Esc low voltage sensor tripping

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Ericehess

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Hey all. I upgraded my vector Sr 48 with a 60A seeking esc, atomx barbwire driveshaft, 35 mm metal prop and 4500kv goolrc motor. Using it with a 1500mah 2S ovionic lipo battery. When I run it it goes great for 30seconds or so then shuts down and restarts at half speed, the low voltage alarm is tripping. Battery new and fully charged and balanced. When I turn off the Low voltage sensor it runs great..goes about 40. The boat is about 17 inches so the 35 mm prop may be overkill. Could the prop be too big for the motor and be causing the low voltage sensor to go off? Doesn't seem to be bogging down at low speeds, gets up to speed quick. I ordered a 3200kv trackstar 380 motor to use with a 3s. Hoping the esc isn't the issue. The motor is a cheap Chinese one so I hope the motor is the issue.
 
So I'm not a boat guy but I know a decent amount about electric RCs in general. My educated guess looking at the electronics and battery that came stock vs what youve put in to it I would say your LiPo is inadequate for the amperage draw. You went from using the tiny little motor below to using a 380 sized motor. In addition to the motor can size itself being much larger it also almost twice the kv rating. Add on top of that the oversized prop and now you have a system that is drawing waaaaaaay more power than it did before. The problem is the lipo you're using isnt much bigger than the stock one. Its 1500mah instead of 1000mah and its true C rating is probably half of whats listed so we'll guestimate 25C and the old lipo was 20C which probably is a true C rating or at least closer to a true rating than the 50C the Ovionics claims. So I'm guessing the system is just drawing to much power from the battery and causing LVC rather quickly.

The only other things i can thing of would be a bad/faulty battery or esc.

Old stock motor taht came with the boat
PM1164_797-3-01__98488.1555589518.1280.1280.jpg
 
The stock was a 1000mah 3s lipo and I'm using a 1500 mAh 2s lipo. I use a similar motor with he same battery in an upgraded 1/16 redcat volcano and have had no issues. Does an increase in boat prop size cause more draw on the battery? Can this cause the esc to read a low voltage? I'm gonna try a smaller prop tomorrow and see if this makes a difference. Will check back in. Thanks for the help.
 
a increase in pro size will use more mah in running.. Id really check the battery if lvc is kicking in than thats were I'm looking..a cheap motor should not make lvc kick in.. that motor will need alot of millamps to run it whats battery C rate?
 
Batteries rated 50c. 1500mah. It works fine without lvc on. Could the battery have a bad connection causing sudden voltage drop momentarily perhaps?
 
The stock was a 1000mah 3s lipo and I'm using a 1500 mAh 2s lipo. I use a similar motor with he same battery in an upgraded 1/16 redcat volcano and have had no issues. Does an increase in boat prop size cause more draw on the battery? Can this cause the esc to read a low voltage? I'm gonna try a smaller prop tomorrow and see if this makes a difference. Will check back in. Thanks for the help.
I know the stock battery was 3s and you're running 2s. Running lower voltage actually increases amperage draw too. The Gool 4500kv motor according to specs I found online has a max wattage of 300W. So using Watts law (Wattage = Amperage X Voltage) We can see that on 3S if we take 300W divided by 11.1V = 27.02Amps. On 2S you have 300W/7.4V=40.54A. This does not take in to account for anything that makes the motor work harder like running a bigger prop. It takes more torque to turn the bigger prop which is why I brought up the fact that your replacement motor is nearly double the KV rating of the one thats in the boat. The higher the KV rating of a motor the higher top speed it has but that also means it has less torque to turn that bigger prop adding even more load on the motor comapred to a lower KV motor. Top speed and torque are inversely proportional in that the more top speed you want the less torque you will have and visa versa. So you can see how this system is pulling a lot of juice from the battery compared to the original set up. I understand your lipo is rated at 50C and I promise you it aint really 50C. C ratings on LiPos are a joke. Its a marketing gimmick. If you take a 2S SMC 7200mah 60C and calculate out the max amp draw using the 60C rating on the pack it comes out to 432A continuous. My car battery only does 450A in short bursts. When you take a brand new 2S SMC 7200mah lipo and actually measure the IR of the individual cells, then you calculate the real continuous C rating that the battery it can really only produce about 137A safely and continuously. Thats a true C rating of about 19C not 60C. Now all of that being said I can't swear thats your problem because like I said before I'm not a boat guy but I am an electronics/battery guy and from an electronics stand point its entirely possible that you're simply drawing to big a load from that battery causing the voltage to dip below LVC very quickly or if the ESC has over-current protection built in to it then it could also be tripping that and causing the ESC to temporarily reset. As for your running the battery in your Volcano that doesn't really mean anything because you're comparing apples to oranges there. Even if you were using the same exact motor, ESC, and Battery in rthe Volcano its still not a reliable example because the dynamics of use is totally different between the two models.

Could the battery have a bad connection causing sudden voltage drop momentarily perhaps?
As I said before, "The only other things i can thing of would be a bad/faulty battery or esc."

Have you tried other batteries or a different ESC for troubleshooting purposes? That would be my next step. That or using a lower kv motor. Something around 2200-3000kv just to see if the same thing happens.
 
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Wow, lotsa info. I understand all the kv ratings and torque vs speed. I was just wondering if an overloaded high kv motor could cause the battery to quickly drop below lvc set thresholds. My new 3200 kv motor just arrived today so I'll be switching out that motor and battery for a 3s. I am going to use that motor and battery in another boat though so I might run into the issue again, although the prop on other boat is only 30mm. Thanks for all your help! I'll let you know how the new motor works.
 
Wow, lotsa info. I understand all the kv ratings and torque vs speed. I was just wondering if an overloaded high kv motor could cause the battery to quickly drop below lvc set thresholds. My new 3200 kv motor just arrived today so I'll be switching out that motor and battery for a 3s. I am going to use that motor and battery in another boat though so I might run into the issue again, although the prop on other boat is only 30mm. Thanks for all your help! I'll let you know how the new motor works.
Yeah please do let me know. I'm curious. Also try using a little bigger mah rating LiPo if it will fit. The additonal volts from 3S and the more mah the bigger the amp load the lipo can handle. If you have something laying around. I hope that works out for ya!
 
Yeah please do let me know. I'm curious. Also try using a little bigger mah rating LiPo if it will fit. The additonal volts from 3S and the more mah the bigger the amp load the lipo can handle. If you have something laying around. I hope that works out for ya!
The 3s I'm using is 2200mah 25c. I'll post again tomorrow. Thanks again.
 
Got the new turnigy trackstar motor in. Will take it for a testdrive later.
 

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Nope, not so good. I still had the LVC issue using a different motor and a bigger 3s battery. It's either the prop or the esc I guess. Also the 3200kv motor overheated bad after like 3 minutes of use. So the original motor was an outrunner..I switched to an inrunner. What are the benefits to using an outrunner in a boat? They seem to overheat less and give more torque. Also they self right the boat much better. Can anyone recommend a good outrunner motor around 3000-3500kv?
 
its that battery if lvc is off and no issue then put lvc on and issue then battery is problem..replace battery Id go up in C rate..
 
It did it with the 2s 50c and a 3s 25c. Both are ovonic batteries. All my other batteries Are large 2s And won't fit so If have to buy some new ones I guess.
 
Well thats disheartening. That motor is listed for 3S use so I'm guessing the prop is too big for the motor and thats why it overheated. You may have to run it on 2S or downsize the prop but if its still doing the LVC thing then Id probably start looking at your electronics for issues. Sorry I couldnt be more help to ya.
 
Yeah I really hoped it wasn't the esc, wasn't cheap and is practically brand new. I can run it without lvc as long as I'm careful not to use for too long. Returning the turnigy..getting a 3000kv Propdrive outrunner..rated to 4s. I'll check back in once I figure some things out. Thanks
 
Yeah I really hoped it wasn't the esc, wasn't cheap and is practically brand new. I can run it without lvc as long as I'm careful not to use for too long. Returning the turnigy..getting a 3000kv Propdrive outrunner..rated to 4s. I'll check back in once I figure some things out. Thanks
If you decide to run with the LVC turned off in the ESC you can buy a cheap LVC alarm like this to let you know when the battery is getting low. Although if the system really is pulling too much current the alarm will just go off too. I guess that would be one way to test it though.

https://www.ebay.com/itm/223510182434?hash=item340a3eba22:g:pyoAAOSw4~1c1Lrx
 
Great, good idea. I'll order today. Thanks!
 
Got the 3000kv outrunner and ran it today with no lvc issues. Ran great, went about 40. After 10 mins motor was hot but not burning hot. Guess the inrunner was the issue.
 

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