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Need opinions on what could be wrong

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Old 12-12-2011, 08:48 PM
  #1  
wetsleeves
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Default Need opinions on what could be wrong

I have a cat running twin leopard brushless motors, 2 swordfish 240 HV esc
running 10s lipo's in parrallel.
The 2 Swordfish 240 ESC seem to be going into lvc, even though the packs are 100% charged.
The boat would run for about 3 seconds then slow down to a stop. Release the
trigger, pull again and it would run again for another 3 seconds and do the
same thing.
I had the LVC set to 10s and soft cut out at 3.3v. I decided to set the LVC
to auto and see if that would fix the problem but still the same thing.
Packs are 2 fully charged 10s 5000 mah hooked up as a 10s 2p setup. Packs
are thunderpower 30c 5000mah.
Boat ran good when I first bought the esc early on in the year, then i didnt
use the boat for a few months , now this.
Motors, esc's and batteries all cool.
I changed the receiver and y cable to make sure that that wasnt the problem, changed the receiver battery,
but I'm still getting the same result.
I read on the swordfish site that the esc would go into auto shut down if there was a signal lost or
interference. I thought maybe the servo might have been interfering with the reciever so I diconnected it but still the same thing
Im using a futaba fasst 2.4 ghz radio set on HRS mode.
Any ideas would be apreciated.

Peter
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Old 12-12-2011, 10:07 PM
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Dan S
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Default RE: Need opinions on what could be wrong

ummm
so you are using a separate pack for the receiver! correct?
what size is the pack?

are you using all digital servos?
HRS mode only if all servos are digital, if not PPM mode.

don't think it will solve the problem, but lets start somewhere.
did you put your Lipos into storage charge during those few months or full charge?
when packs are at 100%, did you do a load test on them to see how much they are dropping?

Dan.
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Old 12-12-2011, 10:42 PM
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Default RE: Need opinions on what could be wrong

Im using a 6v receiver pack and the servo is digital.
The packs were stored at 3.8v per cell.
What would be the best way to do a load test on the packs?
I ran the boat on the week end for about a minute with this issue and the packs were sitting at 4.05v per cell.
I only ever ran the boat for about 3 minutes ( when boat was running fine) and when Id bring the boat in pack are around 3.8v per cell.
Even when just pulling the trigger the motors only run for about 3-5 seconds then slow down and then stop with no load on the motors.
The thing is when you pull the trigger the boat takes off and flies for about 3 seconds then slows down, relaease the trigger and pull it again same thing. Takes off then slows down.

Peter
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Old 12-12-2011, 11:27 PM
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Default RE: Need opinions on what could be wrong

I agree that this sounds like a LVC problem.
Try decreasing your LVC treshold voltage.
The voltage does drop significantly when pulling big currents.
I got a T-180A, Leopard 3674 2200Kv and 6s 4400mAH setup, and it does go into LVC even on fully charged packs, when LVC was at its stock treshold voltage (3.0 V i believe), so I disabled LVC altogether.
That fixed it for me.
If you don't want to disable LVC alltogether, try just decreasing the treshold voltage.
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Old 12-12-2011, 11:28 PM
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Default RE: Need opinions on what could be wrong

do you need to reprogram the escs??
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Old 12-12-2011, 11:57 PM
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wetsleeves
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Default RE: Need opinions on what could be wrong

I set the LVC to auto instead of 10s and I did reproggramme the esc to cut the voltage off at 2.5v ( which was the lowest setting on the programme) and I still got the same result.
I wanted to disable the LVC but you cant on the swordfish.
I do run the esc in parallel with the batteries. I will try and run each esc seperatly to each batteries and see if there is any change.
Im not sure if it might be a soft ware issue with the esc's.
I emailed Hifei to ask them what they thought but no reply as of yet.
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Old 12-13-2011, 12:02 AM
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Default RE: Need opinions on what could be wrong

ok, well let us know, cuz now I'm curious...
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Old 12-13-2011, 12:10 AM
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Default RE: Need opinions on what could be wrong

I will, its got me stumped how both esc are doing the same thing at the same time.
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Old 12-13-2011, 12:13 AM
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Default RE: Need opinions on what could be wrong

I don't know this particular ESC, but I do believe that auto LVC simply detects your cell count automatically, and will not have any impact on cutoff treshold.
Can you post a sketch of your wiring harness?
If you got your wiring put up in such a way so that the two ESCs can work as a voltage divider for each other, then the LVC will trigger once you get just a slight differential load on the motors.
Do you have a wattmeter? It would be very helpful, to get some recordings on max amp draw and minimum battery voltage under load.

The fact that both ESCs is doing the same thing might indicate that the ESCs are not at fault, and the problem lies within the configuration. Either of the ESCs them self, or some other part of the drivetrain.
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Old 12-13-2011, 12:38 AM
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wetsleeves
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Default RE: Need opinions on what could be wrong

Here is a pic of how the esc are connected at the moment. I will connect each esc to its own lipo tomorrow and see if that changes anything.
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Old 12-13-2011, 01:44 AM
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Default RE: Need opinions on what could be wrong

I assume those big slabs of sgrink wrap is solderpoints that joins all 4 of the wires entering them?
In that case, any differential voltage to the ESCs will be impossible.
How much amps are you drawing, how long is your battery wires, and what wire gauge?
What kind of plugs are you using?
I think they appear quite small to be used on a high current setup. You might have a significant voltage drop over your plugs, contributing to the LVC.
Are the plugs warm to the touch immediately after you run the boat (assuming you ever got it to run for extended period with a gentle throttle finger)?
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Old 12-13-2011, 02:04 AM
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Default RE: Need opinions on what could be wrong

The plugs are 8mm gold connectors on the esc. The batteries have 6mm gold connectors.
The boat ran well before I put it away for the 2 months that I didnt use it. When the boat was running after 21/2 to 3 minutes of run time the motors, batteries and esc were cool to touch.
Plugs were cool also.
Here is a link to the esc's
http://www.hifei.com/en/News_View.asp?NewsID=107
And here is a link to the boat running, when everything was ok. Sorry about the quallity but my 6 yaer old was filming it.
http://www.youtube.com/watch?v=RdtYtmtiuKU
I ran the boat a few more weeks after this video was made and all was ok until I put it away for 2 months..
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Old 12-13-2011, 02:10 AM
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Default RE: Need opinions on what could be wrong

I ran the boat at home today on the bench just trying different things and only just squeezing the throttle it would only run for a short period of time before the motors would slow down to a stop. So the amp draw would only be minimal compared to when you pull the trigger hard.
I will need to get myself a data logger in the future.
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Old 12-13-2011, 08:07 AM
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Default RE: Need opinions on what could be wrong

8mm plugs on the ESC, and 6mm plugs on the batteries?
Does that mean that there is 8mm plugs between motor and ESC, and 6mm between battery and ESC?
The amp draw per wire is higher on the battery side, than it is on the motor side.
Meaning you should use the biggest plugs on the battery, not on the motor.
Just mentioning though, thats not relevant for this cutoff issue.

Datalogger would be helpful, or at least a wattmeter, to see what's going on.
Are you sure your batteries is in good condition and fully charged?
I think its not a problem with the ESCs since both behave the same way, and have worked well before.
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Old 12-13-2011, 10:42 AM
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Default RE: Need opinions on what could be wrong

I did not read if you cycled your batteries.  Discharging them and then recharging may bring them back to life.  I'm new to LiPos but that was always something that worked with NiCds.
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Old 12-13-2011, 11:08 AM
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Default RE: Need opinions on what could be wrong

If they have been stored for a long time it might be a good idea to at least recharge them, even if they were fully charged when put away for storage.
LiPo cells have relatively high self discharge rates.
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Old 12-13-2011, 01:02 PM
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Default RE: Need opinions on what could be wrong

Von the batteries were stored for 2 months at 3.8v a cell. They were charged up to 4.2v per cell and ballanced within 0.010. I cant see it being the packs as if I only pull the trigger slightly, the motors run for a short time then slows down.
I will reconnect the esc seperatly and to their own pack and see if that makes a difference as soon as I get a chance.
Now I need to go to work and earn some money.
Thanks to everyone who has replied.

Peter
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Old 12-13-2011, 01:08 PM
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Default RE: Need opinions on what could be wrong



Hello, just a thought but have you changed the transmitter settings at all?(Perhaps used the transmitter on another boat or car etc?)

If you have a servo tester try plugging the ESC in to that and advancing that- just eliminates a component.

Good luck and be sure to post what the problem was when you find it!

Cheers
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Old 12-13-2011, 04:01 PM
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ORIGINAL: Goldenduff



Hello, just a thought but have you changed the transmitter settings at all? (Perhaps used the transmitter on another boat or car etc?)

If you have a servo tester try plugging the ESC in to that and advancing that- just eliminates a component.

Good luck and be sure to post what the problem was when you find it!

Cheers
I second trying a fresh model on your radio. It sounds like you have eliminated everything else.
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Old 12-13-2011, 04:07 PM
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Default RE: Need opinions on what could be wrong

I am a plane guy but have had similar problems with esc’s
First off, is anything binding the motor/driveshaft/ect, this could cause the motors run out of phase (aka not run at all, just sit there and jitter)
Second make sure your throttle trim is down all the way
Third make sure your esc is “thinking” you have 10 cells (beeps ten times?), if it thinks you have 12+ cells that could explain the low voltage cutoff
Forth if you throttle slowly does it last longer? Maybe a few cells are bad (can’t hold high current)? Put the battery in another esc and try it?

if i had to guess your esc is assumeing you have more cells than you do, or you have a bad cell(s) which triggers the low voltage cutoff
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Old 12-13-2011, 08:21 PM
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Default RE: Need opinions on what could be wrong

LiPo cells have relatively high self discharge rates.
Not. Lipos have a very low self-discharge rate, it's one of their big features.

They don't benefit from cycling, but in this case cycling your lipos would tell you about the battery condition. I agree on the ESC possibly detecting a wrong cell count, rare but not unheard of. What are you using for wattmeter? 
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Old 12-13-2011, 08:46 PM
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Default RE: Need opinions on what could be wrong

I dont have a wattmeter at the moment. I isolated each motor and esc and ran them seperatly, (one at a time) and both did the same thing. Only ran for a short period of time then slowed right down.
I tried both batteries on each esc with the same effect, so its got me beat.
I will go through all the soldered joints again and make sure there is no dry joint.
I disconnected the y harness and plugged the esc straight into the receiver, one at a time and it still didnt fix the problem.
I will recheck all the connections on more time and see if any thing is loose.
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Old 12-13-2011, 11:52 PM
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Default RE: Need opinions on what could be wrong

Hi, did you try using a servo tester?
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Old 12-14-2011, 01:38 AM
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Default RE: Need opinions on what could be wrong

No, I dont have a servo tester. The receiver work well in my gas boats so I dont think it would be the reciever.
I got a reply on another site from a fellow hobbiest and the same thing happened to him. His esc's went faulty and did the same thing. He sent them back and they repaired them for him. I spoke to Michelle from hifei who told me to send the esc back to them and they will check them out for me.
I will send them back tomorrow if I get a chance.

Peter
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Old 12-14-2011, 03:13 AM
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Default RE: Need opinions on what could be wrong

That is good of them to check the ESCs.

IF you haven't already sent them do you have a different transmitter and receiver you could use? Or a spare model memory where you could start from scratch? Just a thought as most of my plane motor problems have been from digital and anolog trim taps, servo reverse etc
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