A slipping prop = no load on the motor, or less load in this case. Current drops as that is a function of torque. Stator losses are a function of current, not speed.
Just saying that an unloaded motor does not cause the over heat event. Rather, the opposite is true; overloading the motor increases current.
Unless it got hot from friction at the prop…
Makes sense to put a secondary lock on those props! Wiring temps look good, which prop type are you using, the 22x10 or 22x14?
I’m using the 22x10’s. Yeah, the wiring temps and batteries looked good - I drained about 25% of the battery in the test. Looks promising for full battery load test.
Yeah, I’d really like some secondary sort of lock, but not sure what that would be. Anyone have ideas?
did this happen to all four props or just one, and is it as you say something to do with the locking rotation?
Just one of them. A second one had a separate issue with a wobbly prop shaft, which lead to that motor getting considerably hotter than the others 2
BTW this is the switch being currently being used Amazon.com its nice because of its small size.
Any chance of having a short (Woodruff) keyway scallop cut into the CCW motor shafts where they pass through the props? Parallel cut inside the prop also. Some motor suppliers offer a keyway cutting service, although these tend to be on parallel shafts ( is that one tapered?)
Thanks Paul!
BTW, Talking about the potential of loosening props, can your motor supplier provide prop mounts with left-handed threads (and nuts) to help mitigate the concern?
How about some Locktite on those nuts, instead of using the nylon version?
Would castle nuts and pins be an option?
Ya I had to get the motor standoffs custom cut for the spacing I needed so I can make any changes we want. I do already have ccw and cw threaded shafts but from the testing I’ve done I thought it wouldn’t be necessary and would make the kits more confusing to build. We can always go back the ccw and cw threaded and nuts if we need to.
@Pdwhite, do you have a response back from Bonka yet about the 10 AWG wires included in our group buy? Just wondering if they offered a remedy to the problem. I did peek through where the wires come out and I think they might actually be soldered. That would make them easier to fix but it would mess up the packaging to do “LiPo Surgery” and many people on the forum have strongly cautioned against that.
They are most certainly soldered to the discharge tabs.
There is nothing wrong with tearing into the pack end to do a repair if you need to.
Your not doing anything drastic removing the very basic layer of protection to do a repair. Just watch out with metal objects as to not create a short.
In fact if you have a loose connection under the “hood” of your pack, you are better off opening it up and fixing the issue, or at the very least pulling out the loose wire as to prevent it shorting.
Just make sure if you do this, to re-insulate it properly and close it up as it was.
There is little difference in opening the pack as there is to having the discharge leads bare when soldering connectors etc. The lack of understanding of what is under the hoof there and why people “strongly” caution against it is silly. Yet they are OK with you doing the wiring external to the pack, or even building your own pack. Makes very little sense.
The terminals are indeed closer together, and can be shorted more easily if not careful, and there is certainly risk , but no more than any other part of the electrical system on this thing.
It is more unsafe to have a loose connection in the pack. Open it up and fix it.
I haven’t seen much talk about using 14 cells. The speed controllers and the throttle controller support that. Do the motors support that? I know more volts requires fewer amps to get the same watts so wouldn’t that be better or would the drop in amps not be significant enough? Are 7 cell batteries readily available?
I assume we would have to use smaller props because higher volts would produce higher RPMs and that would be aerodynamically less efficient. But in return we would use fewer amps for the same output watts which is better on the batteries and wires.
Yes the whole system supports 14 cell (60v)
Actually the ESCs and Motors do but the BEC voltage step-down only supports 50 currently
That’s good to know but would we need different props to make that change?
I assume you are talking about my cautionary statements. I am afraid that maybe you don’t understand the issue here.
Soldering directly to the cell tabs is dangerous because you are heating up the cell directly. The size of the cell, and the big conductors of such a cell make it difficult to solder to if you don’t have an iron powerful enough.
The cell will wick away heat from the joint. A small iron will struggle to get the joint hot enough all the while the cell is heating up. The weaker the iron, the longer it is held to the cell terminal, the more heat transfer. Solder flows at over 200C! Thermal runaway occurs around 150C.
You want a big iron that can heat it up quickly and be done. It is not trivial and is beyond the capability of many. It cannot be compared to soldering wires and conectors.
So yes, the caution is valid.
That is true, and I am glad you brought that up as the point as to why you express caution.
Your statement of it being beyond the capability of most is not true. A typical 60W iron, with an adequately sized tip is exceedingly adequate for these size tabs.
If the equipment these people have are capable of soldering the heavy gauge wire used in the system, then it is adequate to solder the tabs.
That is not accounting technique, which can have a significant impact.
Dont be such an alarmist. Most of these people building these things have a bit of a head on their shoulders. If you feel they cannot safely solder to a cell tab, a more accurate statement on your part would be to tell them to drop the project entirely as they wouldnt be capable of doing the rest of it.
I have assembled thousands of packs with varying methods for industry. Soldering prismatic pouch cell tabs being a major part of that. I assure you it isnt nearly worthy of such an alarmist position as you take.
I did quote “strongly” suggesting the strong alarmist position is a bit excessive, however there is certainly some caution to be taken.
Dude, giving people advice in hopes they don’t burn down their home or hurt themselves is not being an “alarmist”. It is just real advice to a real concern.
I doubt anyone here has experience solding to 22 amp hour cells. I don’t, but i can tell you It is no joke and shouldn’t be taken lightly. I would not attempt with a 60W iron. Probably 100W… Getting away with it is not evidence it is safe.
I work in the “industry” too, for what that is worth. As you may know, no real industry like automotive or grid storage would solder to a cell… Spot welding is used for this very purpose; to avoid heating up the cell. I have been witness to a thermal runaway event, all caution should be taken to avoid.
Lots of smart people here, but many may not understand these things. Evidenced by the fact that me, a casual observer that doesn’t own an OpenPPG, had to raise the issue of drawing 300+ amps from 10 awg wire.
As paramotor pilots, safety should be at the fronts of everyone’s mind. That extends to building phase. No alarms, just education.
