long lost newbie lipo questions

[JohnRobHolmes]

Take it easy there sport. You described a bad startup (cogging) and the voltage was shown to be low. Batteries provide the power for startup, the motor only does what it is told. If the voltage falls too low, startup will not occur properly. 130f is not hot, but the increased temp would be caused from bad startups.



I have a few years of lipo and brushless under my belt too, but "god forbid" anybody listen to suggestions from me. Drop your voltage cutoff down to 9v and see what the battery does on the 55t.

[JAM MaxAmps.com]

John look at the graph for the 55T you'll see that I made it go below 9.6 volts and right down to 9.2 volts by holding the AX-10 on the carpet and making it dig. It didn't skip a beat. Ans seeing as that you have been at this for a while I take it you have had a bearing go bad on you before in an outrunner. And everyone knows that the amount of drag created by a bearing will increas the amp draw and use more voltage. Well That is what the motor acted like. Now if it was a pack that couldn't handle the motor we all know that it would have cogged everytime I dumped the throttle and as you can see in all the spikes in the graphs that exactly what I was doing. Both on the carpet, hard wood floors, Pillows plied up and the plywood ramp with the 2X4's. It only stalled, froze, hung up or whatever you want to call it towards the end of the 20 minute run when it was hot and when I was on the hard wood floor. Everyone one knows that isn't going to crate a high load on the vehicle. If the pack wasn't up to the task it would have cogged on every start up and sure as hell wouldn't have made it 20 minutes, hell it would have puffed or come of the rig at 130 degrees instead it came of at 74 degrees and in great shape.

More test results are coming.

jason

[JohnRobHolmes]

A lipo doesn't have to be hot to be overdrawn. I am not putting down your brand, I am stating that the voltage depression indicates that you need more battery (mah). If you reduce the voltage cutoff and the pack dips lower, you have the first indication that more amperage overhead is needed. With no lvc the battery should not fall below 3v/cell minimum. I would give you some battery suggestions based on the last year of data logging I have, but you need to do testing yourself.

If you indeed have a bad bearing, the Crawlmaster has a two year warranty.

[Reflection]

Originally Posted by JAM MaxAmps.com

I'm not trying to bash on John's Motors at all so please don't make it sound like that.

Jason

I'm not. The reason I said that was merely the fact that a 55t draws less amperage than a Crawlmaster and puts out considerably less power,so,you'll see a difference in the results.

Just like my 3025-8. You can't compare amp draw or anything between this motor and a 55t. You can get AA cells to start a 55t spinning and get marginally decent performance. AA cells would do good just to get my big out runner spinning,in my 12 pound pig on flat ground On sub C's or a big 3 cell,it'll light'em up.

I see where your going with this. Happy testing

[andrewhendler]

not that this has alot to do with this but for crawler motors it would be better if we could get kt ratings instead of kv ratings

[JohnRobHolmes]

kt can be derived from kv, as they are inversely and directly correlated.

[JAM MaxAmps.com]

Andrewhendler here's a 15 minute run on a MaxAmps 3S 1550 with the 55T lathe motor. Test was cut short because I hit the ramp to hard and fast causing the Front Stock Servo horn to strip out. Putting on another an the testing will go on.


Low Volts: 9.73

High Watts: 221

High Amps: 21.53

mAH used in 15.07 minutes was 535 of 1550

Motor temp was 106 degrees with esc and battery cool to the touch.
Attached Thumbnails

[andrewhendler]

Found it.
Kt = 1352.4 / Kv

Kt in oz's

Thanks Jason

[JAM MaxAmps.com]

Motor has been swaped out to the CMS and the same pack is charging up. Servo horn has been replaced also.

Jason

[JAM MaxAmps.com]

Adrewhendly here ya' go.
The test run on the CMS with a 3S 1550. It didn't go so well the motor gave up a bit of the ghost. only a couple of minutes into the run and the motor did the same thing as the 860 3S saddle pack not only that but the temp of the motor went up to 222 degrees and let out some light smokeat the end of the run.I stopped the test when I started to smell the motor. The run only lasted 10 minutes 25 seconds. This test was run on the smooth cement floor in my basement. First two spikes in the graph are me holding it back while full throttle was applied on the carpet in the other room once the motor got hot the stalling or freezing started again and as I stated it let smoke out at the end when I took the temp at 222 degrees notice the esc is only 111.9 degrees. The battery was warm but not bad at all.

Low Volts: 6.33

High watts: 696

High Amps: 101.62

Total mAH used in the 10 minute run was 1007
Attached Thumbnails

[andrewhendler]

you were almost pulling 1 hp at peak, I dont know enough of the specs on the motor to make any assumptions, where or what side of the motor did the smoke come from?

[JAM MaxAmps.com]

The smoke came from the windings. These motors have no cooling holes in the end of the bell like most outrunners. Under normal crawling it is a good motor. And this is a sport class not the competition grade one.

Jason

[JohnRobHolmes]

With a low voltage of 6.33 you probably ruined the battery at the same time as the motor, not as an immediate poof but as reduced capacity over time from internal shorting. I am guessing the LVC was turned off. I would like to inspect the motor to see if there is a bad bearing, or if you just overloaded it and caused a dead short. It would be good for learning.

[JAM MaxAmps.com]

The Battery came off warm but no warmer than some of the planes I use it in. So I'm not worried about that. And unless the new update from Castle has some how disabled the LVC point it is on and set at 9.6 volts. And I double checked it. No dead short either I ran a continuity test on the leads and nothing there. I also checked the resistance of the windings with my multimeter but more of then enough the multimeter leads create more resistance than the motor windings. Although the readings were the same for all. And as for the bearings no discoloration and they spin freely. I'm gonna take a guess and say the magnets are not liking the heat when the motor gets loaded and hot. Once the motor cooled back down it did run fine and still has lots of power. I think the smoke was from the windings and if I would have pushed it any farther it would have melted of the coating which then would have caused a dead short. John I'll be at the Indoor comp on March 1st I'll bring it with me and you take it back to have a look to see what the cause is. I'm gonna do some normal running with it and see if it acts normal in the mean time.

Jason

[JohnRobHolmes]

I will be interested to see how the motor looks. The sport version isn't rated as high temp as the normal version of the CM. Take the endbell off and check for continuity between the stator plates and winds. I still stand by my notion that the horrible sounding startups were caused from depressed battery voltage. I have seen it, logged it, experienced it thousands of times. If there is no source for stalling resistance, the battery is the first culprit for any bad startups whether it happens every time or just once in a run. Jamming the throttle on an outrunner demands huge amp bursts, as you have seen. Each phase wind is shorter than a similar speed 3 slot brushed motor, so the phase resistance is much lower. If the battery doesn't supply, the ESC can't keep the motor in phase and the situation gets noisy and hot.


So are you saying that running your 3 cell lipo down to near 6 volts isn't bad for it?

[Mortimer Snerd]

I'm having the same problem you're describing on my 55t with a Sidewinder, mostly when the servo is turned. I'm really curious about what conclusions you come to, as it may give me a solution.

[JohnRobHolmes]

If a turned servo is causing shutdown, the BEC is most likely the culprit. Do you have an RX pack or external BEC to try?

[Cloak]

Jam: Would you mind running 2 sets of those packs in parallel to see if that helps the Sport motor and pasting the charts and your impressions.

Edit: Ahh, it was the sport that was smoked. Well heck, there goes that idea.

[JAM MaxAmps.com]

Originally Posted by Mortimer Snerd

I'm having the same problem you're describing on my 55t with a Sidewinder, mostly when the servo is turned. I'm really curious about what conclusions you come to, as it may give me a solution.

I'm running with 2 servo's and a Castle BEC set at 6 volts but the seezing was only happening when I was trying to take off at full throttle when the motor got warm. I never had issues when turning.

Jason

[Cloak]

Originally Posted by Mortimer Snerd

I'm having the same problem you're describing on my 55t with a Sidewinder, mostly when the servo is turned. I'm really curious about what conclusions you come to, as it may give me a solution.

I had the same problem with both a 55t and an outrunner, I put my cc bec in and it went away. I haven't taken readings yet, but I'm guessing the bec on that sidewinder is a bit odd. It did it on those new towerpro servos run2jeepn sells and a hitec 645.