Yikes! I would not fly with those wires melting the velcro like that.
I really think 2 batts is too little for the current required here, at least with 10 awg. 4 would be so much better and halve the current each pack sees.
The suggestion for a ground test is a good one. Do you have an IR temp gun? I would run it up on the ground simulating a hard flight. Periodically checking cell temps. That is the big thing we need to be sure of.
Thank you everyone for your responses! When I am taking off I only need half throttle to pop up quick. But then I struggle to get above 100-200 feet. Now it’s making sense if I understand you all correctly… the resistance is increasing rapidly in the wire because of the temperature increasing rapidly in the wire and therefore I am losing voltage and RPM.
My battery wires are 10 AWG and ALL of the current is running through 2 wires (plus the series connection). My wiring harness is 8 AWG which is much better but also only has to handle a fourth of the current because they split out to 4 speed controllers. So, is there a need to shorten my wire harness up? I wouldn’t be able to take more than an inch or two out of each wire. Also, is it bad to have longer wires going to the left speed controllers and shorter wires going to the right speed controllers? The battery wires are certainly the weak link here, right?
Question: Did my batteries get even hotter than they would have because the wire resistance went down (due to heat), voltage went down, and amperage went up?
I’m feeling like Bonka messed up our entire group order! Paul said his came with 8 AWG while our group buy all came with 10 AWG. These batteries weren’t exactly cheap! So, now are we all expected to do lipo surgery to fix a manufacturing issue?
I would not cut the lipo up to change the wires. That will be very difficult to solder. The cells and size of wire will conduct a lot of heat away from the iron. One has to be very careful when soldering to batteries to not heat the cell up too much. I strongly discourage this.
My honest opinion: I think using only 2 batteries maybe insufficient, at least with 10AWG wire, for the use case here. Asking 300 amps of 10 AWG wire is not good. I know Paul is successfully flying it, but we don’t know his use (amount of climbing, etc.). Adding 2 more packs in parallel would solve all of these issues and halve the current each pack sees.
So, is there a need to shorten my wire harness up? I wouldn’t be able to take more than an inch or two out of each wire. Also, is it bad to have longer wires going to the left speed controllers and shorter wires going to the right speed controllers? The battery wires are certainly the weak link here, right?"
Taking an inch off won’t help much. They are just too small (the battery wires). It will not matter that one side is longer either for the ESCs; insignificant. You are correct that the battery wires are the undersized ones here.
The XT 150 connectors that came in the kit don’t have side cutouts to assist with soldering so we struggled to get a good solder joint (specially soldering to such big wire). Therefore, my confidence in that connection isn’t that great. I feel good about the rest of my connections though. Perhaps my next step will be to drill a hole in the side of the connector to see if I can get a better solder joint through that hole. Should I use lead based solder because it melts at a lower temp to get a better connection? Or, should I not use lead because of the fear that it will become unsoldered in flight? Could a bad solder joint there be the root of my problem with the wires getting so hot? I’m thinking it’s a combination of that and the wire size.
Use leaded solder. If they are getting so hot to melt the solder, you have big issues that need to be addressed. You may need a high power iron to solder those correctly as so much heat will be wicked away. You are wise to make sure your solder joints are good, though.
If the connector is getting hot, then yes, that would be a problem. Else, if it is just the wire getting, that is the problem. The heat will indicate where the losses are occurring.
Hey guys. A couple things:
I have borrowed a FLIR handheld and will be using it to check for hot spots and temperatures in my setup. Will post results.
To get good solder joint on my XT150s I actually used a pipe soldering blow torch very gently 
it gets the connector nice and hot definitely no issue with bad solder joints! Even my high power Weller iron couldn’t solder it otherwise. A bad solder could definitely make your wires hot!
@pdwhite is using Bonka’s with 8AWG wires (not 10 like us). From what I understand the 10AWG wire change was unexpected - I think we should wine to Bonka!!
Sorry to hijack Lukas’s build, but I think we really need to clarify somethings here. I consider it an important safety issue. If this should be made its own thread, we can do that!
@Pdwhite, can you confirm with us again the peak current the OpenPPG can draw at full throttle?
If that is truly 300 amps, then 10AWG won’t cut it on a 1P configuration for any length of time. I think there is a real risk of insulation failure if a pilot were to go full throttle for an extended period. That could prove catastrophic.
It is reasonable to expect that people will use this to climb as fast as possible for the whole pack and then glide down.
I do not have any data, I am just going on the statements made here. It is imperative that the wires be sized right. There were a lot of fire concerns when this project was announced, I want to make sure that never happens!
Ya for sure no one wants any melting stuff. I’m going to talk to Bonka about the wire size and see what’s going on. In the meantime if you want to run full throttle for extended time I would use two sets of bonkas. Or the other option is to run another wire in parallel along the batteries so it doubles the current and cuts out any heating. Peek currently can go above 300A maybe 340A on the initial throttle up for a few moments then drops down (that’s normal) so if we want to be extra safe we could over rate it to say 400A that way there plenty of room for safety?
@Lukas, I don’t know if you saw my post about shortening the 10 AGW battery wires down to under 3 inches but I just flew with 4 Bonka’s for 26 minutes and the wires were cooler than the batteries after I landed. The main reason I shortened the wires was to keep them well away from the props. Also, I didn’t have that drop in power that was noted before when I used only 2 batteries.
Same here.
A little bit of wee came out tonight when I arrived home to find my kit on the doorstep.
A six pack of beer, phone on silent and straight to the shed. Here are my impressions so far:
First up- Massive hats off to the creators of the kit. The further I got into the build, the more effort I could see that went into bring this to us. So thanks guys. Putting together that B.O.M for delivery must have been epic.
So far the carbon is spot on. Everything lines up just as it should.
Some of the 3D printed parts show signs of the printer shitting itself - others are very good. Nothing a bit of filing couldn’t solve.
Stepping through the video, almost frame by frame, made the mechanical assembly pretty straight forward (so far). I’m personally pretty confidant with the electrical side of things. Just like an oversized drone.
Tough bits so far:
The tolerance’s between the J-Bar arms and their mounts are super tight out of the box. A quick touch up inside the J-Bar with the Dremel and high grit sand finish and it’s perfect.
Also needed to purchase 16 x M3 - 15mm bolts and nuts to mount the ESC’s.
Well. That’s as far as I got tonight.
My work is sending me to remote outback Australia for the next 2 weeks, but can’t wait to get back and continue the build. Just a pity it wasn’t done and I could take it with me - would have made for some killer video.
I placed one lipo bag inside another identical lipo bag - found them at HobbyKing.
Lukas, two of your casings would probably fit inside the zipped bags - would be tight though - to be experimented with… If the two zippers must be closed all the way then small slits must be made to the side wall(s) to accommodate wire passage. I used one PG strap to secure the whole thing. It is solid. Two additional Bonkas + bags will also fit beneath the top assembly and 3 PG straps next to each other could also be used to secure the additional load. The straps simply wrap around the dorsal section of the frame between the harness backrest and the carbon fiber. The weight distribution is very good. The velcro attached to the outer lipo bag in addition to the thickness of the bags themselves provides enough material to negate the thickness of the frame’s screws. The screws are velcro covered anyway (hook side) and the material is tough, providing additional resistance to abrasion/perforation.
@Voltair, take a look a the thread on wire currents. If you’ve got 10 AWG wires on your batteries, you may want to be careful about wire Temp.
I will Luka. Thanks for the advice.
Hi, I read the section you recommended. How are you going to manage your wire harness/connections/temps. etc…? Thank you.
So,I’ve been thinking about this power switch and some of the challenges that people are facing with it.
Now, I’m tempted to just do away with it, but had an idea to try first before sending it to the bin.
I pulled it apart to take a look at what could be going on.
See the concenteric circles on the terminal contacts. There your contact patch to the 2mm Bus bar. Not much material for 300 amps to conduct through.
Thought I’d braze them with some solder and file flat to increase conductance area.
I also added an additional 2mm thickness to the copper bus bar that is the joining link in the switch circuit by brazing on another bit of copper the same size. Sorry - no pix of this bit as it was a bit of a ■■■■■ to reassemble and I didn’t want to take it apart again to photograph.
I’m hoping that this will increase the current rating of the switch, though it does face potentially fusing itself shut with the addition of solder in there. Testing will see…
To counter this, I’m using 8mm anti-spark battery connectors (an off-the-shelf pre-charge solution) and will run the switch in the always ON position. Unless I have reason to have to switch it off to isolate battery power.
Below is a pic of my power distribution setup.
Am currently printing plastic enclosures for the bus-bar terminals. Heaven forbid any of this should party with the carbon…
Will pull the switch apart after some load testing to see how it’s holding up. Stay tuned…
PS - Just noticed that this forum censors your word-choice based on what it thinks is is offensive.
Don’t get me started on censorship ■■■■.
Really curious to see what happens with your switch! I’d be a bit concerned about the solder melting in a high heat situation and the switch soldering itself shut
After a few flights, please take your switch apart and send pics!
What is the resistance of your pre-charge resistor?
I am thinking the anti-sparks will suffice. But I would also like to understand the raised circles on the connectors. My understanding of electron flow is that they like to travel on the outside edges of the wires, thus the more wires you have in the same size gauge conductor the better it lets electrons move. Maybe the raised circles emulate more wires?
Cheers, Patrick
oh and where did you find those terminal blocks? What are they rated for?
Yeah Dave. I share the same concern about the switch soldering itself shut. But hey - lets see what happens.
I was going to make a push-button pre-charge circuit (30-50 ohm 10 W power resistor) but found those antispark plugs that appear to be rated for the job. See them in a vid- OSE 8.0mm ANTI-SPARK CONNECTORS 200 AMP PLUS - YouTube
The power distribution Bus -bar I found at my local electronics shop ($10). It was big enough to accept 8AW wire. A bit of work with the hack-saw and we have those 2 in the picture. I really wanted a pure copper one but that’d require custom machining- so settled on this brass one. Cleaner than making a solder blob, 6 wire connection (I rehearsed several of them). Looks meaty enough to take the current flow. Rating unknown.
Patrick - My thoughts on the raised circles on the terminals.
There just a mechanical tolerance. Instead of having 2 flat surfaces slam down on each-other, there’s more positive contact. Just speculating.
Hope to have some data to share in the coming week. Work really gets in the way of my building time.
