The ESC arrived, success!! ... then disaster!

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The ELF 100 ESC (electronic speed controller) arrived today and I installed it in my Piaggio Boxer. The install was a cinch and everything seemed to be going very smoothly.

I did some test runs with the rear wheel elevated using my 24V SLA batteries. Here is my data table:

DialMotorRear SpindleTire / SpeedAmp Draw
0-10 rpm0 rpm0 rpm0.03A
241116214 rpm / 1 mph -
3118033531 rpm / 2.5 mph -
418011495120 rpm / 10 mph6.6A
523901950156 rpm / 13 mph8.2A
628502330185 rpm / 15 mph9.4A
733272720217 rpm / 18 mph10.16

I ended the no-load test at dial position 7 on the servo tester as I didn't have a secure way of securing the moped on the center stand and if it came off the center stand during the test, the kinetic energy would rocket it off my back deck.

I tried some partial loads and the amps consumed quickly jumped to 30A as the ESC tried to maintain motor speed.

The motor sounded very good and heated up only a very small amount (to 38 centigrade). So everything looked good for a road test. I took it to my front yard and dialed the servo up to 4.

The moped took off and I dialed it to 5 and went down my street at about 15-20 mph. At the end of the street, there is a slight down incline and in order to come to a stop, I dialed the servo back to 0.

The rear wheel skidded to a halt and the ESC beeped menacingly at me then shut up. I tried to dial speed back up again and nothing happened.

I tried resetting the system and it didn't work. That's when I noticed the ESC was getting VERY HOT. I now have a blister on my index finger. I yanked my main system power and pushed the unit back home. I'm just glad it chose to blow near my house and not 5 miles out!

I let the ESC cool down and then plugged it back in again. It quickly started heating up again, drawing 10 A off the battery (240 watts) and not making any sounds (it normally will "sing" to you to let you know it's OK).

Although I didn't see where it went, I have the feeling that I let the magic smoke out of my $30 ebay special ESC. I've since yanked it off the bike and will likely go and buy a "real" ESC (like a Phoenix HV100).

Until then, I'll try to conduct an autopsy on my ESC. I've got the protective shrink wrap off and the chip that seems to be the one getting super hot is marked 78M05 and it has three leads coming off of it. I'm hoping that if I post some good autopsy pix, maybe Fechter on E-S can help me diagnose it.

In any case, the moral of the story is that the HXT outrunner will work, but it really really really needs a good ESC. And you should make sure your ESC settings are correct before taking it for a test drive. In the back of my mind, I'm wondering if the ESC was set to brake at throttle 0, which would have been disastrous.

p.s. A quick google reveals that a 78M05 is a voltage regulator chip. Makes sense that that would what blew. My guess is that when the ESC told the motor to brake, the motor said "sure, here's A GAZILLIO AMPS in back current to ya!" and that blew out a chip on the ESC.

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About this Entry

This page contains a single entry by Karen Nakamura published on July 24, 2008 8:26 PM.

Installed HXT motor (still waiting for ESC) was the previous entry in this blog.

Flea Market Find is the next entry in this blog.

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