I just have the feeling I'm not doing something quite right and could use some input from the more experienced quad owners :)
Last summer I bought a 3DR DIY Quadkit. Along with that, I also bought the Tarot Gimbal. Last summer I assembled the quad and got used to flying it. No real issues to report. This spring I mounted the tarot gimbal and now I'm having some issues.
First thing I noticed, after adding the gimbal, the quad became somewhat unstable, seemed to have a hard time keeping straight and level, it seems really off balance. I've tried moving the battery backward away from the gimbal to offset the added weight with some success.
However, the main problem I'm having is puffy batteries. The first batteries I bought were 3200mah eflite batteries. They work just fine on the lighter quad I built using a F450 frame (all other hardware is identical to what you get with the 3DR DIY Quad) but this heavier quad seems to be giving them a beating. I also tried a multistar 4000mah battery as it supposed to be for multirotors but it seems to puff up after flights too. The ESC's aren't very hot at all but the motors sure are pretty toasty.
Using ecacl, I input all the data pertaining to the 3DR parts (motors, esc) and it throws up warning about possibly exceeding power output of motors.
I'm wondering if the combo of motors and ESC's are not up to the task of dealing with the weight of the quad (AUW is approx. 2400grams) and they are demanding so much power from the battery that it is damaging it?
What do you guys think? I'm considering upgrading the ESC's and motors or should I use a 3s battery instead of the 4s I'm currently using?
Replies
Puffy batteries: Either you're pulling too much current or you're discharging them below their minimum. If you're discharging too far, the batteries are now trash and will not hold much of a charge (making the craft feel under powered).
If it feels under powered, going from 4s to 3s is moving the wrong direction. I seriously doubt the motors can be overloaded with the stock 10x4.7 props running on a 4s battery (eCalc agrees). Are you running different props?
Not over discharging. I have a battery alarm attached to the battery, plus each time I land I check where I'm at and it reports still around 3.85v per cell.
Discharging too quickly is what I assumed. I must not understand this part as the quad has 20amp ESC's so I assumed that is the most the motors would get. The eflite battery I have is supposed to have a 30c discharge rate.
"I seriously doubt the motors can be overloaded with the stock 10x4.7 props running on a 4s battery (eCalc agrees)"
What numbers are you inputting, because when I input all my quad data, I get the following warnings:
I'm inputting:
Model weight 2400grams
BatteryCell 3300MaH 25/35 4S
20 Amp ESC
RC Timer A2836-9 (880KV)
APC Slowflyer 11/4.7
A 20A ESC will not prevent a motor from getting more than 20A. The current rating only rates the max the ESC is expected to deliver without failing. In most cases this is the max continuous and the ESC can deliver more for a short period of time.
What motor are you specifying? I'm fairly sure that kit uses the SunySky 880Kv motor or equivalent. I don't own that kit, but the pictures on the the 3DR website show the SunnySky motor and the text lists it as 880Kv.
At max throttle, the 10" prop will only require 16A of current, which should be fine for both the motor and ESC. This current draw would be 64A, which is under the rating of your batter (96A). I see you hoovering at 62% throttle, which is a little high, but should still be flyable. A hover time of a little over 5min is not too amazing, but should be ok for fun flying.
Here's the link to the eCalc settings I used: http://ecalc.ch/xcoptercalc.php?ecalc&lang=en&cooling=mediu...
(I believe you have to be an eCalc member to use that link)
Have you tried resetting your ESC end points and doing an auto tune?
The motor I'm inputting is an RCTimer A2836-9. As 3DR doesn't specify the manufacturer, I had to search it out. I actually found it using the search function in ecalc. 3DR has changed it's website quite a bit over the past couple of months but at one point it showed AC2836-9 for that motor which I found on ecalc in the RCTimer dropdown menu, I can't find that model number in Sunnysky.
Oh... missed half of your message before replying...
If you actually have the RC Timer motors, then you're probably over current on them. Those are pretty cheap and of suspect quality (in my opinion). Do a google search for those and compare the pictures to what you actually have. They are very different looking than the SunnySky X2216 880Kv units.
I see you listed 11" props, that definitely helps your hover time and hover throttle %.
I did at first try running a search on "A2836-9" and the only ones that come up are the ones listed on 3DR website as well as some results for jdrone. Certainly nothing from SunnySky. I just looked at the 880KV Sunnysky ones and they do look a little different. If I am correct about them being RCTimer and they are over current, that would explain why they get so hot but does that also explain the puffy batteries?
Regarding the props, that's one thing that's really bugged me with 3DR. When you look at their website at those motors, they say the are rated for 11-12" props yet when you buy the kit, it ships with 10" props...found that odd.
I am going to order some Sunnysky 880KV motors and hopefully that helps with some of my issues, perhaps finding a battery that has a higher discharge rate will also help.
Given your quads weight, I'd definitely consider 12" blades at some point although you might want to increase to 30A ESC if you do. Hovering should be fine on the 20A units, but it could be easy to overload them accidentally.
The RCtimer motors are rated for 243w while the SunnySky are rated for 320w. This increase in power handling should help a lot with the extra weight of the gimbal.
Thanks for you help, it's greatly appreciated :)
I've already ordered new 30A Afro ESC from hobbyking. Sadly, they don't seem to sell SunnySky so I'm trying to find a good place to get them from.
Any recommendations for good American site to purchase them from?
No one at all?
Bumpity bump bump