100 KV U10 Motors on 12S and 28X9.2" props ... not efficient !!!??
- Thread starter khaled_abobakr
- Start date
FerdinandK
Member
... if your copter layout meets the requirements ...
If you can fly with standard packs more that 12-15min, it is of advantage to use that high density (>180Wh/kg) packs, if your copter does not reach 12-15min with standard packs, they will not work (you have to change something else first e.g. reduce weight, increase battery mass, become more efficient, ...)
best regards
Ferdinand
If you can fly with standard packs more that 12-15min, it is of advantage to use that high density (>180Wh/kg) packs, if your copter does not reach 12-15min with standard packs, they will not work (you have to change something else first e.g. reduce weight, increase battery mass, become more efficient, ...)
best regards
Ferdinand
Just made this out for the Tattu 6S range..
Capacity/C rating/Wh/Cost/Cost/Wh
10000 mAh 25C = 153.95 - 200 Euro 77cents/Wh
16000 mAh 15C = 184.85 - 280 Euro 66cents
4500 mAh 25C = 140.1 - 85 Euro 1.64 Euro
22000 MaH 25C = 194.66 - 480 Euro 40cents
9000 mAh 25C = 170.33 - 180 Euro 94 cents
12000 mAh 15C = 168.93 - 210 Euro 80 cents
7000 mAh 25C = 171.24 - 142.50 Euro 1.20 Euro
10000 mAh 15C = 170.77- 172 Euro 99cents
A comparison to the battery that is currently my favourite..
Desire 6S 35C 8300 mAh..
8300 mAh 35C = 165.26 £145 £1.13/Wh (1.41 Euros) ... hmm!
For the record just also adding weight and dimensions if you want it for the spreadsheet..
1442g 165* 65.12 *62.18mm
1932g 180*74*65 mm
713g 138*44* 56mm (L * W * H)
2509g 195*91*64mm
1173g 208*73*37mm
1577g 181*70*62 mm
907.5g 136.48*42.07*68.28 mm
1300g 165* 65.12 *62.18mm
Capacity/C rating/Wh/Cost/Cost/Wh
10000 mAh 25C = 153.95 - 200 Euro 77cents/Wh
16000 mAh 15C = 184.85 - 280 Euro 66cents
4500 mAh 25C = 140.1 - 85 Euro 1.64 Euro
22000 MaH 25C = 194.66 - 480 Euro 40cents
9000 mAh 25C = 170.33 - 180 Euro 94 cents
12000 mAh 15C = 168.93 - 210 Euro 80 cents
7000 mAh 25C = 171.24 - 142.50 Euro 1.20 Euro
10000 mAh 15C = 170.77- 172 Euro 99cents
A comparison to the battery that is currently my favourite..
Desire 6S 35C 8300 mAh..
8300 mAh 35C = 165.26 £145 £1.13/Wh (1.41 Euros) ... hmm!
For the record just also adding weight and dimensions if you want it for the spreadsheet..
1442g 165* 65.12 *62.18mm
1932g 180*74*65 mm
713g 138*44* 56mm (L * W * H)
2509g 195*91*64mm
1173g 208*73*37mm
1577g 181*70*62 mm
907.5g 136.48*42.07*68.28 mm
1300g 165* 65.12 *62.18mm
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R_Lefebvre
Arducopter Developer
Hi Ferdinand,
I've just added your battery to my spreadsheet. I also added another column with the inverse calculation for density. Though I think one of these should actually be called specific energy, I'm not sure which! Semantics...
Looks like the advertised specs of the Hobby King Multistar batteries are similar to those of the Tattu. So far I'm a big fan of these batteries. I have not actually tested the manufacturer claims yet. I flew two nights ago for 25 minutes, but got bored and landed. Still had 3.8V/cell. I'll see how much capacity goes back in. Eventually I'll just grab a lawn chair and a beer, put it in Loiter and see what happens.
That's an interesting concept you have about being able to use 100% of the battery, if you are discharging it slowly. I was thinking it was odd that we rate batteries according to mAH, but can only ever use 80%, it would seem that the ratings should be lower.
One thing I'll say though, is that when pushing the lower limits of voltage in flight, it becomes more important to monitor the individual cell voltage. When I have done this, I usually find one cell dumps before the others (goes below 3.0V, while others at 3.3V) and this further damages the cell. This might be only a problem with Hobby King batteries though.
I also agree, that the high-C ratings are just garbage. No way that battery can deliver that power. IMO, it's just false advertising by the manufacturers who greatly mark up the price of the battery. Somebody else got caught with this... who was it? They were labelling them 60C or something, and somebody pushed them hard and they failed. The company ended up admitting that the cells were only really 5C, and the 60C was a 1 second burst rating. So they went completely against the standard labelling convention where the C rating is supposed to be the continuous discharge rating.
If somebody wants to test out one of those 120C batteries, just send me one, I can hook it up to the winch on my Land Rover and see what happens. It's interesting because the winch actually can pull up to a 1000A in full stall, but it uses 2AWG wiring, IIRC. Would be fun trying to run 1200A through 10AWG.
I've just added your battery to my spreadsheet. I also added another column with the inverse calculation for density. Though I think one of these should actually be called specific energy, I'm not sure which! Semantics...
Looks like the advertised specs of the Hobby King Multistar batteries are similar to those of the Tattu. So far I'm a big fan of these batteries. I have not actually tested the manufacturer claims yet. I flew two nights ago for 25 minutes, but got bored and landed. Still had 3.8V/cell. I'll see how much capacity goes back in. Eventually I'll just grab a lawn chair and a beer, put it in Loiter and see what happens.
That's an interesting concept you have about being able to use 100% of the battery, if you are discharging it slowly. I was thinking it was odd that we rate batteries according to mAH, but can only ever use 80%, it would seem that the ratings should be lower.
One thing I'll say though, is that when pushing the lower limits of voltage in flight, it becomes more important to monitor the individual cell voltage. When I have done this, I usually find one cell dumps before the others (goes below 3.0V, while others at 3.3V) and this further damages the cell. This might be only a problem with Hobby King batteries though.
I also agree, that the high-C ratings are just garbage. No way that battery can deliver that power. IMO, it's just false advertising by the manufacturers who greatly mark up the price of the battery. Somebody else got caught with this... who was it? They were labelling them 60C or something, and somebody pushed them hard and they failed. The company ended up admitting that the cells were only really 5C, and the 60C was a 1 second burst rating. So they went completely against the standard labelling convention where the C rating is supposed to be the continuous discharge rating.
If somebody wants to test out one of those 120C batteries, just send me one, I can hook it up to the winch on my Land Rover and see what happens.
It's interesting because the winch actually can pull up to a 1000A in full stall, but it uses 2AWG wiring, IIRC. Would be fun trying to run 1200A through 10AWG.
FerdinandK
Member
Of course it is important to monitor every cell, Jeti has even voltage sensors you can plug in the balancer wire of the pack. But if you "know" your batteries you can also see the first cell dropping, since this is the first rapid (within seconds) voltage drop you can see.
best regards
Ferdinand
best regards
Ferdinand
R_Lefebvre
Arducopter Developer
Yes, but in my experience, it's usually too late. On these bad packs, if I wait until I can see the voltage drop quickly, by the time I actually get it on the ground it's too late, and that cell is usually under 3.0V already. It can happen very fast.
I suppose if you're just sitting there over the landing pad in position hold, watching the voltage reading intently.... But if I'm actually flying, I can't devote that much attention to it.
I suppose if you're just sitting there over the landing pad in position hold, watching the voltage reading intently.... But if I'm actually flying, I can't devote that much attention to it.
FerdinandK
Member
R_Lefebvre
Arducopter Developer
I'm not sure if you're being sarcastic or not.
I'm typically flying around at up to 150 km/h. Or doing Acro. It's pretty rare that I'm sitting over a landing area.
I'm typically flying around at up to 150 km/h. Or doing Acro. It's pretty rare that I'm sitting over a landing area.
+1 on monitoring individual cells, I have yet to see an instance where one or two cells do not discharge faster than the others towards the end, even on perfectly balanced or new packs. The FrSky smarport voltage sensor used with Taranis works great for that as you can set an alarm for the lowest cell ...
That said and as Ferdinand says, you can usually see it coming as the total voltage simultanously skydives right when the lowest cell(s) go down. One thing that has worked for me through experimentation when I really want to push things is to set an alarm on the lowest cell at a voltage that gives me 30 seconds to land. That point can usually be determined reasonably accurately after a few flights "over the landing pad in position hold"
That said and as Ferdinand says, you can usually see it coming as the total voltage simultanously skydives right when the lowest cell(s) go down. One thing that has worked for me through experimentation when I really want to push things is to set an alarm on the lowest cell at a voltage that gives me 30 seconds to land. That point can usually be determined reasonably accurately after a few flights "over the landing pad in position hold"
R_Lefebvre
Arducopter Developer
Is it consistent across packs though? Or do you have to change the setting with each pack you load?
I guess my point is this: While it may be true that it is technically possible to use 100% of the pack, safely, it does require quite a bit of extra effort. In operation, landing at ~80% just makes things easier, so you can concentrate on what's really important. Because landing at 98% of the packs capacity is fine. But landing at 102% of the pack's capacity is very bad.
However, if you're trying to set an endurance record, then have at it.
I guess my point is this: While it may be true that it is technically possible to use 100% of the pack, safely, it does require quite a bit of extra effort. In operation, landing at ~80% just makes things easier, so you can concentrate on what's really important. Because landing at 98% of the packs capacity is fine. But landing at 102% of the pack's capacity is very bad.
However, if you're trying to set an endurance record, then have at it.
khaled_abobakr
Member
Hi
I'm really learning new things from all the replies in here ... Thanks a lot to you all gentlemen
Okay
I flew today for 5 mins ... and put back 2400 mAh back to the 12S 10,000 mah Gens Ace lipo pack
I was just hovering about 1 meter from the ground so I can see the watt meter ...
I was pulling 24 amps , 1200W during the hovering ... and it took off at 1/4 or 1/3 throttle stick...
So I assume I can hover like this for 16 mins and use 80% of the pack (standard high discharge lipo) 8000 mAh
Thanks
Khaled
I'm really learning new things from all the replies in here ... Thanks a lot to you all gentlemen
Okay
I flew today for 5 mins ... and put back 2400 mAh back to the 12S 10,000 mah Gens Ace lipo pack
I was just hovering about 1 meter from the ground so I can see the watt meter ...
I was pulling 24 amps , 1200W during the hovering ... and it took off at 1/4 or 1/3 throttle stick...
So I assume I can hover like this for 16 mins and use 80% of the pack (standard high discharge lipo) 8000 mAh
Thanks
Khaled
Last edited by a moderator:
R_Lefebvre
Arducopter Developer
Yeah, eCalc shows you were not operating in an efficient range for those motors. It'll be more efficient on 8S. Like 50% efficiency vs. 80% efficiency.
Is this your desired AUW? If it is, then you need to reduce system voltage, use lower pitch props, or use lower kV motors.
Is this your desired AUW? If it is, then you need to reduce system voltage, use lower pitch props, or use lower kV motors.
If you can get 16 minutes on one pack that’s starting to look nice ..
At 3.2kg a 10AH pack you are nowhere near the optimal battery weight for long flight times given your set-up: Looking at the t-motor data for the u10 and 29” props, you should roughly get 6kg of thrust at 75% and 9kg at 100% per motor, so 24kg total at 75% and 36kg at 100%, on 12S.
Seems therefore that a 20kg AUW, give or a take a couple, would be quite reasonable depending on your application and maneuverability confort level (unless you want to break records and in that case you can/should go higher). Given your “empty” frame is at 7.5kg, you have plenty of room to load up ...
So my guess would be that if you triple your battery load to 30AH and 9.6 kg, or a bit more (say 35ah) you might get 30+ minutes of flight time or who knows, beyond, and still have room for a 3-4kg payload. Or better yet get 30-40AH worth of 8S, you may not end up lifting as much but depending on your final application that may work out and you’ll get even longer flight times.
Nice heavy lifter ... Would really be interested in what you end up going for and the kind of flight times you’ll get. Is this for a 5Dm3 or equivalent, Red Epic , or some other application?
At 3.2kg a 10AH pack you are nowhere near the optimal battery weight for long flight times given your set-up: Looking at the t-motor data for the u10 and 29” props, you should roughly get 6kg of thrust at 75% and 9kg at 100% per motor, so 24kg total at 75% and 36kg at 100%, on 12S.
Seems therefore that a 20kg AUW, give or a take a couple, would be quite reasonable depending on your application and maneuverability confort level (unless you want to break records and in that case you can/should go higher). Given your “empty” frame is at 7.5kg, you have plenty of room to load up ...
So my guess would be that if you triple your battery load to 30AH and 9.6 kg, or a bit more (say 35ah) you might get 30+ minutes of flight time or who knows, beyond, and still have room for a 3-4kg payload. Or better yet get 30-40AH worth of 8S, you may not end up lifting as much but depending on your final application that may work out and you’ll get even longer flight times.
Nice heavy lifter ... Would really be interested in what you end up going for and the kind of flight times you’ll get. Is this for a 5Dm3 or equivalent, Red Epic , or some other application?
Not quite consistent, but good enough when I like to operate between 80-90% discharge for those extra (few, 1-2 minutes) ... Rare but it's been useful if not required a few times. (I never go to 100% unless as an experiment to get a feel for that steep discharge curve end).
Not into setting records , I live at 1,600 meters so right of the bat I don't stand a chance against the likes of Ferdinand!
Besides I use mundane batteries (Mostly Turnigy yellow compacts). The new green multistars are really appealling though, these are on my list.I do like to push things once in a while, though, especially on those rigs where I went with more expensive larger props ... want to get my money's worth in flight time's ...
khaled_abobakr
Member
I hovered for 7 mins with 10 Kg payload at 2700W / 60A with 10,000 mah 12S
Sounds about right with 10,000 mah. Maybe you could have pushed it to 8 minutes? (or about 80% capacity at 60A) So if you converted this 10kg payload in batteries (3 at 3.2kg each) you'd get 8x4 = 32 minutes and a bit more flight time ... Or 24 minutes with 3.6kg payload, weight in the range of a 3axis BL gimbal loaded with a 5d. Sure beats a lot of heavy lifters ...
FerdinandK
Member
@khaled_abokakr
10kg payload for 7min is not bad. Did you measure the motor temps after flight? I still think that with lover voltage you could get some extra minutes. From my point of view a proper setup for 10kg payload would need 10kg battery too.
@R_Lefebvre
If you set a voltage alarm that is sufficient (all you have to do is to wait for the --beep-- beep-- beep). Capacity used is a result (a-posteriori) from a given (a-priori) strategy to stop after some time, or at a predefined voltage. So if you use 80 or 102% of your capa is not the criteria it is the result. Also 102% even 110% capa used will never damage your cells, it is the low (or too low) voltage under load that does the job.
If you just sit and wait in front of you hovering copter, and stop at a predefined voltage, you possibly get 102% capa.
If you really fly (150km/h) and do aerobatics, and stop at the same predefined voltage, you possibly get 80% of the capa only.
... and there is a difference between irony and sarcasm.
best regards
Ferdinand
(sitting and waiting in front of my hovering copter - others would call that meditation and waiting for <dfn title="Religion / Religion" style="word-wrap:normal;;float:right">relig </dfn>enlightenment)
10kg payload for 7min is not bad. Did you measure the motor temps after flight? I still think that with lover voltage you could get some extra minutes. From my point of view a proper setup for 10kg payload would need 10kg battery too.
@R_Lefebvre
If you set a voltage alarm that is sufficient (all you have to do is to wait for the --beep-- beep-- beep). Capacity used is a result (a-posteriori) from a given (a-priori) strategy to stop after some time, or at a predefined voltage. So if you use 80 or 102% of your capa is not the criteria it is the result. Also 102% even 110% capa used will never damage your cells, it is the low (or too low) voltage under load that does the job.
If you just sit and wait in front of you hovering copter, and stop at a predefined voltage, you possibly get 102% capa.
If you really fly (150km/h) and do aerobatics, and stop at the same predefined voltage, you possibly get 80% of the capa only.
... and there is a difference between irony and sarcasm.
best regards
Ferdinand
(sitting and waiting in front of my hovering copter - others would call that meditation and waiting for <dfn title="Religion / Religion" style="word-wrap:normal;;float:right">relig </dfn>enlightenment)
khaled_abobakr
Member
Hi
Motor temps were just warm ..
Thanks
Khaled
Motor temps were just warm ..
Thanks
Khaled
khaled_abobakr
Member
I like that ... and I enjoyed hovering that roaring beast , it flew with 10 kg payload as if it was not carrying anything at all ..
According to Tiger motor specs of the U10 . on octo , 12S, 28" props .. AUW is 36 KG ... and this is only 4.5Kg of thrust per motor , while max thrust is 8.1 KG per motor ...
