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Old May 13, 2006, 12:27 AM
Next time I'll ARTF...
glydr's Avatar
Canberra, Australia (Southside)
Joined Feb 2004
4,634 Posts
Question
Why does my BM2408-1 surge at full throttle?

Hi all,

BM2408-1 brushless with GWS EP8043 surges at full throttle.

At first I thought it was a power thing, but I'm starting to wonder if the prop isn't rigid enough and deforms, causing the surging.

What do you think?

glydr
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Old May 13, 2006, 02:14 AM
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AeroNut45's Avatar
Australia, VIC, Keysborough
Joined Jun 2004
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Didn't you get a 8x4 HD prop? What ESC are you running?
Could be the ESC!
Knut
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Old May 13, 2006, 04:07 AM
Next time I'll ARTF...
glydr's Avatar
Canberra, Australia (Southside)
Joined Feb 2004
4,634 Posts
No HD's available at the moment but have a pack of EPs from Paul. It was good advice AN45, you havent been ignored.

I don't know about the esc - was supplied with motor with hydrofoam kit.
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Old May 13, 2006, 07:31 AM
Good Better Best quest.
olmod's Avatar
Australia, VIC, Cranbourne East
Joined Apr 2004
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Is your battery voltage holding up at wot?
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Old May 13, 2006, 08:54 AM
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AeroNut45's Avatar
Australia, VIC, Keysborough
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I think oldmod might have a point. I have some old lipolys, which sag under load and the ESC cuts in and out. So it would be worth while maybe run it on a bigger pack, to see if it does the same thing.
Knut
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Old Jun 15, 2006, 06:38 AM
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Kentucky's Avatar
Melbourne, Australia
Joined Apr 2004
608 Posts
My guess is it's your ESC.
The ones supplied with the Hydrofoam are Towerpro.
I have a 30A and 18A.

The 30A controller cutoff kicks in at 6.8V on 2S and reduces current.
The voltage never drops below this value, the motor doesn't cutout, just a gradual decrease in power and the motor surges slightly.

The 18A cutoff starts at 6.1V and surges wildly once this voltage is reached.
I know of others who have noted this also.

If you have an e-meter it can be clearly seen.
I guess you get what you pay for.
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Old Jun 15, 2006, 08:08 AM
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glydr's Avatar
Canberra, Australia (Southside)
Joined Feb 2004
4,634 Posts
Hi all,

I've found that it is a low power thing... full charge = no worries and as the pack gets to the end the surging starts. Must be the 18A.

Thanks for the feedback!
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Old Jun 15, 2006, 05:39 PM
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Melbourne, Australia
Joined Apr 2004
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This is true but it's the way the ESC behaves as the batt drops in voltage.
It's a simple feedback circuit ie: batt gets to LVC - current is reduced. Current is reduced - voltage increases. It gets itself into an endless loop and the revs go up and down.
Better ESC will either reduce power gradully or cutoff completely.
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Old Jun 15, 2006, 07:28 PM
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Australia
Joined Mar 2006
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Fact is you should not be running once this happens anyway! Running your battery down more than 80% or so of its total capacity is a bad idea if you want it to last a reasonable cycle life. None of this technology is fool proof, we are asking alot of these tiny 3 phase controllers, and of the batteries, you should get into the habit of landing before you hit LVC, relying on the ESC will definitely shorten your battery life regardless who makes the ESC.
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Old Jun 15, 2006, 07:37 PM
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Melbourne, Australia
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That's the whole point of the LVC to stop the batt going past a set limit.
3V per cell is concidered safe to perserve the life of the batteries.
Just set your LVC to a higher level (if you have a ESC that will let you) if you want to be conservative.
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Old Jun 15, 2006, 08:49 PM
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glydr's Avatar
Canberra, Australia (Southside)
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Great advice - I have certainly placed too much trust in this ESC with my most expensive flight pack! Thanks again all.
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