Pattern only electric powerplant limitations
 

Beginning in January 2022, electric powerplant limitations will allow up to and including 12s packs, 51 volts, for AMA aerobatic pattern competitions.

However, FAI limitations remain at 10s packs, 42.56 volts. FAI competition in the USA is governed by the FAI Sporting Code.This sporting code states:

“Sporting Code 5.1.2.b): Electric powered model aircraft are limited to a maximum of 42.56 volts for the propulsion circuit, measured off load, and prior to flight while the competitor is in the ready box.”


AMA RC Aerobatics Rules state “The AMA Competition Regulations will be applied when the FAI Sporting Code is silent on, or does not provide guidance concerning the conduct or rules of the FAI - F3A events.”. In the case of voltage limitations the Sporting Code has a specific limitation of 42.56 volts.



SO, aside from the FAI, and this questions is for all pattern pilots except the FAI guys


what would be the go to motor and ESC? (if you are considering switching from 10 s to 12 S)

With 3 seasons on my 10S batteries I recently looked at 12S as an option as I needed to buy new batteries anyway. I considered weight, cost and performance. At the end of the day, I stayed with 10S as the only advantage I could see in my case was a slight increase in flight time. Since I will fly either Masters or FAI Silver in 2022, I do not require longer flight time. The cost of batteries were the same and a new motor ( Dualsky 180KV ) and Falcon 21x13 prop would have cost $275 US. I would have used the same OS 1100HV ESC.

I should reword my question.

Lets say I were setting up a brand new pattern airplane. ANd I want to use a 12S system

which motor and esc to use?


(thank you speedrace for reply)

it's not about flight time. It's about efficiency of the equipment. Lower amp draw equates to lower heat in the batteries, motor and ESC. Bottom line the stuff just last longer.

AC and Andrew did a video last week that lays it all out. It's on Facebook.

I would look at Andrew Jesky's new motor wound for 12's. Pretty much any new HV speed controller will handle 12's. Personally, I would consider the Mezon 90 light. Also, Graupner makes a great HV ESC that will work perfect. I'm running one now. As good as Jeti for a lot less dough.

The video did not show any lower heat in the batteries.

The major benefit of a 12's system is longer battery life due to lower heat. Heat kills batteries. "High current draw...high heat...low life. Low current draw....low heat....longer life.".

This is more less nonsense, at least for batteries.
Of course if you only reduce current draw and keep the battery same that would apply.

Here it is the question of 10S vs. 12S heat generation when everything else is kept equal. That means battery energy capacity, size/weight, cell quality & grade, and battery age/condition. Good examples would be 10S 6000mAh vs 12S 5000mAh or 10S 5000 mAh vs. 12S 4200mAh. Those pairs have equal amount of energy capacity.
Now, compared to 10S equivalent the 12S cell capacity in the battery is smaller (by 1/6 or 17%) and hence has a bigger internal resistance (again in the same proportion). This results the stress on the cell is on the same level in both, 10S and 12S, batteries. The heat generation is the same for both. Please measure this and show evidence if you do not agree.

If you do not keep the weight and energy capacity same for 10S vs. 12S comparison then it is all useless. In a similar way I could say that 10S is better because I can use 10000mAh batteries and they do not get as warm as your packs. Not useful, right?

Truth is and is based on laws of physics, that to use 12S instead of 10S would call for change in motor/prop combination and battery configuration. These changes will counter the benefits that reduced current draw would bring. The ESC will benefit from reducing current draw and there you could go to one side smaller one in some cases.

You can also gain more efficiency by rewinding a motor to have more copper area in the winding. This will reduce internal resistance and improve efficiency with less heat. So, be careful, when you compare different combinations. It is not always clear which change causes the biggest benefits.

It always boils down to heat in lipo longevity. Andrew didn't need to say anything about heat, it's a given. When I said "lower current draw equates to lower heat", I should have explained a bit further. I will give you that the heat build up may or may not be attributed to current draw during the flight (although I still do believe there will be less heat buildup during the flight with 12's, but I'm not going there).

The real issue is "how hard are you pushing your packs"? We can all agree that if you are landing with 10% capacity remaining in a battery it's going to suffer more than a battery with 40% capacity left. Again it's all about heat buildup in the battery. In the battery we pushed hard, heat has increased, which raises the internal resistance of the cells. The next time we fly it, due to high internal resistance, more heat is generated which further harms the pack by raising the internal resistance even more....on and on.

When AC and Andrew say they are killing packs in one flight at the NATS and Worlds, again it all comes down to heat that ultimately killed the pack. Due to having a more efficient system with 12's, they can fly an eight minute unknown and land with a reasonable reserve in their batteries and not harm them (hopefully).

So yes, a 12's system may give longer flight times (based on battery selection), but again, that's not the issue for most of us. For the few guys that fly eight minute Unknowns at the NATS and Worlds, yes a 12's system may give them longer flight times, but for us mortals, that don't need longer flight times, the advantage of 12's is longer battery life (due to less heat).

You are mixing things.
Yest,it is given that that heat will kill the packs.
But, you may be astonished finding out that if you draw 80% of packs energy and max current is 40% of packs maximum, heat generation is the same, regardless if they are 12S or 10S.

In Andrew's and AC's video they did not show, nor anyone else has shown, any proof or theoretical base to support 12S packs to produce less heat over 10S.

No, you don't get it....

If I land with a pack that has 5% capacity left, I have toasted the pack due to heat......period.

If I land with 50% left, the pack has not been pushed hard and will not suffer from heat (thus the internal resistance has not increased). The big heat buildup is at the end, when you push a pack to close to depletion......period.

I'm done....gone luck with your packs that you push to 5%

Well,
in the proofing video both 12S and 10S packs used same amount of energy. In mAh the 12S one used 1/6 less but the cell is also 1/6 smaller (providing the packs were equal in weight).
So, packs used same percentage of their capacity.

But, suit yourself. Try 12S yourself and be happy.

I'm no expert but isn't the difference in remaining capacity more of a function of capacity than voltage?

IF that is the case would it make more sense to fly 10S 6000 vs. 12S 5000? I get that if the voltage is higher the throttle is lower and consumption will be lower but you could accomplish the same thing using a higher capacity pack. if you use 4000mah a flight that is 80% of a 5000 pack or that same 4000mah is roughly 67% of a 6000 pack leaving more safety capacity and less heat.

I am asking for my own edification not pretending to understand or pick a side.

The I^2*R part gets you with the batteries. Half the current at twice the resistance is half the power loss. For the sake of simplicity this completely ignores any local spot heating that may occur.

In a perfect world, with a motor rewound for half the current you'd get 4 times the resistance, so the I^2*R losses would be the same.

I agree when comparing apples with apples that there's not a massive efficiency gain on paper going from 10S to 12S. From a flight performance perspective though a few extra watts on tap when you need it can certainly improve the overall efficiency of the flight reducing the total amount of energy needed.

I can only guess that they've introduced this in the US so somebody can put an equivalent power 12S system into an airframe using cheaper parts?