newPTboater

I'm new to electrics and and having a problem. I am building a Dumas 1/20 scale PT boat. I have powered it with the dual motor kit from Mack Marine. The motors will run for about 1 minute and then one will quit (and sometimes reverse direction). My set up is as follows: 2 12v 5 amp motors, each motor is hooked to a Proboat ESC, each ESC has a 10 cell, 12V NiMH pack attached to it. The ESC are connected with a Y harness which is hooked into the reciever. I am using the BEC function of the ESC. I have tried running with one ESC switched "on" and both ESCs switched On".. I always get the same result..the motors will run for about a minute and then one will quit and sometimes even reverse. Any help or suggestions would be greatly appreciated..I'm stumped.

Tug Guy

The first question I always ask on an electrical problem is did you charge all batteries and transmitter/receiver before running the motors?
Do these escs require a setup procedure before running for the first time?


Tug

newPTboater

Yes, the batteries were fully charged. The only set-up for the ESCs is to move them to full forward and full reverse when you turn the system on.

LtDoc

newPTboater,
Did you disconnect the BEC in the second ESC? Using one BEC is fine, using both leads to problems.
- 'Doc

subsinker

My Feedback: (61)

Hi,

I am not terribly familiar with the MACK motor setup but 5A sounds a little bit low to me. Most motors generate much more than that while under a load. If you have checked your ESC's and they seem fine I would tend to lean more towards one motor drawing excessive current. Look for any binding or if you have access to a clamp on ammeter, check the current draw from each motor. If all else fails, change the escs around and see what happens. If the problem stays with the same motor then obviosuly you have either a motor/ alignment (or combination therof) problem. If the problem magically goes away or switches motors then you have an ESC problem. I have used Proboats ESCs' for a couple of years with varying success. For $40.00 you can't beat them, but I have had one or two that from the get-go were nothing but trouble and were replaced. The only other thing I can think of is that by using NiMh batteries, they do not have the ooommph that NiCds do. If your boat requires high current draw those batteries may not work for you. Thats only an observation and I cannot say for sure thats even an issue here. I have seen those types of batteries cause problems though.

Hope this helps,
Pete

newPTboater

Doc, .. I think so.
The ESC has a "on/off" switch that leads into the sealed ESC. I assumed that this turned the ESC (and BEC function) on/off.
I would turn "on" one of the ESCs but leave the other one in the "off" position, but I never physically disconnected anything.

I have also tried leaving both ESCs in "off" and hooking up a receiver battery pack. When I do this, only one motor spins.

Tug Guy

Is it possible one of the connectors or wires is shorting out and not keeping its connectivity?

Tug

LtDoc

newPTboater,
That 'ON/OFF' switch turns the whole thing on or off, not just the BEC. The only way I know of to disconnect the BEC in one ESC is to literally disconnect the thing. Clip that wire going to the receiver. You only need two wires going to the receiver, the 'signal' wire and the (-) wire. The BEC wire supplies power ~to~ the receiver, the ESC get's it's power from the battery connection. Just to be safe rather than sorry, I'd get someone else's opinion about that before doing any wire clipping. (Not that I think I'm wrong, just chicken since I'm not familiar with your ESC.)
- 'Doc

newPTboater

Thanks for the advice. Since the ESCs are hooked to the receiver via a Y harness, I could make the cut in one of the legs of the Y harness, at least that way, if I pick the wrong the wire (hope not!) I'm only out a Y harness, not an ESC.
I plan to line up the ESC lead (3 wires) next to a servo lead (2 wires) and I'll cut the one that doesn't match.

subsinker

My Feedback: (61)

PT,

You don't have to cut anything! All you have to do is to use the point of an x-acto knife and carefully remove the center wire from your "Y" harness. That will effectively remove the BEC circuit from your receiver/ESC's. Just remember though, you will have to have a battery pack to your receiver. That will power the receiver as well as the servo(s)

Pete

newPTboater

OK Pete,
The center wire it will be. If I remove it from only one "leg" of the Y harness (effectively removing the BEC function of one of the ESCs) will the remaining BEC provide power to both ESCs? or do you think it's best to remove the BEC function all together and just go with a reciever battery pack?

LtDoc

The receiver doesn't supply power to the ESC. An ESC with a BEC supplys power to the receiver instead of the receiver having it's own seperate battery pack. Cutting the BEC line from one ESC will take care of both ESC's trying to supply power which will cause problems (doesn't really matter where you cut, at the ESC or in the 'Y' adaptor leg going to that ESC. And you're right, since the 'Y' adaptor is cheaper than an ESC, cut the 'Y's leg.). Stopping one ESC from it's BEC function and allowing the other ESC to use it's BEC function will work out fine. It may not 'cure' your problem, but it will certainly eliminate one possible cause of it.
- 'Doc

PS - Maybe I should take that just a little bit further. The ESC which uses it's BEC function does supply power to the receiver and everything the receiver supplies power to (servos, lights, whatever). So, the battery connected to the ESC doing the BEC'ing will discharge slightly faster than the other ESC/battery. That has both good and bad qualities, depending on the ESC. If the ESC has a 'fail safe' feature, meaning that it will still supply power to the receiver when it's battery is no longer able to do that and run the motor. That means that the second ESC/battery can get the boat back to shore (if both batteries are the same and equally charged to start with). The bad part is that if the ESC doesn't have that 'fail safe' thingy, you may end up dead in the water. It pays to pay attention.

newPTboater

I cut the BEC and ran the receiver off the battery pack..based on my test..I guess that was not the issue.. I ran the boat under load (in the bath tub) It ran for 3 minutes 15 seconds, then went into it's usual routine sputtered, quit momentarily, then the motors reversed direction. There was no sparks and both motors and ESCs were cool to the touch. I am open to any suggestions!

Here's what I have to work with 2 Mack Marine motors (12v) and gearsets, for batteries I have either 1- 12v gel cell (that was the original plan..had same results) 2- 7.2 NiMH packs (same results) 2- 12V Nimh packs (same results) 2 Pro Boat ESCs.

I still need to check the current draw of the motors..but if they check out OK..I guess I'm will to check out other ESC options..I'd like to get on with building my boat. Is their a set up you suggest with any of my battery/motor combos?

LtDoc

Just out of curiosity, what capacity are the battery packs, how many mAhs? I couldn't find it if you've said before.
I don't understand why that's happening, I'm missing something somewhere, just don't know what. If you are not changing the signal going to the receiver (adjusting the transmitter some way) The only reason I can think of is that the receiver is glitched in some way. If the ESC and motors are not getting hot then I'm doubting that either is getting over loaded. If it isn't the receiver then it would have to be the ESCs. Those are the only three things in the boat that could/would cause it. Have you tried talking to the manufacturor of the ESCs? Maybe they can shed some light on it.
I have an ESC that goes to full throttle if the transmitter is turned off before the receiver. That full throttle is in whatever direction the last received command was. It isn't the same ESC as yours though, and I really doubt if they are made alike. Beats me...
- 'Doc

newPTboater

The 7.2V pack is 3300 mAh and the 12V pack is 3700 mAH, the 12V gel cell is 7 AH.
The motors have a label that says 12V, 5 amp.
Since my last post, I have tried running each motor directly from the battery.
They ran fine with no heat and appeared to run at the same speed.
With some real ugly wiring and electrical tape, I have tried running the motors in parallel with one ESC.
I am cautiously optimistic, I got about 10 minutes of running without the mystery problems (I used 1 12V 3700mAh pack for the experiment)
If this proves to be reliable, I might stick with the set up(and do a real wiring job). What kind of run times do you think I would see with using the 12V 7Ah gel cell vs. the 12v 3700 mAH pack?

Mikie D.

Try disconnecting the Y harness and connecting each speed control to the receiver. If a 2 chanal radio use the steering channel, not needed in the tub. Then disconnect one of the BEC's, use the Y harness if you all ready cut it. This will give you a base line. If you can also use 1 battery.

Mike

LtDoc

Figuring a 5 amp draw from each motor, that would be a 10 amp total draw. That would mean something on the order of about 20 minutes with the 3700 mAH battery, and something like 40 minutes from the 7 Ah battery. Of course, that's +/- a couple of minutes each. And since you really don't know what each motor actually draws, I wouldn't put a whole lot of faith in those figures. No matter how long it's been, when things start slowing down, sort of, I'd head for the shore.
Would still like to know what's causing the problem. If you ever find out I hope you let us know.
- 'Doc

PS - Just did the 'number's for that 10 minute running time. It shows about 10 amps per motor, which sounds a bit closer to 'normal' current draw. (I've no idea, what's the max current draw for the ESCs?) So, for that amount of current per motor, cut the above times in half. That still doesn't account for the stopping and starting thingy, though.

Kaymac

I don't know if this will help or not but I experienced similiar problems with my twin pittmans using individual ESC's. After modifying the motors with capacitors, voltage spike suppressors and isolated grounding, the problem persisted. I then did a full process of elimination and found the culprit to be a third ESC that controlled my bow thruster. It was located too close to the main ESC's and whn I unplugged the receiver cord on the bow thruster, the problem stopped. I am now in the process of relocating the suspect ESC to a more distant location. This suggests some form of EMI was the issue as it would cause one of the drive motors to behave eratically and then stall completely.
Keith.

godeatsdog

I think Kaymac may have the answer you are after.

I read somewhere that running Twin ESC's off separate batteries can cause problems because of the lack of a common ground. It causes electrical interference and produces unexpected behavior. Linking the ground from the batteries would create a common ground and hopefully resolve the issue.

Best regards Chris

Kaymac

After working my boat for a week after making the changes, the glitching has been eliminated.
I'll post a couple of pictures to show the original layout as it was when the glitching occurred.

I placed the bow thruster Vantec ESC directly under the two Electronize units.
My wiring and component layout is placed on four levels. Motors, pumps and batteries all sit on the bottom (this is now where the Vantec ESC sits on a box to lift it out of harms way if water gets in and the bilge pump doesn't start quickly). The second deck is shown here with ESC's and junction bars. The third deck has my power distribution box, smoke unit, engine sound board and speaker, RF receiver and MCD 8 switch. The top level has three light circuits, radar head, horn audio board and speaker. All are working just fine after this issue was found and dealt with.

The only issue that continues is that the Vantec ESC does not work equally in both directions. I can trim the channel on my transmitter but it is still way off to one side. Does anyone have an idea of what may cause this or a quick fix? There is no adjustment on the ESC itself.

The third picture (a little fuzzy) is for those who suggest we scare the wildlife...one of these ducks nipped at my bumper tires while underway. They really couldn't care less if we are on their water on not!
Regards,
Keith.