My new Banggood Mobula 6 was flying fine with the supplied 300 mAh HV LiPo PH2.0 connector. I bought some Tattu 300 mAh BT2.0 HV LiPo's and replaced the PH2.0 connector with a BT2.0 connector hoping to reduce voltage sag and increase performance. Now when I throttle up to take off it continues to climb even with low throttle stick. Note that I have complete control of the 3 axes just with runaway throttle. I can physically hold the whoop down and see this behavior, once the throttle is advanced and returned to "idle" the motors gradually continue to speed up to full power. If I load a discharged battery or run the battery down to approximately 3.7-8v at some point the throttle begins to operate normally again. In Betaflight the max voltage is set to 4.4V. Why would swapping the connector type do this? Or why would the lower resistance and therefor higher voltage of one connector over the other cause this?
I inspected the frame and board and I cannot see anything out of ordinary, nothing broken.

It does have one issue out of the box in that the #1 motor is "tight" compared to the others when turned by hand. I often have to arm it repeatedly before it spins up. But once it is spinning the quad flies normally. Before the swap to BT2.0 that is. I have a ticket with Banggood to see about getting a replacement for the 0702 26000Kv motor with issues but it is proving to be anything but easy. A picture of the one propeller not turning is not enough. Now they want me to post a video on You Tube. Anyway I do not think this has anything to do with the runaway throttle because it only occurs now after the connector swap.

FWIW the quad flies great, great performance and range with the ELRS Rx. But the camera is sub standard. Mine is grainy, the colors and contrast are stark with low resolution. Maybe they are not set up well from the factory. I will investigate that once it is flying again.

Likely the more conductive connectors are allowing more current to flow, tipping over an already iffy set up.  That's almost a given.

You could try a throttle limit in Betaflight, but if you have a known issue like a stiff motor, then that should have been and still should be your first response, from new, return to dealer. 

They will ALWAYS ask for a video, its standard policy, just send one. You have though done mods, a bad move when claiming faulty supply.

At minimum a very close inspection for the reason for the stiffness and that being cleared should be a priority before you damage the thing, i.e. don't try to fly it, only test carefully!

Other than magnetic "cogging", which would be closely even across all motors, there should be no stiffness when unpowered, with the prop on that motor tending to flick ahead to the next magnetic alignment when rotated by pushing around with one finger.

its not anything about the bt2.0, its battery performance. better performance can neeed other filter and tuning settups.
you could try to increase filtering and lower the pids a bit, or just pick a tune for the mob 6 and test it.

seems happymodel provides usless lipos, that might be the issue you get: but you can be lucky, your mob6 will be a different animal on tattus ;-)


the mob 6 doesnt has a high current, it might not give benefits from the bt2.0.
bt2.0 is mostly hype, top performance requires low weight, therefor an ultralight whoop with low current can perform better on ph2.0.

while banggood might provide a solution, i dont believe there is anything else wrong than happymodel batteries xD

Sort of like going from bottom of the pile Lipos to elite level Lipos in one move. Besides being able to address more current, it shouldn't have made a massive difference. So your choices are tune it or just learn to fly it. All my quads that are 1S use BT2.0 and they all fly really well on stock tune. Maybe it is hype, but I have always flown BT2.0 and never experienced the voltage sag that people talk about on PH2.0, although they still sag on BT2.0 at the end of the pack.

So my suggestion is just go fly it. it will take a week or two to get used to the throttle position, but I wouldn't throttle limit beyond maybe 80-90%. Probably all that is now happening is that throttle curve is no longer so flat and straight. When you give it throttle it now reacts instantly and you get an almost vertical line on the curve. Enjoy it. You can now do more aggressive throttle punches, probably fly outside with ease. The Tattu packs should last a lot longer, so expect to get some more flight time. This is how it should be. Control shouldn't be sluggish, it should be rapid, agile and nimble.

On a side note you could try changing the throttle limits in betaflight.


That will make it a little easier to control, but you will still need to learn the new hover position. If it is now 15%, then only flying it will teach you that.

Today I removed the BT2.0 and put the stock PH2.0 connector back on the quad. Running the the Happymodel batteries, it flies fine again! I made up a little transition piece to try tomorrow so I can use the Tattu batt BT2.0 with the Mobula 6 PH2.0 via the transition piece, then we will know if it is the connector or the batteries that cause the runaway throttle.

This is nothing to do with skill. The quad is unflyable with BT2.0 connector and Tattu batteries, once the throttle stick is advanced it just goes straight up, accelerating on its own to full power, and lowering the throttle back to idle stop will not stop it from flying away, the only way to get it to descend is disarming it and catching it, what fun! But why that is happening I do not know. Maybe it can be cured in Betaflight.
I agree that replacing the tight motor is needed. I will send a video to Bangood tomorrow, maybe a new ticket, if the motors are available from other sources I may just buy one. I had originally planned to buy a set of Red Rocket motors for it but not if it has a faulty board.

it happens because of dramatic difference in power to weight. therefor the pids and filters are wrong, wrong filters cause noise and it can come to the runaway you are getting.

to high i-term and noise from high p and d term values, that might be the issue woth the tattu lipos

OK I used my little home brew connector to transition from the Mobula 6 PH2.0 connector to a BT2.0 connector so I could try the Tattu battery. The runaway throttle happened again. So I know now that the runaway to full throttle is being caused not by the connector swap but by the battery swap. I've updated the thread title to clarify that. It must be a software issue as some of you said. I'm confident now that it can be tuned to run properly.
Before I continue pursuing this repair I will replace the "tight" motor. I can get it running by spinning it by hand or massaging it to do these tests but it's not right. Once that is done I'll load one of the Mobula 6 tunes from Betaflight and report back. I'll compare the PID parameters discussed above.

Hey man, you're getting a little more current through that connector now. Perhaps the current sensor divider will not understand this increase a little. Betaflight is an extremely stupid system when it comes to all sorts of sensors. It might be worth using dividers from Betaflight, or reducing the upper throttle limit a little on the PID - Throttle limit tab.
On my Mobula7 i change batteries from 300mAh to 550mAh and do not see any problems with the same connector.

Thanks, I just ordered a set of motors, I'll be trying all this stuff when I get them. They're the same Happymodel SE0702 26000 so I'll have a few extras.

its one of the most lightweight motors, its nice on a low weight whoop.
the durability of these motors, the shaft, isnt on our regular level. they are on the edge of usable, some buddies love them and some wouldnt even use them if its a present.
next to the shaft weakkness, from their low weight they can provide nice nimbleness and allow to get the benefits out of the high kv. it can give an ultralight whoop which cant be copied in flightdynamics.
i believe betafpv has a lightweight 0702 motor, in two versions - i dont know their durability but it would be the only comparable motor

spares are nice, you might need them :-) if they doesnt hold up long enough, dont get frustrated, a littlebit more heavy 0802 motor would provide another durability level.

I replaced the bad motor and the flyaway with the Tattu battery was worse, just arming the quad it took off, so that was not the problem. I loaded a tune from the Presets page in Betaflight, "whoop race tune by Justice" and the Mobula 6 is flying normally with the high performance battery!

@hugnosed_bat your comments about PID's above went right over my head, I need to study how those work, but suffice to say the PID's in the Preset tune are completely different than the ones that came installed on the Mobula 6. Mostly way less, a couple way more (feedforward), and extreme right or left slider positions versus the stock setup with them all centered. I learned a lot today!

I can't wait to fly this now and see how it goes.

https://betaflight.com/docs/wiki/archive...orward-2.0

betaflight defaults are made for 5inches, a lot ways to get a whoop flying better.
the battery of happymodel does perform realy bad xD soo bad its tuned totaly wrong therefor xD

what flighttimes and performance difference do you het on the tattus ;-) ? they are another league :-)

I got a bunch of flights on my Mobula today. I get the hype now, it flies really well, very confidence inspiring. Like my new Fractal 75, it just goes where you want it to
So, alternating between the Happymodel batts and the Tattu batts was an eye opening experience. Just punching out on take off and the first few seconds the Happybatts are down to 3.7 but the Tattu stayed above 4.0. I could get a little over 2 min with the Happys getting down to 3.3 inflight and recovering to 3.7 but the batt low warning is on the whole flight. Meanwhile the Tattu could go about 30-60 seconds longer but with good voltage until dropping at the very end and giving a warning. Also the Happy vary quite a bit, one of mine is useless, but the Tattu's are all good. FYI the Tattu are straight BT2.0 and the Happy have to go through a PH2.0 to BT2.0 connector.

mine was that the battery was loose i added some foam and not more issues

Weird, maybe that was it? I don't remember them being loose but who knows.