Help! When I run dual ESC should I run 2 batteries or 1
- Thread starter tuckerlm
- Start date
Foamforce
Elite member
Merv, correct me if I’m wrong here.
If you run one battery per motor, one battery can die before the other and cause asymmetric thrust (plane spins around). The upside is that less amperage flows through the wires, which could be an advantage if you’re running close to the limits.
If you wire both batteries in parallel using a Y connector, and then split that back out with another Y connector to connect each ESC, then the batteries will drain more evenly, preventing asynchronous thrust. However, you might be running a lot of amps through that central connector. I’ve had some pretty warm wires from this, but not bad. Also, I think running the batteries in parallel keep the voltage from the two batteries even, so that one wouldn’t become much more discharged than the other.
Merv, does that sound right?
Yes, sounds like a good idea.
I would use 2 batteries that are the same size & similar age. This will minimize any difference between them.
Shurik-1960
Well-known member
The number of batteries depends on the position of the CG and the flight weight of the model, determined by the total thrust of the engine. The battery parameter C depends on the power consumption. You can put 10 batteries and the model will turn into a brick.The total thrust of the power plants makes it possible to determine the maximum flight weight of the model. Subtract the weight of the empty model from this weight to get the maximum weight of the batteries. Next, we select the batteries based on the weight and power output.
L Edge
Master member
What model are you building?
This may determine if you use 1 or 2 batteries. The limit may be the location of the battery in the fuse to get the CG right. It may not be (long enough or high enough to insert 2 batteries
When I built my A-10, Edf's were far enough forward and fuse wide enough that I could use 2 batteries. My DarkStar Edf's were all the way back that the NYGAD fuse(skinny and low and getting CG right) allowed only one battery.
When I design with 2 EDF's, I always use one battery so I don't have to worry about bad yaw problems(yes, I have had that in flight when I designed a J-20 Chinese plane using 2 battery's).
EDF transports are real easy and can handle either real well. Did one where EDF's were on top of wing and explored blown flaps that worked.
This may determine if you use 1 or 2 batteries. The limit may be the location of the battery in the fuse to get the CG right. It may not be (long enough or high enough to insert 2 batteries
When I built my A-10, Edf's were far enough forward and fuse wide enough that I could use 2 batteries. My DarkStar Edf's were all the way back that the NYGAD fuse(skinny and low and getting CG right) allowed only one battery.
When I design with 2 EDF's, I always use one battery so I don't have to worry about bad yaw problems(yes, I have had that in flight when I designed a J-20 Chinese plane using 2 battery's).
EDF transports are real easy and can handle either real well. Did one where EDF's were on top of wing and explored blown flaps that worked.
I am doing a scratch build of my own design with plenty of room for 2 batteries, but I think I will stick to one. I was trying to figure out what mah batterie to run. I plan on using dual 70mm 12 leaf 4s 2600kv EDFs with an amp draw of 62 and 992 watts at full throttle. any idea how to calculate this? I am currently looking at a 6300mah 60c battery is this to big?
Last edited:
L Edge
Master member
What are the dimensions of the plane(pic would also help) and what approximate weight will it be fully ready to fly?
Do you have landing gear?
quorneng
Master member
You need to consider how long you want to be able to fly.
At full power of 124A a 6300mAh battery would last 6.3/124 x60 = 3.04 minutes. That rate is equivalent to a 20c discharge rate. On this basis your 6300mAh 60c battery should manage ok.
Of course if you use some throttle management you will be able to fly for a bit longer.
At full power of 124A a 6300mAh battery would last 6.3/124 x60 = 3.04 minutes. That rate is equivalent to a 20c discharge rate. On this basis your 6300mAh 60c battery should manage ok.
Of course if you use some throttle management you will be able to fly for a bit longer.
L Edge
Master member
If it weighs 6 lbs, no problem. Most 2 70mm edfs usually weigh 8-9 lbs.
quorneng
Master member
tuckerlm
My recommendation for a first design is don't be shy on the tail moment. Both in pitch and yaw. Your V tail not only looks to be pretty modest but is also on quite a short rear fuselage.
In general small tail surfaces on a long moment arm are easier to manage than big surfaces on a short moment.
Given the velocity of the air exiting an EDF make sure the tail surfaces are well clear of the exhaust efflux. A T tail might be better than a V.
The fuselage of your design looks pretty bulky. Does it hold any particular significance? An EDF actually likes to go fast so aerodynamic drag is best kept to as low as possible.
Finally an EDF is all about the ducting, particularly the inlet. Any losses due to inlet restrictions mean the fan has to do work to simply restore the natural inlet air velocity from the plane flying before it can generate any thrust by raising the air velocity further.
Not for nothing do most EDF manufacturers quote their EDF "static" thrust figures when operating stand alone in "free air" with no ducting other than the bell mouth and the duct from the EDF body.
I look forward to your design as it progresses.
My recommendation for a first design is don't be shy on the tail moment. Both in pitch and yaw. Your V tail not only looks to be pretty modest but is also on quite a short rear fuselage.
In general small tail surfaces on a long moment arm are easier to manage than big surfaces on a short moment.
Given the velocity of the air exiting an EDF make sure the tail surfaces are well clear of the exhaust efflux. A T tail might be better than a V.
The fuselage of your design looks pretty bulky. Does it hold any particular significance? An EDF actually likes to go fast so aerodynamic drag is best kept to as low as possible.
Finally an EDF is all about the ducting, particularly the inlet. Any losses due to inlet restrictions mean the fan has to do work to simply restore the natural inlet air velocity from the plane flying before it can generate any thrust by raising the air velocity further.
Not for nothing do most EDF manufacturers quote their EDF "static" thrust figures when operating stand alone in "free air" with no ducting other than the bell mouth and the duct from the EDF body.
I look forward to your design as it progresses.
Thank you for the feedback I will definitely change the tail out. The reason for the bulky fuselage is it's supposed to be a payload carrier but I will try to streamline it a bit more. I can widen the inlet to the EDF, and the exhaust is currently 85% of the fan size. because I saw somewhere that the exhausts should be a little smaller than the fan.
quorneng
Master member
tuckerlm
That is a definite improvement although the inefficiency of EDFs (about half that of a prop) does not make them ideal for load carrying applications. The size of battery needed tends to be the load.
You are correct about the using a reducing "nozzle" of about 85% of the Fan Swept Area (FSA). Note this is the area of the fan and does not include the area of the fan hub/motor. Such a nozzle optimises the exhaust velocity but if your plane is a slower flyer there can be advantage in leaving the exhaust at the FSA to gain maximum static thrust. Optimising EDF ducting does require a bit of mathematics!
A rather stylized EDF in a duct with a thrust tube reducing to 85% FSA.
With an inlet duct the EDF itself does not use a bell mouth. However for maximum static thrust the actual inlet mouth should be radiused to maximise inlet flow.
It is worth noting that the most efficient EDF has the very minimum of ducting which is exactly why modern airliners stick their turbo fans on the "outside" rather than buried within the structure, however supersonic jets do not do this as the shock waves from such an externally mounted arrangement would be structurally dangerous.
I hope this helps.
That is a definite improvement although the inefficiency of EDFs (about half that of a prop) does not make them ideal for load carrying applications. The size of battery needed tends to be the load.
You are correct about the using a reducing "nozzle" of about 85% of the Fan Swept Area (FSA). Note this is the area of the fan and does not include the area of the fan hub/motor. Such a nozzle optimises the exhaust velocity but if your plane is a slower flyer there can be advantage in leaving the exhaust at the FSA to gain maximum static thrust. Optimising EDF ducting does require a bit of mathematics!
A rather stylized EDF in a duct with a thrust tube reducing to 85% FSA.
With an inlet duct the EDF itself does not use a bell mouth. However for maximum static thrust the actual inlet mouth should be radiused to maximise inlet flow.
It is worth noting that the most efficient EDF has the very minimum of ducting which is exactly why modern airliners stick their turbo fans on the "outside" rather than buried within the structure, however supersonic jets do not do this as the shock waves from such an externally mounted arrangement would be structurally dangerous.
I hope this helps.
Similar threads
