I have (6) 350W motors on the hexa and I was trying to do some battery amp calculations. So 6 x 350W divided by 11.1 = 189A and by this number I"m wondering if my 3S-5000 and 4S-5000 batteries are strong enough for the motors. The 189Amp relates to 31.5Amps per motors. So i think they might be enough but after a 5 or 6 minute flight the battery wires are warm to the touch. But the warmth is extremely small. Anyone have thoughts on this that will make more sense than what I just typed.?
Misc Battery output
- Thread starter WyDiablo
- Start date
RandyDSok
Well-Known Member
To calculate what amperage the batteries can provide... you need to find out what their C rating is...
Divide the MAH rating by 1000 then multiply that by the C rating for the max load the batteries support. On all components ( batteries, connectors, wires, ESC ) always have extra overhead. As mentioned, if the load is 30a... you should use a 40a capable ESC... same holds true on the other components.
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PS... Batteries have two C ratings.. one for the discharge rating and one for the charge rating. In this instance you are interested in the discharge C rating.
Divide the MAH rating by 1000 then multiply that by the C rating for the max load the batteries support. On all components ( batteries, connectors, wires, ESC ) always have extra overhead. As mentioned, if the load is 30a... you should use a 40a capable ESC... same holds true on the other components.
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PS... Batteries have two C ratings.. one for the discharge rating and one for the charge rating. In this instance you are interested in the discharge C rating.
Well, the batteries will supply more than 150A. 30C is the continuous discharge rating, it is not the limit to how much current that will deliver. If you're pulling 189A the batteries will try to supply it. BTW, is that continuous draw or peak capability of the motors?.
Your 3S pack is being worked pretty hard. 189A is about 1.26x the 150A rating of the pack. Maybe not overworked in hovering and slow flight, but aggressive climbs, heavy lifts, and banked turns and whatnot will probably overwork it, which will eventually result in premature failure of the pack.
4S is less current draw load by the motors (140A or so) so you'll be working the batteries in that pack less. I'd run 4S minimum, and might even look into 5S or 6S. 5S current load will be 113A and 6S will be 94A. But 4S gets you below the continuous discharge rating of 30C on a 5000mAh pack. 5S or 6S would allow you to run smaller packs at the same 30C rating, lower C discharge ratings (lower cost), or use the same 5000mAh/30C capacity and get longer flight times.
Your 3S pack is being worked pretty hard. 189A is about 1.26x the 150A rating of the pack. Maybe not overworked in hovering and slow flight, but aggressive climbs, heavy lifts, and banked turns and whatnot will probably overwork it, which will eventually result in premature failure of the pack.
4S is less current draw load by the motors (140A or so) so you'll be working the batteries in that pack less. I'd run 4S minimum, and might even look into 5S or 6S. 5S current load will be 113A and 6S will be 94A. But 4S gets you below the continuous discharge rating of 30C on a 5000mAh pack. 5S or 6S would allow you to run smaller packs at the same 30C rating, lower C discharge ratings (lower cost), or use the same 5000mAh/30C capacity and get longer flight times.
RandyDSok
Well-Known Member
I don't know how you arrive at that conclusion which doesn't match what you said the amperage could be ( possibly )...
You need to find out what the max amps the motor supports or you risk burning it out... then you use an ESC that provides MORE amperage than that so it isn't overworked... then select batteries that can support more amperage than the potential load... and use wiring and connectors that are rated for more than the amperage it needs.
You need to find out what the max amps the motor supports or you risk burning it out... then you use an ESC that provides MORE amperage than that so it isn't overworked... then select batteries that can support more amperage than the potential load... and use wiring and connectors that are rated for more than the amperage it needs.
Lee
Well-Known Member
Are you talking 31A at 100% throttle for those motors?
It seem very unlikely that you will be drawing 31A, unless you punch it at full throttle for a long time, carrying a heavy load.
My QAV weighs 2KG only has 4 motors running 4S and needs 18A ESCs. In a hover it only pulls 5 to 8 amps.
It seem very unlikely that you will be drawing 31A, unless you punch it at full throttle for a long time, carrying a heavy load.
My QAV weighs 2KG only has 4 motors running 4S and needs 18A ESCs. In a hover it only pulls 5 to 8 amps.
No I picked that formula up from another website forum and was really just trying it out on my system to see how mine would compute. But afterwards and then talking to you guys I see that it and myself were way off. I have done some refiguring and I think each motor pulls around 25Amp.
Tony
Staff member
What Lee stated is right. Batteries and ESC's both have a "Burst" rating that is slightly higher than the regular c rating, or amp rating, but is only good for 10 seconds. This is why I suggested putting a watt meter on a motor and seeing what your actual amp draw is. IF it's too high, then you know you will need to go to a larger battery and ESC.
I myself dont' like running things this close as there is always the possibility of burning something up.
As for the question of what ESC is everyone running, I don't have a clue. That would be a Craig question right there. I have never built one of these and in all honesty, never really wanted to other than to have one for the forum.
I myself dont' like running things this close as there is always the possibility of burning something up.
As for the question of what ESC is everyone running, I don't have a clue. That would be a Craig question right there. I have never built one of these and in all honesty, never really wanted to other than to have one for the forum.
Tasajara
Active Member
The thing that gets me is you are figuring on the max the motor is capable of putting out. This does not mean you are going to be at 350 watts when you fly.
My thing is looking at the amps vs voltage and power.
Power = amps x voltage,
Or Power over Voltage X Amps
You have the voltage and you have the power 350 watts(motor Rating) so figure the current by dividing 350watts by the voltage used, 3 or 4s.
That will give you the max amp draw the system would be at given the voltage used, letting you know the size ecs that could be used.
Not what real time amp draw will be in flight.
That given 350 watts divided by 14.8 (4s) will give you 23.6 amps... per motor
350/12.6 (3s) = 27.7 amps per motor
These are max ratings So 30amp esc should be good on 3s or 4s with no problem
If you want more headroom on the esc that is up to you to get a higher rated esc. I use 30 amp on my Hexa with 10x5 props 3s setup. And 9x5 or 10x3.8 if I do 4s.
But in real time flight the amp draw should be no where near the max the system is capable of handling.
As far as the battery if you go 4s with 6 motors 23.6amps per motor will be a max 142amps
3s will be 166.2 amps
So your 3s 5000 30c should put out 150amps cont. as you stated and in real time flight should be fine for the 6 motors.
I fly my Hexa on a 3s 4000mAh 60c but it never gets warm, but I know it is a higher rating. But I have also flown it on a 3000mAh 30c too when testing my gains.
I would bet you are not pulling over 15 amps per motor in normal flight. But this is where an amp/watt meter comes in very handy.
The wires getting warn makes me think of the battery connectors as Tony said.
If you have a bad solder joint or a loose connector your wire will get hot by adding more resistance to the circuit.
It is like have a garden hose with a good flow and then squeezing it and the flow slows.
Current is the same way if you have any point in the circuit that is not making good connection it will increasing amp draw producing more heat.
As in the case of using a real Deans connector vs a copy cat look a like. I tend to use the connectors that are more like bullet connectors.
I use an XT60 on my Hexa with no problem.
Hope this helps, and not just confuse things..
My thing is looking at the amps vs voltage and power.
Power = amps x voltage,
Or Power over Voltage X Amps
You have the voltage and you have the power 350 watts(motor Rating) so figure the current by dividing 350watts by the voltage used, 3 or 4s.
That will give you the max amp draw the system would be at given the voltage used, letting you know the size ecs that could be used.
Not what real time amp draw will be in flight.
That given 350 watts divided by 14.8 (4s) will give you 23.6 amps... per motor
350/12.6 (3s) = 27.7 amps per motor
These are max ratings So 30amp esc should be good on 3s or 4s with no problem
If you want more headroom on the esc that is up to you to get a higher rated esc. I use 30 amp on my Hexa with 10x5 props 3s setup. And 9x5 or 10x3.8 if I do 4s.
But in real time flight the amp draw should be no where near the max the system is capable of handling.
As far as the battery if you go 4s with 6 motors 23.6amps per motor will be a max 142amps
3s will be 166.2 amps
So your 3s 5000 30c should put out 150amps cont. as you stated and in real time flight should be fine for the 6 motors.
I fly my Hexa on a 3s 4000mAh 60c but it never gets warm, but I know it is a higher rating. But I have also flown it on a 3000mAh 30c too when testing my gains.
I would bet you are not pulling over 15 amps per motor in normal flight. But this is where an amp/watt meter comes in very handy.
The wires getting warn makes me think of the battery connectors as Tony said.
If you have a bad solder joint or a loose connector your wire will get hot by adding more resistance to the circuit.
It is like have a garden hose with a good flow and then squeezing it and the flow slows.
Current is the same way if you have any point in the circuit that is not making good connection it will increasing amp draw producing more heat.
As in the case of using a real Deans connector vs a copy cat look a like. I tend to use the connectors that are more like bullet connectors.
I use an XT60 on my Hexa with no problem.
Hope this helps, and not just confuse things..
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Thanks Tasagara that really explains a lot for me. I think I found the problem of the warm battery wire. Like you said above a very very loose wire connection. I use Anderson power poles for connectors. And I think I crimped a 15Amp pole as a 45Amp pole and it wasn't a tight fit for the wire. It pulled completely out of the crimp so now I'm gonna check the other connectors to make sure they are tight. The power poles work really good for me and they are very easy to make the connections. And thanks again for the explaining the electrical part.
