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Old May 03, 2012, 03:24 PM
RES flyer
Portland, OR
Joined Feb 2009
7 Posts
Discussion
Brushless ESC with a brushed motor

I have an old Speed 480 sailplane that I originally flew on Nmih. It has an old Jeti brushed ESC. I want to switch to Lipos to save the weight. I plugged in a Lipo pack to the old ESC and it worked fine - until the next day when I went to charge the Lipo pack and discovered 2 dead cells. I have a new brushless ESC. I would rather use it now that than replace the old 480. Will the old 480 work with the brushless ESC if I just connect the + and - and leave the white lead from the ESC unconnected?
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Old May 03, 2012, 04:57 PM
Marion
USA, NC, Hillsborough
Joined Oct 2003
1,015 Posts
No. It doesn't work that way at all. Do not try it, please.
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Old May 03, 2012, 04:58 PM
Registered User
Staffs, UK
Joined Nov 2003
10,258 Posts
No. There is no + and - output from a brushless ESC,. All 3 wires do the same thing and it doesn't include driving a brushed motor....the way the ESC works is completely different.

Steve
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Old May 03, 2012, 05:00 PM
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Bruce Abbott's Avatar
Hastings, New Zealand
Joined Jan 2001
5,169 Posts
No, it won't work.

If you are worried that your Jeti might be over-discharging the Lipo, limit your motor run time to 2 or 3 minutes, then check that the battery hasn't gone below 11.1V. If your radio doesn't have a timer then just count off the seconds for each motor run (eg. 30 seconds x 4 runs = 2 minutes).
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Old May 03, 2012, 05:04 PM
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C₄H₁₀'s Avatar
United States, AK, Fairbanks
Joined Aug 2009
12,372 Posts
You could also get a brushed ESC with a lipo cutoff function. They're pretty inexpensive these days.
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Old May 03, 2012, 06:01 PM
RES flyer
Portland, OR
Joined Feb 2009
7 Posts
Thanks for the input folks! I think my brushed ESC may have killed my Lipo pack. I'll use my Nmih until I get the motor replaced.
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Old May 04, 2012, 02:25 AM
Registered User
Letchworth, Great Britain (UK)
Joined Jul 2004
11,435 Posts
Quote:
Originally Posted by soprano1 View Post
Thanks for the input folks! I think my brushed ESC may have killed my Lipo pack. I'll use my Nmih until I get the motor replaced.
You didn't leave the pack plugged in until you went to charge it next day, did you? That could drain any battery.

The older Jeti ESCs are programmed to shut down (lvc) when the battery voltage reaches 68% (I think) of what it was when the battery was plugged in. For a fully charged LiPo at 4.20v that'll be 2.86v for lvc, which is far too low. It's even worse if the battery wasn't fully charged when it was plugged in.

Other than that, there's nothing about the ESC that makes it unusable with a LiPo. If you want to use LiPo you simply need to time your flights so that you stop flying before 80% of the battery capacity has been used. In fact, that's true even for "LiPo friendly" ESCs, for lvc should only be regarded as a safety feature, not as your regular indicator to stop flying.
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Old May 05, 2012, 01:10 PM
RES flyer
Portland, OR
Joined Feb 2009
7 Posts
Thanks abenn. Very valuable info. I think I may have left the batteries plugged it
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