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Old 10-22-2012 | 07:21 PM
  #3039  
Sofa King
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From: In a VAN down by the RIVER
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Originally Posted by justpoet
Slightly off topic, but here's an ESC temp and performance question.
We recently decided to try a long race combining nitro and electric at a club race. It was going to be 20 minutes, but we decided just prior to make it only 15.

My electronics setup on the EB48 is a 5200mah/60c, Tekin T8 1900 w/18t, Castle MMP, Castle BEC for no-brand servo and rx.

I knew going into this that I would have to be easy on the throttle to attempt to make a 20 minute main, and even though it was now only 15 minutes, I went in with that mindset. So, I was generally conservative in getting on power and did more constant lower power instead of blips of power in portions of the track where I could. With about 7 or so minutes to go, just as the nitros were starting to pit, I noticed a lack of power. I couldn't get the punch to clear jumps I normally do, and had to alter my line. By the end of the race, I couldn't clear the 8th scale tripple anymore unless I had a run up to it (normally I can do it from about 2 and a half feet).

I figured the battery must've faded faster than I thought, or that I'd gotten some binding someplace during the run and gotten the motor way to hot. What I found though, was quite different. The motor came off at 130 and the battery at only 90...but the ESC was 170. I also took far less voltage out of the battery than I'd thought, as it was still at 7.84v.

The MMP is set to not do timing changes and generally fairly conservative (since everything was originally set up for all day practice runs...which I haven't had a chance to do yet...though I've had several runs of a full pack without much fading until the last 2 laps).

Any thoughts? Is this due to the change in driving style (which the EB48 really liked)? The esc fan was working and generally after a normal 6 or 8 minute run I'm at normal temperatures for the ESC and about 5-10 degrees warmer for the batt and motor.
Make sure you have the latest firmware on the MMP... I had some weird issues (suspect they were heat related) about the 7 min mark with a MMP and 2 MMM's... latest firmware appears to have fixed the issue.

Food for thought: Your change in driving style was likely the cause of higher ESC temp... ESC' work best (most efficient) at full throttle, when you limit use of full throttle, you cause higher ESC temp. This is why ESC makers will tell you to gear down or get lower kv motor rather than limit throttle endpoint. As an example: I had a 1/18 truck with brushless system and Nimh batts; it would run pack after pack doing speed runs, jumps, burnouts and generally just tearing it up outside, and the temps were always about 130, on motor, ESC and battery. If I ran it in the house, where I could not use much full throttle, my motor and battery temps were about 20 - 30 degrees lower and the ESC temp would rise 20 - 30 degrees.
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