Popeye

[Texas FE Boater]

So testing a new Popeye out. TX =Radiomaster MT12 ELRS RX= ER5C-V2 ExpressLRS PWM Stock ESC and motor. Runs great on 4s. Runs great on 6s till full throttle then I lose radio and control till failsafe kick in. I'm guessing this is a brownout and losing too much voltage from rx , and need to install a cap or Castle BEC. Just want confirmation from you guys on this please. Also on the Castle esc's there are 2 different BEC ratings. When using these would it reduce the need for the Castle BEC since they provide more to the rx. Thank you for your help. Yes I know when running 6s to only run a couple quick passes and to watch temp closely. I also had this same issue on a Oxi Rigger with same radio and also only on 6s. 4s ran fine. It's got to be these rx's needing a BEC or cap in my opinion.

[Xrayted]

There is a significant increase in current draw when using 6S vs 4S if all else remains the same hardware/prop on the boat. Your ESC is likely going into over current shutdown when you are going wide open and pulling the most current, or the battery voltage is sagging below the low voltage cutoff limit. You wait a second and then suddenly the model will typically run again once the load is removed.

6 vs 4S is 50% more RPM at the prop, and you may need to run a smaller or lower pitch prop in order to keep the ESC from shutting down. You can also experiment with the ESC low voltage cutoff setting and lower the value or completely shut the LVC off and see if the problem goes away, however you must be careful and keep and eye on the battery voltage so you dont run things too low and possibly puff the battery

[Texas FE Boater]

Thank you for your help. I know running this high KV I will need to stick to short speed burst and Moniter heat and use appropriate size props. I?m actually getting the opposite of a shut down. At full throttle I lose radio and esc going full out untill the failsafe kicks in after a few seconds. Others have told me I need a CAP or Castle BEC on the rx cause it?s drawing power from the rx and causing a brown out. I hope this is understandable as I am not good at putting thoughts into words. Thanks again.

[Texas FE Boater]

I would be happy if it was a shut off because losing control is not a fun thing. Id rather it shut off then go full on power for a few seconds. Lucky so far I?ve been far enough from shore for failsafe to kick in before hitting shore.

[Xrayted]

Ah, so the model is losing radio and speeding across the lake on its own power, and is luckily shutting down either for overcurrent at WOT or LVC before it runs into the bank of the lake? You need to stop running this boat immediately if this is the case!

What voltage is the internal Castle ESC BEC set to? You can try to lower the BEC voltage if set to its highest value as test to see if anything changes. The higher you run a BEC voltage, the more current is drawn by the servo because its moving faster with more torque, and that extra work doesnt come for free, so its possible that your RX voltage is dropping below the reset threshold due to higher servo current. You have a Castle ESC, so you should be able to log the BEC voltage and see what its min value during the run was.

You could also temporarily bypass the internal BEC, and run a direct 2S lipo to the ESC (assuming your RX and servo is rated for 8.4V) and see again if the issue stops which would indicate the BEC.

You could also plug a single CAP into any available slot on the RX to help smooth any BEC dips when using your current setup and see if the issue stops https://www.amazon.com/Spektrum-SPM1...ps%2C74&sr=8-1

[Texas FE Boater]

Correct. Boat is benched till this is figured out. Esc is Seaking 180a. I was going to bypass the esc bec and install a stand alone Castle BEC from OSE. Was told this or a cap should solve the problem. Reading a little bit on here and other forums has scared me from the Cap because of fires.

[Xrayted]

Ok, that changes things a lot then. It cannot be the BEC if the same boat runs fine on 6S wide open using a Spektrum TX. One thing has nothing to do with the other as the BEC remains the same in both cases.

That points to the Radiomaster RX being the culprit, and either its faulty or more sensitive to browning out at a higher voltage threshold than the Spektrum. The easiest way to keep a RX from browning out is to use a single cap plugged into the RX like I posted. This is exactly what they are used for, and no, you dont have to worry about "explosions".

That only happens when they are abused, or not rated for the voltage being applied to them. CAPS are all over your ESC already for the very same reason, to smooth out battery voltage ripple, but the ESC/BEC is not the source of your issue if it all goes away when you switch TXs.

[Texas FE Boater]

Tx and rx have been set with same phrase code(binding code if you?re not familiar with this radio). Power setting have been raised on tx and matched on rx.

[Texas FE Boater]

Thank you. That?s the confirmation I needed. I will get one and try that. Do you gain any advantage using more than one or should only use one Cap?

[Xrayted]

Ive never used more than 1 cap in any RX. If you need two, you would just use one with a higher rating, but it will be bigger. The one I listed should be fine.

[Texas FE Boater]

Thank you very much.

[Texas FE Boater]

I think im going to order a carbon version and dedicate it to 6s. That being said I will just run this one on 4s. Do you think I should go ahead and use a cap on 4s just to be safe? I ordered a couple caps and a couple Castle BECs being they are relatively cheap.

[Xrayted]

That's totally up to you. Having a CAP in the RX certainly won't hurt anything, even if its not needed. I use one in all of my RC helis because its common for there to be RX voltage dips due to the sudden reversals of the servos, and the fact that there are always 4 of them working at the same time means its possible to have near 20A momentary spikes that can dip the RX voltage. Many air ESCs used for helis come with a CAP in the box to plug into the RX if this is an issue, Hobbyking being one of them

Just keep in mind that carbon fiber is conductive and blocks radio signals, so the antenna must be well outside of the hull and up away from it.

[Texas FE Boater]

Can I run both a cap and the Castle BEC for added peace of mind?

[Xrayted]

You certainly can if you wish to