Sudden Drop in Power

[kent83]

About 5 to 6 minutes into a battery, the heli seems to have a sudden drop in power -- I'm hovering about 4-5 feet off the ground, and it will drop vertically, sometimes touching the ground. If I let it sit for a bit, it seems to come back to full power. It does this with both of my batteries, so I don't think it's a battery issue. I can still fly for another 5-6 minutes, so I don't think it's the battery running down (and, the drop in power is sudden, not gradual). The heli is pretty steady in the hover, so I think my setup is pretty balanced. In reading other threads, seems like the ESC might be a suspect. Is there anything I can do to help figure out whether it's the ESC or troubleshoot to see if it's something else? The ESC is always hot after a flight, but I don't know what's normal "hot" and what isn't. The heli's all stock parts, by the way.

[v2heli]

What are the Battery Specs?

It sounds like the ESC cutoff.

V2

[sutty]

I've never suffered from an over heating ESC, but I have read lots of threads about it and it sounds to me like maybe this is happening to yours. Could you try re-positioning it, to create additional cooling, to see if you can alleviate the problem at all. If you can and the situation improves then obviously you can decide on a final fixed position, for optimum cooling, or you can decide to upgrade to a better ESC. Maybe, as a temporary test measure, you could mount the ESC so the heatsink was sticking right out from the side of the helicopter, directly in the downdraught from the rotors. If you do this and there is no change in performance then it would seem unlikely to be an issue related to cooling.

[GCK]

If you are running the stock ESC then I will bet that’s your problem. I had the same issue. Once I got to the point that I could hover more then a couple minutes the helicopter would drop to 50% power. It’s doing this because the ESC is over heating. I took the stock ESC apart and found that not only where some of the mosfet’s not making contact with the heat sink but the heat sink was attached to the mosfets with a thin layer of double sided tape. Not a very good thermal conductor. I fixed mine by removing the double sided tape and using Delta Bond 155 (thermal conductive epoxy) to attach the heat sink to the mosfets. After redoing the heat shrink around the whole assembly I cut out a section around the heat sink area so it would be exposed to the ambient air around it. I since replaced the entire ESC with a 30A with an external switching BEC from Hobby wings. No trouble since.

[kianhon]

Is the ESC, my Dynam 30a did the exact same thing to me. What ESC you using? If is the stock one, then is time to change before it burn you heli.

[Jonnyheli]

Hold on I think everyone is missing the point. It sounds to me like he is having a normal power drop from the ESC. His gear mesh might be too tight which will strain the battery, motor and ESC.

I say, before you try anything or buy anything I think you should undo the 4 big allen screws that go into the motor mount plate and try and push it back then do the screws back up. If your pinion gear is too tight against the main gear it will affect your flight time.

Also, just to be on the safe side. When you do have the powerdip please don't carry on flying because if you discharge your battery it will puff up and it can become dangerous. Im not saying it's definate but just be on the safe side.

-Jonny

[v2heli]

Great Point, Jonnyheli.

It sounds like normal cutoff.
The capacity of the packs is important to know here.

6 mins on a 1500Mah pack would be a great fly time.

V2

[kent83]

Thanks for the suggestions. I'm running on the stock Esky battery: 1800mah 3S 11.1 V 15C. I'll try adjusting the motor and see if that changes the pattern. If that doesn't work I'll follow the suggestions for cooling the ESC to see if that makes a difference as well. What's a reasonable flying time for this battery? I know you're not supposed to run the batteries down too far, so I fly until I notice the gradual drop in power starting after about 8-10 minutes or so (which feels very different than this sudden drop). I'm just hovering at a steady height at about 60-70% throttle -- I'm still at the tail-in stage.

Thanks!

[GCK]

The above mentioned things certainly warrant taking a look at. But if I’m getting the correct idea from your symptoms I’ll still bet its the ESC. On my stock ESC when I reached the battery end it was a noticeable but gradual reduction of power. When the ESC would over heat it was a sudden drop to 50% power. The stock ESC has over temperature protection at 95 Deg. C. But may be if the gear mesh is to tight making everything work harder your ESC could over heat because of that. Easy enough to check.

[Ian 777]

Possibly both problems, that's a great tip for improving the cooling efficiency of the ESC. GCK:thumbup:

[Jonnyheli]

Kent83, are you sure your battery is 15C mine is 20C :P. Mine is stock, 11.1v 1800mAH 3s.

Maybe I am wrong but it says Discharging rate 20C on mine?

-Jonny

[kent83]

Thanks, Johnny. I got my second battery at ka planes, and it said 15c on the Web site:

http://www.ka-planes.com/inc/sdetail/3470

I just looked at the battery and don't see the discharge rate on it. I checked a Belt CP page on the Web, and it said 20 c in the product description, so you're probably right. I adjusted the motor as you suggested and used the paper technique as shown in one of the setup videos. I also removed most of the shrink wrap on the heatsink and still had the same problem. I let it cool for a few minutes, and it flies OK again, then power drops again after a few minutes flying time. So... probably the ESC?

GCK -- thanks for the pointers. I looked at Hobby Wing and was pretty intimidated by the choices (BL vs. Brushed?). Can you recommend a specific one?

Thanks all for the help!

[kianhon]

Base on what you said, then I guess is definitely you have a bad ESC.
If you are flying a Esky Belt-CP then is a Brushless ESC you need. Remember, is good to get yourself atleast a 30amp ESC for your belt. Below are some cheap but good ESC.

Dynam- I avoid this because I got one that failed on me at 1st use, it gave me the power reduction problem that you are having now. But many said it worked out for them, so may be I just got a defected one, I donno and I'm avoiding it in the future.

Hobbywing- the one I'm using now, worked out for me so far.

GWS - some says is bad but my fren is enjoying it.

All above cost between $25-$35 and are known for their performance. If you wanto to spend more for an ESC then I have nothing to share cuz I'm a cheapo :YeaBaby:

[GCK]

Kent83, The part number for the ESC I use is 30A-OPTO-UBEC. It’s the Pentium Brushless ESC rated 30A + 2A UBEC with 5V or 6V output from HobbyWings. I just left the BEC set to 5V output. The cost was around $35.00 or so. You will need to order a new deans connector and the barrel connectors as there is nothing on this ESC for terminations. Or you could remove them from your old ESC and solder them on to the new one.

On your stock ESC simply removing some of the heat shrink around the heat sink is not enough. If you take it apart I’m sure you will find as I did that the heat sink is not making contact on all of the mosfets. Also the double sided tape used will not be of much help in conducting heat to the heat sink. You would need to remove the tape and clean the heat sink up real good. Then apply Delta Bond 155 (Thermal conductive epoxy) to each of the mosfets and stick the heat sink back on. Once the epoxy dries then reheat shrink the assembly and then cut away some of the heat shrink from the heat sink. Personally I think you would be better off with a new ESC.

Good luck and let us know how it works out for you.

[c_cormier]

kent83 and Jonnyheli,

I have the same situation on my Belt CP. Sudden loss of power after hovering for a bit for no aparent reason. I have a lipo alarm that typically goes off after about 7 min or so.

I have 2 batteries from esky the once that came with the heli is a 15C and the additional battery I purchased is a 20C. I though something was wrong with my batteries, because one was slightly larger than the other.

I am going to look at my ESC to see if it is overheating and replace it if necessary. Thanks to everone for the tips and advice.

http://www.helifreak.com/showthread.php?t=57176


-Chris

[thunderhead]

Castle Creations is all I can say. 25amp Pheonix. Awsome. Spend some money! Cheap is Cheap. If you get the Castle link to go with it you can set up all your parameters via your PC. These ESCs rule. SPEND some MONEY!!!!!

[kent83]

Thanks GCK - very helpful, and I ordered the ESC yesterday. I soldered a new Deans onto the second battery I bought a little while ago (Finless Bob's video was really helpful), so I'm ready to try connecting the ESC. Good tip about the extra parts. I did look at the CC ESC -- thanks for the suggestion, Thunderhead -- but I just ordered the Tower 9g servos and some other parts (trying to build an inventory to reduce downtime between crashes), so budget is a factor right now. Maybe I'll move up when I get good enough to really fly the heli and where I even know what the parameters should be. BUT, here's a new twist on the story. One of the new parts I ordered were the Align 315 Fiber blades. I just had my first flight with the blades -- the heli seemed much more responsive which took a little getting used to. At the same time, there were long moments where it was just hovering rock-solid and it seemed like I had to do very little on the sticks to keep it steady. I also had some tail shake with the stock blades (I almost posted a thread yesterday asking how to adjust for that) -- and the shake is now gone. AND .... I got through the whole battery without having the drop in power! So I'm figuring that the efficiency of the new blades is reducing the strain on the motor/ESC? Does that make sense? I'll still install the new ESC -- I figure as soon as I learn to move beyond a steady hover the demands on the motor and ESC will increase, so it's a good upgrade to do. But, interesting that a blade change made the difference at this point.

Thanks again everyone for the help and suggestions. This forum is just amazing!