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>> Home > Forum > Electrical Related > ESC POWER
ESC POWER
(463 views)
Author Message
RHBaker
(Fleet Admiral!)





Forum Posts: 87
4th Aug 2017 21:56  
>> Permalink
mdlbt.com/31693

The accepted wisdom is that only one power source should be used to power a receiver from an ESC. I can see where using a separate battery and a BEC would be questionable, but what about using two BEC connectors when using two identical ESCs?
The reason for my question is I am powering the Rx off the port motor ESC through its BEC in one of my models. The starboard ESC has the positive BEC wire disconnected.
The port ESC failed "ON" today causing my model to go in uncontrollable circles as the failure caused the Rx to shut the starboard ECS down.
If both ESC / BECs had been connected could I have retained control of the starboard motor as that ESC was fine?

RNinMunich
(Fleet Admiral!)





Forum Posts: 1027
4th Aug 2017 23:31  
>> Permalink
mdlbt.com/31695

Only if you put a blocking diode (rated for the BEC max current) in the positive (red) BEC lines to stop the BECs feeding back into each other. Otherwise you may damage one or both of the ESCs.
Not quite sure how the RX would react but I think it would be OK (may depend on the manufacturer /type) and you would have the double current capacity available for servos and functions. Test it on the bench first !!

Generally speaking you are right, and this is a problem I might be facing shortly with my twin screw destroyer Hotspur and quad screw cruiser Belfast! The more elegant way of course is to fit a Fail Safe switch which connects either the other ESC supply or a separate battery if the primary source fails. Such switch modules are available (at least here in Germany!) for a few quid. Cheaper than a damaged or wrecked boat!
BTW: was the RX still doing anything? Rudder control?
Not quite sure why the stbd ESC shut down if the fault was in the port unit!
Cheers Doug 😎
PS That's one of the reasons I prefer a separate RX batt when space and weight allow!


"Retirement is when you stop living at work -
and start working at living!" i.e. boat modelling!" 舰队的海军上将 😉 Doug
Dave M
(Fleet Admiral!)





Forum Posts: 1351
5th Aug 2017 10:31  
>> Permalink
mdlbt.com/31705

Hi RHBaker
What kind of ESCs are you using?
Doug
I would not use both BEC units even with your diode in place. Most manufacturers advise disconnecting one positive lead completely. Also if the ESC has a switch both ESCs must be switched on as I have damaged one of mine because it was switched off but still appeared to work. Result was similar to RH Bakers problem. I suspect the Mosfet gate voltage was exceeded without the internal power to the ESC, causing it to go permanently on. I also believe this may have been developed over time as I am sure this instance was not the first. The ESC still worked OK in reverse but went full on as soon as the stick on the tx was put forward. Further checking also revealed the internal BEC was dead. Sealed unit so no chance to repair.
Both
As Doug says a separate power supply is a better option if you have room, and modern switched mode supplies are freely available and will deliver much greater power for all your servos, lights etc
Dave


Live long and prosper

Dave
RNinMunich
(Fleet Admiral!)





Forum Posts: 1027
5th Aug 2017 10:39  
>> Permalink
mdlbt.com/31707

Hi Dave, I heartily agree. Why tempt fate? I have just bought a dual ESC form Hobby King to test with my destroyer.
Otherwise the only advantage I can see in having 2 ESCs is if you want to use tank type control (2 sticks) to give power assisted steering! (Or mix with the rudder control?)
If redundancy is the objective then a separate RX supply with NO BECs connected is the best bet.
Happy sailing all, cheers Doug 😎


"Retirement is when you stop living at work -
and start working at living!" i.e. boat modelling!" 舰队的海军上将 😉 Doug
Dave M
(Fleet Admiral!)





Forum Posts: 1351
5th Aug 2017 10:54  
>> Permalink
mdlbt.com/31709

Hi Doug my Olympic and Bills Titanic have three ESCs. The centre motor enables warp speed and produces a correct bow wave albeit at a very unscale speed. On such large models it helps to turn in a reasonable radius. My HMS Grenville also has two escs to help with manouvers. Then again I used to fly planes so still enjoy using all four sticks on my tx.
Dave


Live long and prosper

Dave
rolfman2000
(Admiral)





Forum Posts: 101
5th Aug 2017 11:45  
>> Permalink
mdlbt.com/31713

An easy answer is to just cut the red wire on on esc and insulate the end bbefore plugging into the receiver. Then you'll be powering off one esc only. Problem solved. Its the solution we use on all the quadcopters we fly. Hope that helps. Best wishes, Dave W 😊

RNinMunich
(Fleet Admiral!)





Forum Posts: 1027
5th Aug 2017 11:48  
>> Permalink
mdlbt.com/31714

Hi Dave, sounds good to me 👍
I'm going to try the 'tank' method on my Graf Spee, ca 5ft, twin screw or my destroyer. No Warp engines though (ran out of dilithium crystals!) 🤔
Belfast, 4ft plus, has 4 screws so offers more scope! Outers for cruising and 'power steering', inners to surprise the ATR 'sport' boats!!??
Now looking for some miniature ESCs (5 to 10A) for my multi-screw plastic magics, ranging from 30 to 90 cm and all long and thin! Typical naval ship form. Will probably end up with Viper Micros and Micron radio for the smaller ones.
Hope the rain holds off for you, sunny and warm 28°C here so on with the sanding 😡 and sealing! Cheers Doug 😎


"Retirement is when you stop living at work -
and start working at living!" i.e. boat modelling!" 舰队的海军上将 😉 Doug
RNinMunich
(Fleet Admiral!)





Forum Posts: 1027
5th Aug 2017 11:52  
>> Permalink
mdlbt.com/31715

Hi Rolf, Yep, standard recommended practise, but doesn't solve RH's loss of control problem! Cheers Doug 😎


"Retirement is when you stop living at work -
and start working at living!" i.e. boat modelling!" 舰队的海军上将 😉 Doug
Trillium
(Commander)





Forum Posts: 65
5th Aug 2017 12:06  
>> Permalink
mdlbt.com/31716

Regarding Doug's suggestion of putting a diode in the red wire from two ESC's, the forward voltage drop in the diode will reduce the voltage at the receiver by 0.6 volt less than the BEC puts out. Is this going to affect the operation of the receiver and everything connected to it? Does the BEC voltage vary depending on the load on the ESC, or is it stable enough?
Roy

Dave M
(Fleet Admiral!)





Forum Posts: 1351
5th Aug 2017 12:23  
>> Permalink
mdlbt.com/31718

Hi rolfman
Your quadcopters use forward only escs. I suspect the problem with model boat escs is the reverse. I don't have the circuit diagrams for ESCs so its difficult to be certain what causes the problem. I do know some escs with bec and switches work without being switched on if connected to a signal and power supply but subsequently fail usually with the full forward either on or off. Not all escs exhibit this which is why I asked what esc was being used.
Trillium
You are correct and is another reason I advised against this suggestion.
dave


Live long and prosper

Dave
rolfman2000
(Admiral)





Forum Posts: 101
5th Aug 2017 12:25  
>> Permalink
mdlbt.com/31719

Oh, sorry, i misread the original post. Even if both bec's had been connected, i dont think the situation would be any different. With one esc failing, i have noticed that its a crapshoot, as to what happens next, as i have had times when one has caused the other to fail, and also where the working one has continued at the same speed it was going (but in circles). The other option is to use a desperate battery for the 3rd, and disconnect bother the reds on the esc's. I reckon RHBakers occurrence was one of pure chance personally, as I cannot think of a logical reason for it happening. Best wishes Dave W 😊

RNinMunich
(Fleet Admiral!)





Forum Posts: 1027
5th Aug 2017 12:30  
>> Permalink
mdlbt.com/31720

Hi Rolf, I agree 👍
Personally I don't trust BECs anyway. Never did like anything with all eggs in one basket and no fail-safe!
Cheers Doug 😎


"Retirement is when you stop living at work -
and start working at living!" i.e. boat modelling!" 舰队的海军上将 😉 Doug
RNinMunich
(Fleet Admiral!)





Forum Posts: 1027
5th Aug 2017 15:41  
>> Permalink
mdlbt.com/31724

Hi All, Diodes: - Trillium is correct of course, although some ESCs have a 6V BEC. Some RXs work off 3 - 3.7V for 1S LiPo operation in small boats. Not the case here. 😉
As for stability I would guess that you get what you pay for! Cheap unstable, expensive stable!? Higher current versions with a switched supply?
But the diodes are the only way to achieve the situation posed in the original question. Personally I wouldn't do it for all the reasons listed above.
In RHs case seems to me the port ESC fault shot the BEC and robbed the RX of it's power supply resulting in total loss of control.😡 That's what shut down the stbd motor (ESC went Fail Safe) and why I asked if the rudder still responded; "No answer came the stern reply" 🤔
Why it may have failed Dave-M knows better than I, more practice! 👍
Cheers Doug 😎


"Retirement is when you stop living at work -
and start working at living!" i.e. boat modelling!" 舰队的海军上将 😉 Doug
RHBaker
(Fleet Admiral!)





Forum Posts: 87
5th Aug 2017 22:11  
>> Permalink
mdlbt.com/31734

First, thanks to all for their helpful replies. To answer a few questions:

1) The installation has two independently controlled ESC/Power train systems in a long, narrow patrol boat. They were fitted for maneuverability and achieve that target well.

2) All Rx functions failed when the ESC failed, pointing to a BEC circuit failure.

3) The ESCs are of UK manufacture and, I hasten to add, have previously worked well. Have used this product for years and am satisfied with it.

4) The presumed reason for failure was, in a effort to increase the performance and reduce the weight of the model the power has (after a series of trials with 9 to 14 v NiMh batteries) gradually evolved to a 17 volt Li-Po system. This final iteration had performed well for some time.

Guess using a 12 volt ESC on a 17 volt system would eventually lead to failure - Mea Culpa!
Funnily enough,when cooled down all functions work properly - until they heat up again.
Have ordered 2 more ESCs from the same manufacturer, but now rated at 12 - 24 volts - should solve the issue.

In view of the various recommendations to use a separate Rx power system, think this is the easiest solution to avoid a total system failure in future.
Again, thanks for the advice.

RNinMunich
(Fleet Admiral!)





Forum Posts: 1027
5th Aug 2017 22:31  
>> Permalink
mdlbt.com/31735

Oh yeh! Every picture tells a story! Had we known that at the beginning we would have missed out on an interesting debate 😉
Looks like you triggered the ESC's thermal cut-out. Lucky it wasn't permanently damaged.
MIL Standard 217 Handbook for calculating MTBF (Mean Time Between Failure) lists the two top Stress Factors as Environment - Over-temperature and Exceeding rated Voltage - Over-volts. 🤔 After that comes Component Count - the more parts the more likely it is that one will go PHUT when you need it 😡
During my recently ended career I had a lot to do with MTBF for naval ship systems, and the associated FMECA - Failure Mode Effect And Cause Analysis!
Lesson learned!? We all learn from our mistakes and those of others - I hope😉
Have fun with the new ESCs.👍 Don't get any speeding tickets 😉
Cheers Doug 😎
PS having a second power supply in the system more than doubles the MTBF.
BTW: Where do you buy your 4.6 cell LiPos !?😲


"Retirement is when you stop living at work -
and start working at living!" i.e. boat modelling!" 舰队的海军上将 😉 Doug
Dave M
(Fleet Admiral!)





Forum Posts: 1351
6th Aug 2017 09:43  
>> Permalink
mdlbt.com/31736

Glad to hear you have solved your problem. Overrunning any system will result in some interesting issues and you are fortunate that yours shut down or failed open circuit otherwise all the electronics could have cooked.
If you are getting a separate on-board power source the best option is to go for a switched mode supply, most will give you lots of amps without the heat problems of an ESC and are designed to work with higher battery voltages.
You must disconnect any +ve power lead from any ESC to your rx. If your ESC has an on/off switch do make sure it is switched on, preferable before you power up the switched mode unit.
Be good to see some pics or on water video
Dave


Live long and prosper

Dave
RHBaker
(Fleet Admiral!)





Forum Posts: 87
7th Aug 2017 02:30  
>> Permalink
mdlbt.com/31757

Hi Dave,
The vessel in question was my Damen 4207, which has featured in an earlier blog. The installation of the LI-PO battery transformed the model, which now floats above the waterline and performs well.
I am still trying to get a video and, once the new ESCs are fitted, will try again.In the meantime here is a picture of her underway.


Attached Files - Click To View Large

Dave M
(Fleet Admiral!)





Forum Posts: 1351
7th Aug 2017 09:41  
>> Permalink
mdlbt.com/31760

Very impressive. I look forward to seeing the video when available.
Thinking about my last post I may have given the wrong advice about the switch on sequence. Some ESCs set the neutral point at switch on and some 2.4Ghz rxs take a few secs to power up resulting in the ESC not finding a signal. So if you have such a system I would switch on the rx power source first and wait for the rx light to show solid before switching on or applying power to the ESCs.
Dave


Live long and prosper

Dave