BTW this is the switch being currently being used Amazon.com its nice because of its small size.
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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?
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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.
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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.
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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.
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You are correct to raise the concern. However, I am not going to pretend its outside the capability of anyone. That is a condescending attitude that gets no one anywhere.
You are correct that soldering would not be used in automotive or energy storage. Which is the industry I have worked in for 25 years. It is however almost universally used in “hobby” and consumer electronics packs.
As you probably know, there will almost always be a solderable tab welded to the discharge tabs. They weld “solderable” tabs the the otherwise non solderable tabs for a reason. To make them, well, solderable.
The Bonka packs as used by most here are hobby packs, and built as such. The discharge leads WILL be soldered.
60W is exceedingly adequate for even significantly larger conductors given you have a tip with the thermal capacity. I for one have done it, and with much larger conductors that we are dealing with here.
I must also point out that your comment of 300A through 10awg wire is somewhat incorrect. While 300A through 10awg is excessive, your reasoning was due to fusing. As you must know, the AWG chart specs are based on PVC insulation. Not silicone. The fusing current is far higher with silicone insulation. Which is essentially universally used on hobby packs, and will most certainly be used for the power distribution in this system. You have referenced evidence (the chart) which basically does not apply for anything other than getting the cross sectional area of the conductor of a particular gauge. The fusing specs do not apply.
As these are paramotors, safety and concern is paramount, agreed 100%. However, I have yet to see concern in areas where it would be better placed. Such as interconnects. I have seen some using rather questionable wire terminals for their interconnects. This is of much greater concern IMHO.
There is far greater concern of the house burning down with a loose connection of unknown state in the pack than there would be for him to repair the pack. My extensive experience in the subject suggests to at the very least, open the pack, and ensure the conductor isnt going to short. Leaving it in that state is a much greater fire hazard.
Now you say I am right to raise the concern? But a few posts ago you were saying I was overly concerned? What are we arguing about 
Never said that.
Sorry, I am really questioning your “expertise” now. Fusing is where the wire acts like a FUSE… that means it melts.
Other ampacity charts are rated for when the insulation fails or reaches some high temperature. That occurs at a much lower temperature, and current, than the fusing temperature!
Yes, Silicone insulation can take higher temperatures, but it melts well before copper! That is the point… the insulation will fail at LOWER currents than even the 333A fusing current. I made this clear in my first post.
Further, such fusing current is for the conductor in free air, where it gets cooling. Being in insulation, and even worse in a bundle, only makes it worse.
I am not interested in arguing with you, but please do not criticize me for encouraging people to be cautious.
Yes you are absolutely correct. The danger of wire fusing with PVC insulation VS silicone is far greater. The danger isnt that the wire fuses, its that as fusing takes place, the insulation melts as you have stated, which leads to potential secondary shorting etc. Silicone “melts” at a much higher temperature. It actually doesnt “melt” in the manner plastics do, and as such are safer in over current conditions, or a fuse event. This is precisely the reason silicone insulated wire is used in these sort of applications. I could have been more selective in my wording to convey context better.
The chart assumes wire placement in a wall, with no air flow at 25C ambient, with plastic insulation. Whether you want to conceded to that or not, it clearly states the insulation type is a determining factor in these ratings.
I will point out that silicone is however not nearly as mechanically resilient. It is prone to abrasion and tearing. This is the reason it is not typically used outside of hobby use. So be careful using it around edges of carbon etc.
I didnt criticize expressing caution, I believe I expressed caution as well. Rather the overly cautious approach. Which can lead to dangerous consequences in it own right. Discouraging this guy from repairing his pack could be an example of such.
However, we can both just simply agree that 10awg is a bit on the small side.
Again, the fusing current is when the conductor itself melts. At that point the insulation has already failed. PVC or silicone. Literally at these currents the copper is melting. That won’t change based on the insulation that was once covering it. To imply that the copper in silicone covered wiring will fuse at a different temperature than other insulation is dubious.
Sounds like you are being an alarmist.
I may have missed it, but the chart does not specify the temperature in which copper fuses, only the current at which this temperature is apparently reached for specific gauges, and yes , the insulation, as well as ambient temp, and airflow does plays a role in the rate at which this temperature is reached.
In regard to the second part. Have you ever used silicone wire? Have you ever used silicone wire around relatively sharp abrasive edges? I assure you it DOES fail mechanically.
Is it not a concern to prevent its mechanical failure in the air than the slight risk of exceeding its ampacity for a short period of time in significant airflow? That is not alarmist at all. I didnt start a thread to point out an issue that is just barely an issue. It was an aside , that is just as much of a concern , if not more so in this case.
Even strictly going off the chart , 10ga with a fuse rating of 333A, and a peak of 300A on the paramotor, that gives you an overhead of 11% on ampacity. Which is a bit too close for my comfort personally, but will suffice given the temperature rating of silicone insulation, and the application. With PVC at 300A it will most certainly fail regardless if it fuses or not.
I think you are confusing “ampacity” and fusing. Not the same thing. The insulation is defined for the ampacity rating, which is the current it can carry before the insulation gets to a particular temperature, as defined by the table.
333A is NOT the ampacity of any 10AWG wire! Not anywhere near that. The ampacity will be something much much lower. 300A is way above the ampacity rating.
333A is the fusing current when copper melts. That is independent of the insulation. Those tests are performed on bare wire it appears. I recommend you read the references for the fusing currents.
You want to miles away from the fusing current. 10% isn’t even close. 50% isn’t even good! That was my whole point, which you have missed. If we are this close to the fusing current, we have already grossly exceeded any ampacity rating that any 10 awg silicone covered wiring has.
dude, I was joking with you, relax man.