I'm trying to size the LiPo pack for a 3DR Hex by using the xcopterCalc calculator at
http://www.ecalc.ch/xcoptercalc_e.htm
and RCTimer motor details for the 880kv with 40cm cable at
http://www.rctimer.com/index.php?gOo=goods_details.dwt&goodsid=...
Using the xcoptercalc with 11x4.7 prop & 4S battery I'm getting 3 red flags.
- Motor max watts are exceeded
- battery current max amps are exceeded
- Motor max temperature of 100 C exceeded
- (see attached)
So my questions are:
- Is this interpretation (a,b,c above) of the calculator's results correct?
- Are these 3 red flags serious enough to avoid a 4S LiPo and use a 3S?
- Xcoptercalc calculated no issues with a 3S. (see attached)
- Is xcoptercal the best method to determine battery cells for a Hex?
Depending on what I learn from the above questions,I'll likely choose:
4S 6000mah 60c 120c max LIPO for 11x4.7 prop or....
3S 6000mah 40c 100c max LIPO for 10x4.7 prop
Thanks in advance for your insights & comments!
Replies
Which APM are u running? I run one of those $5 buzzers on each pack, but I doubt Id be able to hear it so I bring my quad down after 15 minutes (or less)
But in my MP I have a readout for bat voltage in the bottom left of the HUD. Isn't that a readout for the plane/copter's battery voltage?
Hi Stephen,
I am also building my first Hex. But I have built a quad and a Y6. On my Quad with 880KV motors and 12x3.8SF Props and the whole thing weighing 2.3kgs with a Zippy 8000mah lipo 3s , I get 14mins flight time. But after reading alot of posts here on the Hexa, I am led to believe, "more thrust = Bigger batt = more flight time". I saw this post :
http://www.diydrones.com/xn/detail/705844:Topic:849479?xg_source=ac...
James claims to get 25 mins flight time from 2x5000mah lipos in parallel. If this works, this is the route I am going.
I have an EnRoute hexa which is significantly heavier than a 3dr hexa (i think it's about 2kg fully loaded..maybe 2.2kg) with 1000kv motors and with a 3S 5400mAhm 3C and it gets 13min flight time.
I emailed 3DR support with the above info. Here's the response I received.
Hi Steve,
The results form those calculators always use either the worst case or a super conservative approach and never really give you real life values. When we fly 3DR Hexas with a similar configuration to yours, these are the observed results:
3DR Hexa, 880kv motors, 11x4.7 propellers
4s 4000mAh 30-40C
Hover: 14-15Amps
Max: 80A
Flight Time: 12:00min
Motors and ESCs slightly warm to touch.
3S 3300mAh 20-40C
Hover: 16-18A
Max: 60A
Flight Time: 10:00min
Motors and ESCs slightly warm to touch.
As you can see using a 4S will draw about 80A when in full throttle with the 880kv motors we sell. That means each motor is only drawing about 14A. Which is under the 243W motor max power spec, the 20 Amp ESC spec.
Adding a larger battery like you propose will give you a bit longer flight time but not more. Increasing the battery size only increases the flight time in an exponential manner as adding more payload will make the motors work harder at a hover state. You should be fine using a 30C battery. I hope this helps in your decision making when purchasing batteries. Let us know what performance your hexa gets.
Alan
can anybody give some help to a newbe? I'd sure like to get some batteries on order.