Misc Matching motors, esc's, battery (from YouTube)

[jdjeff]

Hi...I posted a question on the YouTube video with the same title. It was suggested I come in here to re-post the question.

A little background prior to pasting my original question: I picked up a used hex with brushless gimbal on rcgroups. It came as an entire package....batteries, transmitter, extra props, camera, etc. Up to this point, I have only been dealing with quads using 3 cell batteries. This hex came with 4 used batteries at 4 cells each. 2 batteries are 30-40C Turnigy 4000mah and 2 are 40-50C Turningy 5000mah Right now I can't figure out why the batteries are

a) getting much warmer than my 3 cells ever did
b) only getting a measly 4 or 6 minutes of flight time depending on which battery
c) puffing up by the end of flight

So as I was questioning this setup by the previous owner. I went to YT and found the video explaining batties esc's motors. Here's my question:

Ok...I went over to your forum and I did not see any multirotor threads. But maybe you can help.

2214 Century 700KV motors x6
30 Amp esc's x6
Current battery 14.8V 5000mah 30C
12x4 wooden props
3500 grams fully loaded with gimbal, camera, and battery

I bought this hex used. It has a brushless gimbal and a heavy lift kit. I'm questioning the battery selection (and esc's for that matter) by the previous owner. I only have that info on the motors and can't seem to find any data on them. The closest thing I can find are SunnySky's 2214-11 700KV. Even that spec sheet is iffy but they are talking 440 watts per motor.

The batteries that came with this hex are questionable in age and condition. But I'm only getting 6 minute flights and very warm puffed up batteries at the end of a flight.

I was looking at ordering a 14.8V 8000mah 35C battery and plugged in the numbers based on the calculations you gave in your video. I saw a much higher amp result and figured I'd be good to go with a "bigger" battery. But judging by the response you gave, I need to be looking for more C's. Now I'm confused. It seems to me that just based on the equation alone, raising either number (mah or C) will provide more amps.

I know multirotors tend to get away with lower discharge rates. At least I've read that in the past. So based on your response, I'm not sure what to do at this point. any ideas?

If I left out any specs, please let me know. Thanks.

 

[Tony]

Below is the answer that I tried to send in the YT reply but was denied because of the settings.

The multi-rotor section can be found in the link below.

Tri & Quad Copters

and you are right, you can raise the mah or the C rating of the battery to raise the amps that can be drawn out of it. However, raising the mah will add a lot of weight to the multi-rotor. Sometimes this is not an option.

If you are pulling 440 watts out of that motor on a 4s, then you really need 40a ESC's. You can test this with a watt meter and just do a static test. If this were mine, I would fly it and check the temp of the ESC's, all of them. If they are warm, they are fine. If they are hot, then go up to 40a ones.

On a battery, you are going to want somewhere around a 250a discharge rate. If you keep your 5000mah pack, then you would need at lease a 50c rating. But if weight is not an issue on teh battery, then the 8000mah that you posted will do just fine.

Hope this helps.

-Tony N.
Rc-Help - Your Rc Information Source!

I hope this answers your question and explains why I said to raise the C rating rather than the mah, unless you can afford to have a little heavier battery.

 

[jdjeff]

I would also like to add...the first thing that made me begin to question this setup was the wire gauge used on the distribution board. These batteries have 8 and 10 guage lead wires. The wire gauge on the connecting lead on the hex side looks like 14 or 16 gauge. And I can only imagine that was done due to a perceived challenge of soldering to the DJI distribution board. So I began questioning if enough thought went into the motors esc battery combo. And this is a Flame Wheel 550 frame.

 

[Tony]

If you are good at soldering, you can run some 10ga wire. It's good for something like 250 amps, but I have no idea what voltage that is rated at. But you are right, I would want that wire being larger than the ESC wires.

 

[jdjeff]

Ok...I got your answer...thank you. I did also forget to mention that I did take this hex up in the air 3 times now. And I actually did feel the motors and esc's when I saw how warm the battery was. And the motors/esc's were just about at ambient temperature. It was at that point all the question marks started circling around my head.

I don't want to rule out that these batteries are shot. This was a working multirotor at one time. My original intent here was to just increase my flight time. But then I felt how warm the batteries were with the puffiness...and I got concerned.

 

[Tony]

If the ESC's are not that warm, they you should be fine with them. So instead of 40x6, you are only needing 30x6. This can save you quite a bit on new batteries. Make sure to post up some pictures and video of this beast in the air. I would love to see it.

 

[jdjeff]

I will do that. This hex has a gothelirc gimbal and I talked the guy into selling the Sony NEX5N along with it. The gimbal is amazing. He had that set up perfect. I'm still searching for optimal video settings on the camera, but I have to say it's a HUGE difference from a hard mounted gopro. I would just like get at least 10 minutes out of it. That's not asking for too much I don't think. And more recently, I don't want it to go up in flames.

 

[jdjeff]

I was also wondering....I have some 3S 6400mah 40C batteries. I just did all the calculations. It looks like the 3S will work....assuming I calculated correctly. But I have some basic questions about dropping the cell count. What can I expect from a hex carrying that kind of load with a 3S? And second, on board there is a 12 volt regulator to power the gimbal. It is directly connected to the flight pack. What will happen to the output of a 12 volt regulator if the input drops below 12V? Or would you recommend a seperate battery or straight connection to the flight battery?

 

[Tony]

For a multi of this size, I would not try to run a 3s on it. Not only will you lose 25% of your motor speed, but you will be drawing more amps out of the battery. I would stick with the 4s.

As for the regulator, it will still regulate until it falls below 12vDC, then your actual voltage is what will be going to the gimble. Another reason to stick with the 4S.

 

[jdjeff]

Thanks again Tony...another mystery solved....thank you.

 

[Tony]

My pleasure

 

[Lee]

I would be leaning towards duff batteries.
My QAV500 on 4S 5000mah, was getting 10 to 15 mins easy when i first got it. Now the batteries are puffed and had a tonne of flights, I'm lucky to get 5 to 7mins.

 

[Tony]

One thing to remember Lee, this is a Hex, so more motors, more draw, less flight time.

 

[callsign4223]

That's true to a point Tony, however it's not as big a differential as you might think. Let me lead with this is all theoretical from playing with quad and hex power calculators.

The additional two motors will increase your power draw, however they need to spin at much lower rpm to maintain the same flight profile. From everything I saw playing with the calculator going from a quad to a hex only dropped the flight times 2-3 minutes while greatly increasing lift capacity.

I was really looking into this when I was thinking about the real estate photography thing before I realized how asinine the regulations are.

 

[Tony]

Do you really want to start that argument on here? I am pretty sure we have had one of these discussions and it didn't turn out too well hahahaa. But I do see what you are saying, but as you stated yourself, it does pull more power using more motors, that is pretty much the bottom line.

 

[callsign4223]

Hey, I said it's all theory.

 

[jdjeff]

Well I can say with a reasonable amount of certainty, that the batteries that came with this hex look (I won't say abused) but used. I have 3S batteries here that I have been using since April, and they at least still have that 'new' appearance. It's just too bad I don't have any 4S laying around. The other thing that I know is that Naza firmware 2.02 was installed on this machine. The only thing that goes against my theory of old batteries, is the owner told me to expect 8 minute flights. I asked if he tried any larger capacity batteries and he said he never desired to. So maybe the 8 minutes is accurate for this 5000mah battery, but maybe the batteries need to be replaced as well.

I ordered one of these. RMRC 8000mAh 4S 35C Lipo Pack [4S-8000-RMRC] - $89.99 : Ready Made RC LLC, Your full service FPV and R/C store!

I'm a little nervous about the C rating as these 5000 batteries on this hex are 40C. I'm taking a risk getting this new battery. On the bright side, the 8000 is only 166 grams heavier than the 5000. The previous owner seems to think that this hex will take more weight. Unfortunately, I never asked how old the batteries are or how many hours are on them. And I feel I bugged him enough already. I also ordered some new HXT connectors and I'm going to upgrade the hex side battery lead. The skinny little power lead got warm during flight too.

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I didn't mean for that link to show up the way it did. I pasted the raw link in the text box and that's what showed up. Not sure about TOS and advertising, but I can't edit the post.