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Old Nov 22, 2011, 10:25 AM
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Farnham Common, UK
Joined Oct 2009
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Help!
Seaking 60 amp ESC overload?

I have installed a 2881KV brushless motor with a Seaking 60 ESC, a 35mm diameter 30 degree pitch prop and an 8.4V NiMH battery in my Dumas Chris Craft 19" racer. Goes like the wind but sometimes stops in mid lake for no apparent reason My supplier says that this prop size is too big for my motor/ESC combination and that it is cutting out on overload. He recommends a smaller prop and a lower voltage (7.2V) NiMh battery. The set-up is water cooled and, as far as I can tell, does not even get warm. I also have yet to apply full throttle. I use the same power set-up in my Bluebird K7 driving a larger 36mm diameter 50 degree pitch prop with no problem. This boat, or course, planes over the water whereas the Chris Craft goes through it with therefore presumably with more resistance.

My total ignorance of these matters will be apparent from the above and I would very much appreciate any suggestions or advice. Photos of both boats below.

Jeremy
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Old Nov 22, 2011, 10:53 AM
I feel the need for speed!
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Is the 2881kv motor a 380 size? If so is it an L or XL etc......... Seems like quite a high kv for that boat, i would have gone witb a motor in the 1500-1800kv range and then volted it accordingly.
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Old Nov 22, 2011, 11:27 AM
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It's said to be a replacement for 380 to 550 but much more powerful! It fits a 360/400 mounting bracket. I don't know about L, XL etc. Thanks for your suggestion. I could change the motor but would prefer to stay with a 7.2V or 8.4V NiMh battery (I prefer not to use Lipos).
Jeremy
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Old Nov 22, 2011, 12:43 PM
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Sneek, Netherlands.
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Quote:
Originally Posted by JeremyBB View Post
I also have yet to apply full throttle.
Jeremy
Hi Jeremy,

That remark caught my eye...

'Cheap' ESC's don't like running in partial throttle, they get hot, regardless of the watercooling; if you have been running partial throttle for most of the time, most likely the ESC overheats (probably the motor too, but that won't stop it from running until the smoke comes out...) and shuts down thermally to avoid damage to it.

I'd suggest to try a smaller prop and run 80% full throttle, see how far you get with that.

Regards, Jan.
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Old Nov 22, 2011, 12:47 PM
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Well 8.4V is about S if you talk Lipo's. I ran a 2200KV motor with 3S (11.1V) using a 38mm prop and does not have any problems. And this is with only a 35amp esc...
What Jan said makes sense, I'm always at full throttle so that is maybe why I don't get a problem.
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Old Nov 22, 2011, 06:03 PM
I feel the need for speed!
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Originally Posted by pompebled View Post
Hi Jeremy,

That remark caught my eye...

'Cheap' ESC's don't like running in partial throttle, they get hot, regardless of the watercooling; if you have been running partial throttle for most of the time, most likely the ESC overheats (probably the motor too, but that won't stop it from running until the smoke comes out...) and shuts down thermally to avoid damage to it.

I'd suggest to try a smaller prop and run 80% full throttle, see how far you get with that.

Regards, Jan.
The 'part throttle' issue was why i was referring to using a lower kv motor, the boat looks like more of a cruiser than an FE racer, so why use a "hot" motor at nearly 2900kv, forcing the use of a tiny prop. I still think a motor like this with a bit larger prop would be best.

http://www.hobbyking.com/hobbyking/s..._Inrunner.html
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Old Nov 22, 2011, 06:37 PM
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The issue you describe sounds like what happens when the ESC hits LVC. Try running it on "no protection" if you haven't already. Otherwise the ESC is trying to protect a LiPo that isn't powering it.

If the ESC still has the default settings, than your issue lies there.
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Old Nov 22, 2011, 08:50 PM
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A big difference between the two boats is that the chris craft runs a fully submerged prop, where as the bluebird is a surface drive. That makes a huge difference in how much load a given prop places on the motor.
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Old Nov 22, 2011, 08:52 PM
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Originally Posted by wparsons View Post
A big difference between the two boats is that the chris craft runs a fully submerged prop, where as the bluebird is a surface drive. That makes a huge difference in how much load a given prop places on the motor.
and a 25,000 rpm prop at that..............

The whole key to FE boats is to find a setup that you can run at full throttle comfortably.................its a balancing act, but if you find that you have to run half throttle for it to run properly/safely, then you should cut the kv darn near in half.
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Old Nov 23, 2011, 04:44 AM
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Thanks to all for your helpful advice.

Losiefiend - No protection is selected

Jan - it's strange that a brushless motor/ESC heats up less as more throttle is applied - Isn't the reverse is true with brushed units?

Scorpion - I will try a lower kV motor, but don't I need water cooling? I would ideally like a motor of much the same physical size as the current one (32mm diameter, 45mm long) fitting the same 380/400 motor mounting bracket.

It looks like horses for courses. I will transfer the hot motor to my Slo-mo-shun which could do with upgrading from its Graupner Spped 600 Rave 7.2V unit and get something more sedate for the Chris Craft.

Jeremy
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Old Nov 23, 2011, 02:55 PM
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Quote:
Originally Posted by JeremyBB View Post
Jan - it's strange that a brushless motor/ESC heats up less as more throttle is applied - Isn't the reverse is true with brushed units? Jeremy
Hi Jeremy,

Only partially; if you run a surface driven boat at half throttle and the boat doesn't plane (planing means only one (prop)blade in the water) you're overloading the (brushed) motor, as the entire prop is under water.

If it's a subsurface drive and the components are compatible (Scorp's balancing act), you can run a complete battery charge while crawling along at one quarter throttle, nothing will overheat in a brushed set-up.

Regards, Jan.
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Old Nov 24, 2011, 02:45 AM
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Hi Jeremy.
All good advice from the guys on the lower kv motor for that boat. You'll find it will work better for you.
I run around 1000kv motors on 4s or around 1500kv motors on 3s in my fast scale boats & get good realistic speeds.
Also, I believe that the cutout issue is definitely an LVC issue. The voltage curve of your NiMh packs will sag a lot under that load. The ESC has LVC for NiMh packs if you read the manual. Even if you don't set any values there is a default setting already programmed in. Here's the section of the manual I'm referring to...... It may apply. The default setting is 2.8V/cell.

Protection Function
1. Low voltage cut-off protection: If the voltage of a lithium battery pack is lower than the threshold for 2 seconds,
the ESC will cut of the output power. Please note that the ESC cannot be restarted if the voltage of each lithium
cell is lower than 3.5V.
For NiMH/NiCd battery packs, if the voltage of the whole NiMh/NiCd battery pack is higher than 9.0V but lower
than 12V, it will be considered as a 3 cells lithium battery pack; If it is lower than 9.0V, it will be considered as a 2
cells lithium battery pack. For example, if the NiMH battery pack is 8.0V, and the threshold is set to 2.6V/Cell, so
it will be considered as a 2 cells lithium battery pack, and the low-voltage cut-off threshold for this NiMH battery
pack is 2.6*2=5.2V.
2. Over-heat protection: When the temperature of the ESC is over a special value for 5 seconds, the ESC will
gradually cut off the output power.
3. Throttle signal loss protection: The ESC will cut off the output power if the throttle signal is lost for 0.2 second.

Cheers.
Paul.
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Old Nov 24, 2011, 05:18 AM
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Farnham Common, UK
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Hi Paul

Thanks for the advice. I will transfer the existing motor to my Slo-mo-shun and get a lower KV unit for the Chris Craft. Do you use watercooling for the ESC/motor is your fast scale boats? Some say it's needed, some say it isn't. The Seaking 60 ESC is watercooled so I should probably fit a water jacket to any new motor.

I don't think LVC is an issue in this case. I've had no problems with Bluebird which is at full throttle the whole time. Also, I don't recognise the instructions you quote. Those I have for the Seaking seem to suggest that the 'no protection' setting. means no protection.
http://www.hobbywing.com/upload/manu...g_080628_e.pdf
Are we looking at the same unit?

Cheers

Jeremy
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Old Nov 24, 2011, 07:16 AM
I feel the need for speed!
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Here's a neat little motor with an impeller....................may not even need watercooling

http://www.hobbyking.com/hobbyking/s...er_1500kv.html
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Old Nov 24, 2011, 12:20 PM
RELAX. You'll live longer
785boats's Avatar
Brisbane- Australia
Joined Jul 2007
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Yep. Same unit Jeremy.
In the link you posted it is on page 2, item #3. But if you have manually set it to no protection you are right, it shouldn't be the issue. The only other reason I can think of for your ESC cutting out is that maybe the BEC is faulty. I have seen the same issue in a Turnigy 180A which is the same series of ESC's as the Hobbywing ones.
I always cool the motor & ESC in the fast scale boats too. It's cheap insurance.

Scorp.
I've often looked at that series of motors. There's some nice motors there for scale boats.
All the best.
Paul.
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