3S Lipo Battery Issues

Have a couple issues I'm trying to sort out on a zippy flightmax 5000mah  20C lipo.

I had an F450 quad running the battery with ok flight times and the battery was doing ok. I crashed the F450 due to mechanic error ( GPS fell off ).

Now I've rebuilt the F450 into and F550. The Battery gets about a 4 minutes hover time before the APM Fail Safe brings it home due to low battery. The Fail Safe is set at 10.5 volts with a 600 mah reserve. same as it was in the F450.  The issue I'm having is the battery voltage comes back up to 11.5 volts and all the cells are at storage level 3.84 - 3.85 volts after the flight and take a little over 2000mah when recharged. My guess is the 20C battery rating is to small for a hexacopter and the battery just can't keep up.

I just purchased 2 Zippy 6200mah 40/50C batteries and a parallel plug for the hex at hobbyking hoping that will cure the hover time flight issues. Just waiting for it to get here. In the mean time I'm been trying to calculate the hex build at http://www.ecalc.ch/xcoptercalc.php, what a pain...

Will to high of a C rating on a lipo battery fry my motors ?

Here's the specs on the F550 hex.

1728 g F550 total weight without batteries (weighed by local post office)

902 g 2 3S 6200mah 40/50C zippy compact lipos

A2212 13T 1000KV motors, equivalent motors  AXI 2212/26 920 KV

10x4.5 SF propellers, however I have 10x6SF propellers coming for extra needed thrust.

hobbypower 30A ESCs

Here's the best data sheet I could find for the A2212/13T Motors.

I went  with the hex for redundancy in case of motor failure but am not sure if higher C rated lipos will fry the motors or if I'll have the redundancy.

It would be great If anybody can chime in to help give me some peace of mind.


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  • sunnysky also has a efficiency chart for these motors that looks pretty good too.

    After a lot of research I think I'm going with 12x4.5 props. I really wanted to go with 13 - 14 inch props with a 3 - 4 pitch but  options are limited for using the flamewheel and larger props.

    The RCT800 arms would have allowed for 14 inch props but the motor mount holes won't allow for the v3508 motors unless I only used two mounting holes, which is not an option.

    The only other options I could find that would work were aluminum arms that have slotted mounting holes. There are a lot of pricey aluminum arms out there that turn the F550 into an F650. I decided to go with the cheapest option at googluckbuy with a cost of a few extra grams per arm. They also had a F650 frame kit with the aluminum arms that came out to 1 - 2 dollars more than purchasing the arms separate, so that's what I purchased. Buying the kit gives me extra mounting plates which will be the weakest link in the hexacopter. I might pickup motor extension plates later so I can use 13 inch props.

    Here's the specs for using 12x4.5 props with 3S lipo and 4S lipo

    12x4.5 with 3S Lipo 3702928721?profile=original

    12x4.5 with 4S lipo


    13x4 with 3S lipo


    13x4 with 4S Lipo


    • The new V3508 motors arrived today. They look very nice. I'm not totally sure if they are real or fake yet. The engraving on the motor looks exactly like the pictures on the sunnysky web site, except the sunnysky website image shows KV: 700 II and the ones I have say KV: 700. The box seems to look like the factory box listed on sunnysky website. I was able to see the bearing number on the bottom of the motor. The bearing is a Japan EZO 694Z . I wish my new arms and propellers were here so I can try them out.

  • Well, I do a lot of Ebay shopping and I have a feeling that these sunnysky v3508 are the real deal. These motors kinda amaze me that 6 v3508 motors on a 4S lipo can lift a little over 20 lbs with 13x4 props. any suggestion on the optimum prop size for these motors on a hex?

  • Ya, I crashed the hex the other day not to bad when I was doing my first flying/recording test with the FPV. The weather was changing and I was in loiter when the hex started to climb and drop about 10 feet a few times. It looked like it was going to start a fly away straight up when i hit stab mode and forgot my throttle was at 0. I full throttled before it hit the to of my van and a gust of wind hit it at the same time and sent it through the trees. I was lucky and broke 1 prop, 1 landing skid and got a nice video set to the music Free Bird. I did notice I need to add an L C filter to the FPV. I have replacement landing skid on order from china, but in the meantime I learned my soldering iron also likes to bond plastic. So the landing skid is in one piece for now.

    Going over your motor recommendation for the hex. I was leaning toward Tarot 2814 700kv motors for about 16.00 each from china, however I couldn't find any real specs for them, which turned me off.

    I did run into what looks to be a very good deal on EBAY for 7 New SunnySky V3508 700kv Brushless Motors which I bought on ebay for $150.. After running calculations on eCalc.ch these motors seem to be a perfect fit for the hex and will still run with my 30A escs. The motors maybe even be way over powered for the hex,  which to me is a good thing. I guess I need to find replacement arms for the hex as the V3508 motors won't mount to the F550 stock arms and the motor needs bigger propellers for it to function properly. I was leaning towards the RCT800 arms or the RCT800 frame kit. I also found some aluminum arms on ebay. Propellers are another story, seems the longer the propellers are the more expensive they get.

  • After reading your reply I spent the last few days researching and playing with different combinations on http://www.ecalc.ch/xcoptercalc.php.

    Since 10" propellers are the biggest propellers that will fit the hex without raising 3 of the motors so the propellers overlap. my other choice is to upgrade the arms so the hex is greater than 550mm. didn't really want the copter bigger as I was happy with the F450 size. But  that seems to be my only choice, I was looking to upgrade the arms for the F550. I kind of like the looks of these RCT800 arms which will increase my prop size to 15", however is will also increase the copters weight. My calculations are the AUW will go from 1728g to 2450g w/o battery. selecting affordable motors for the new design seem to be a real hit and miss. Some motor prop combinations will give it a 8000g payload capacity and not much more hover time than 18 minutes @ 12000mah, but usually the combinations overload the 30A esc I already have.

    Far as striping weight from the F550, not really an option as I really want to add an OSD module, Sonar module and some leds. It doesn't seem like it when building a copter the weight adds up fast with a few grams here and there.

    I set the F550 to ignore battery failsafe and flew is a coupe times to get an idea of what the battery was really doing and so it wouldn't fly into the bottom of the trees.   The zippy 20C 5000mah was to 12.5 volt when I  I took off. Telemetry showed between 25-30 amps hovering in STAB mode and hit about  40+ amps when I jumped on the throttle. I flew it until The voltage showed 9.8 and when it landed the voltage went up to a stable 11.3. it was about a 7 minute flight. The battery took 3200mah when I recharged it. The battery is about 30 days old.  The symptoms kind of remind me of a car battery CCA rating to low for the application.

    Here's a volt graph of the flight.


    Here's the hex, it really doesn't have much on it.


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