informed of the voltage?
Copter lands, I pull the plug and turn the copter off. I want you to note that I was able to, for the first time, use a single battery, a Hyperion HV 5200 that I split into two 2s’s wired in series and I was able to fly it down to 3.33 volts. Before this, I did nothing but cuss at China… There is no reason this wouldn’t be appropriate for dual battery configurations. My next wire job will just have a switch, I think. What do we call the switch? (The screw DJI switch?)