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ESC problem?...need ideas

ESC problem?...need ideas

Old 04-10-2010, 12:57 PM
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JSR
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Default ESC problem?...need ideas

I picked up a set of new batteries for my buggy and just tested it out today on my street. When I accelerate, it accelerates hard and hits a certain speed just before I'm at full throttle, then it seems to slow down a bit and holds a slower top speed when I keep the throttle at max.

So, using dummy numbers, when I accelerate, at about 3/4 throttle, it's accelerating hard and is at about 35mph and seems to want to hit a top speed of 40mph (just an example speed), but as I continue past 3/4 throttle, it seems to slow down a bit and tops out at about 30mph. The new batteries are 5800mAh 25C whereas the old packs were 3000mAh 30C, so the new packs should be able to support the speed. It's actually faster with the old packs which are getting quite old. Any ideas on what might be going on? The new packs are much punchier, as expected, but the top speed seems to be a problem. I can even hear the pitch of the buggy (the sound from the gears) drop as I go past 3/4 throttle, so something is slowing down.

The ESC is hotter than it was with the old batteries, but still not here thermal temp (hitting 130-140F now, was around 120F).
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Old 04-10-2010, 02:25 PM
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not sure what you are running. Sounds like motor is wanting more power. Are the batteries warm after running?
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Old 04-10-2010, 02:46 PM
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The c rate must be false. Also the 5800 packs probebly weigh a couple hundred grahms more. What type of batteries are these? Sounds like the batteries don't have the c rate to keep pulling the rpms, like they are 25c burst instead of 30c constant! You would think they would out perform the smaller batteries. Weird.
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Old 04-10-2010, 02:57 PM
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When you go back to the original batteries, is the performanc eback to normal, or is it now messed up and slows at high throttle with those too?
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Old 04-10-2010, 07:51 PM
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I just tested it with one of he old packs and it still does it but occasionally will go to full speed at full throttle. Sometimes it cuts back and forth between the lower speed and true top speed. So it seems its not isolated to the new packs but it consistently does it with the new packs. It did seem to get to full speed more often as the old pack drained more so maybe its worse with the new pack because it holds voltage better.
The new packs are Turnigy packs so they should be correctly rated. Others have the same packs and they perform fine. Looks like its an ESC problem but what? Nothings been changes since it worked fine. Unless the huge jumps at the track finally took its toll.
Any ideas? Thanks for any help.
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Old 04-10-2010, 09:55 PM
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maybe something in the drive train wore out and binding.
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Old 04-10-2010, 11:01 PM
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Originally Posted by JSR View Post
I just tested it with one of he old packs and it still does it but occasionally will go to full speed at full throttle. Sometimes it cuts back and forth between the lower speed and true top speed. So it seems its not isolated to the new packs but it consistently does it with the new packs. It did seem to get to full speed more often as the old pack drained more so maybe its worse with the new pack because it holds voltage better.
The new packs are Turnigy packs so they should be correctly rated. Others have the same packs and they perform fine. Looks like its an ESC problem but what? Nothings been changes since it worked fine. Unless the huge jumps at the track finally took its toll.
Any ideas? Thanks for any help.
What ESC is this?

Try re-calibrating to your transmitter as well. With my Castle ESC's. I like to set my end points to 98%, calibrate, and then set the end point back to 100%. his ensures I get full throttle and brake, but not by too much. The Castle ESC's also have the 3 leds, and it gives a solid green for full throttle and a solid red for full brake. If I see the LED flashing, I know I am not hitting true full throttle.

With the motor running, try shaking the ESC hard, see if it hickups. If it does, you mave have broken a trace or a solder joint in th ESC. Hard jumps can certainly take their toll.

I also have to sgree, check all your bearings, you may very well have a bearing locking up dragging things down. If you have a good amp meter, you can check this. Rev it up and watch the current, and when you hear it slow, is it pulling more current or less? If the current goes up, something is binding.
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Old 04-11-2010, 09:24 PM
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Its an EZrun ESC. I did recalibrate it the same way I've always done but no change.

Here's some more data:

I ran the old pack more. As I ran it more it would hit full speed more often. Seems like it is related to voltage. The lower the voltage got the more often it hit full speed.
Ran the new pack and found out that if I roll into the throttle very slowly it would hit top speed (which is faster than with the old packs) but if I get to full throttle too fast it wouldn't reach full speed.

I checked the drivetrain and all is smooth.

Any ideas why higher voltage or faster to get to full voltage would make it not hit full speed? It doesn't look like a drivetrain problem to me.
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Old 04-11-2010, 10:11 PM
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kinda related but unrelated, I have a 1/16 revo that does the same thing on 4s. If you ease off the throttle a little bit it will pick up speed, at wot it slows down. Recalibrated, different radios, all the same. Only does it on 4s, works as usual on 2s, and 3s. I had another hw esc that if you slam wot from a dead stop, it would just sit there, like it didn't recognize or recieve the signal. If you went wot at all but a slam it worked perfect. It has to be something voltage related with your problem. Seems like it has been brought up on the rcm board with mmm esc's in the past as well, might do some searching there.
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Old 04-12-2010, 07:46 PM
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Have you carefully checked the connections on the esc? Are any of them getting warm? May have one going bad and its intermittent.
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Old 04-13-2010, 02:45 PM
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I checked the wiring and couldn't see any physical issues. I don't know if there's a specific wire or joint that's getting hotter than others though. It's a pretty small ESC and feeling around with my finger is tough. And my IR temp meter isn't small enough to target a tiny area like a solder joint.
The issue isn't intermittent...it's repeatable. I just can't figure out what would cause such a thing. The only thing I can think of is component breaking down at the higher voltage and creating a short. Possible cap or maybe an internal diode. No clue.
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Old 04-14-2010, 02:31 PM
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This can be caused by the rev limiter that is built into some esc's. This usually isn't a big problem these days but it used to happen all the time with 6-pole motors and older esc's. I know Castle's controllers can spin a 2-pole motor over 100,000 rpm. I don't know about other controller builders.
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Old 04-14-2010, 04:35 PM
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That might explain it if this were my first time running it, but I've run this setup for quite some time now and haven't had problems with it till just recently. Unless that internal limit got changed because of damage to an internal component due to impacts from the big jumps.
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Old 04-20-2010, 10:38 PM
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Well I reprogrammed all the settings and changes the caps and it still does it. I can't think of anything else except that the ESC itself hs a problem. While programming it I noticed that it wouldn't let me set punch to higher than 4 when there should be 9 levels. It still runs if I set the EPA on my radio to no more than 85%. Otherwise it has that cutting back problem that starts to heat the ESC. Probbly an internal component that's breakdown voltage reduced so now its shorting a bit at higher voltage. Unless someone can offer more ideas.
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