First speed run with 100,000 rpm motor

[OptimaMan]

Hey guys, today I finally had a chance to use my 1515 5 turn motor (11,400 rpm/volt). I hooked it up in my TC4 with a ratio of 10.5:1 outside with a single 11.1 volt 2000 mah 15 C Kokam pack using a U Force.

I only got 50 mph - but it was because of the weak battery. My 15C pack actually gave out 100 amps!!!! But, the voltage dropped to FIVE volts!!! So, I was only able to hit about 60,000 rpm. I figure that this battery can only give out about 300 watts continuous and peak out at about twice that and it did. I didn't figure how much the voltage would drop though!

I will attach a graph of amp, voltage, wattage, and speed.

[OptimaMan]

Here is the voltage graph - in all fairness, this battery pack was cold. LiPos do not like to be cold. It was about 45 degrees F.

[OptimaMan]

Here is the speed chart - not too fast, but decently fast.

[OptimaMan]

Just so you know, it had a LOT of power. I had to slowly ease the throttle beacause it would spin out all four tires if I didn't. I believe a GP3300 6 cell pack would probably have gone faster than using a single 11.1 volt 2000 mah due to the voltage drop. A good 6 cell pack probably would not have dropped so much in voltage. Perhaps the motor needs an even smaller pinion so I could hit more revs? More tests to follow.

[OptimaMan]

BTW, that lipo pack swelled slightly... but unswelled after cooling down. Anybody else ever see this phenomenon? I charged it and used it tonight during my race and it was fine. Odd huh? I guess these cells are more robust than they look.

[OptimaMan]

I wasn't able to hold on the throttle for very long either. I don't believe I actually hit top speed - I ran out of street!

[Kmot]

How did you get those charts? :eek:

[OptimaMan]

Look at the "Extreme 1/10 sedan" thread. I have a picture of my TC4 with all sorts of electronic gadgetry to measure all those things. :) It's made by Eagle Tree and you just install it into your vehicle. They even have a wireless telemetry so you can see your speeds, temperatures, RPM, voltage, amperage, MAH used, etc. on a little LCD display that you stick onto your transmitter!!!

[TheSteve]

I hope you store your LiPo's outside, with the amount you stress them they could easily be ticking timebombs.
Aside from that I can't wait to hear a report when you have batteries that can handle the load. The motor absolutely sounds insane.

[DaFF]

Very interresting Opti !

We can see you far exceeded what this batt could take.

I wonder how a bigger lipo pack would do on the exact same setup...

BTW, what was the max G-Force you saw and what was the temp of batt / motor / esc ?

DFF

[TheMartian]

Does your system have much torque? With such a high Kv value, I don't believe that one can expect much torque... How much time does it take to reach the top speed ? Maybe it's obvious from the graph but my eyes are untrained :)
Another question is... do you think that GP3300s would be able to handle the current draw of your system?

[kufman]

Does the Eagle Tree software have the option to export to Excel?

[mac0326]

Perhaps if you ran two of these in parallel, you would also get better results. This is how I run my tc, and the batts are never even challenged (same batts).

[OptimaMan]

With a ratio of 10.6:1, there is PLENTY of torque. My acceleration graph shows 1 g of acceleration on a slick powdery street (just snowed, melted, and all that salt residue is really slick). I can't mash the throttle - too much power. I have to ease the throttle so I don't spin out. Without a doubt, having two in parallel should seriously reduce the voltage sag and let me really spin the motor - probably closer to 80,000-90,000 rpm. Voltage dropped from 12 to 5 which is a 7 volt drop!! If I got it to only sag to like 8-9 volts, I'd get a good 30,000 more RPM.

Yes, you can export to excel.

BTW, I have a spare backup eagle tree. If anybody is interested, give me a PM. It's brand new - I bought two (on accident - long story) and it was too late to return them so I have one brand new one just sitting in its box.

[OptimaMan]

GP3300's should easily handle the current draw of this motor. Actually, I believe that this motor would be excellent for 4 or 6 cell 1/12 racing or lightweight TC with LiPos. Once again, a nice 6cell gp3300 probably will stay around 5-6 volts under that currrent draw and so you should be getting about 50-60 mph with that same ratio using only 6 cells.

[glassdoctor]

Like TheSteve said, be careful with that lipo pack. It's normal for a puffed cell to "unpuff" itself, but that doesn't mean it's ok. It likely is still damaged, and will lose performance or even flame out...

So keep it outside...

Guys at rcgroups.com have reported puffed packs that seemed to work fine after that, but others have had them crap out. I think most guys say to just dunk it in salt water and toss it.

[glassdoctor]

As for the speed run... you definitley need more battery. 2000mah 15C is ok for "normal" TC use, but not your speed run.

You pulled 100 amps, which is 50C for your pack. If you parallel two of these packs I bet there would be a dramatic difference in voltage drop, like maybe a drop of 2 volts or less instead of 7 volts...

I would love to see the results if you keep testing...

[studysession]

Dunk it in salt water?

[glassdoctor]

That's to "kill" the pack so it's safe to dispose of it... no fires or explosions...

[studysession]

You mean dump it on the ocean or just like a water jug of salt water? Never heard of this.

[glassdoctor]

A container of water with a lot of salt, like add a half cup of salt.... I've never done it myself. The info comes from www.rcgroups.com

Actually my vote would be to use a bad cell as an experiment. Overcharge it or abuse it in some way until it explodes, for educational purposes only of course. ;)

And get it on video tape..

[glassdoctor]

Here is one thread I found real quick about the salt water....

http://www.rcgroups.com/forums/showthread.php?t=277738&highlight=lipo+salt

[studysession]

I find that interesting - thanks.

[Rotary Rocket]

...BTW, I have a spare backup eagle tree. If anybody is interested, give me a PM. It's brand new - I bought two (on accident - long story) and it was too late to return them so I have one brand new one just sitting in its box.
OptimaMan, I am interested in you "spare" eagle tree.

Please email me at LB9731@sbc.com.

Thanks.

[starluckrc]

I've soaked a pack and flamed a pack for fun. I'll have to get the next flamer on video. If the pack swelled, then it probably has microscopics shorts inside and is dangerous. They can go up quite violently.....speaking from experience.

[OptimaMan]

Yeah, I've punctured one for fun. Then I smashed another with a hammer to see what would happen. Then I direct short circuited one. They all end up with bad results. :) The one time I mischarged one at high amperages, my whole house burned up!

They should make a "vent' on these things. So, instead of the wrapping bursting and igniting, they should allow it to vent through a small opening and it should have an indicator showing that the cell is vented an no longer good to use. Or better yet, Lipos should be made and then wrapped with woven fiberglass fabric. It'll add just a couple of ounces at most, but even if they blow, they won't "blow". It'll burn inside the wrapping or gases might just leak through the fiberglass fabric. Hey, maybe somebody will make this and test it out! Oh, how about a circuit - once temperatures or pressures exceed a certain level, it should open the circuit to prevent charge/discharge until the safe level is reached again.

[D.J.]

These batterys sound like fun. Are they spendy?

[glassdoctor]

Optima, are you using any charge safety devices? I figured you would be, after your experience. There are circuits like you mention... and I know of a couple new ones that should be out soon, like Thunder Power's new one.

I'm going to use the Polyquest packs and their PCM guard. It's an automatic cutoff circuit that plugs between the charger and battery. This little thing may have actually saved your house, IF it was overcharged lipos that did it.

At the very least it can't hurt to have a "safety valve" even if it's not perfect.

[ronin8451]

I run these exact same batteries in a very large brushless powered airplane and you must not go over 30 amps per paralleled cell ! I pull 52 amps on a 6S2P pack and the voltage drop is only 3 or 4 volts max. at full throttle. I plan to use these in a 1/8 scale buggy conversion with a Lehner Basic 4200 XL and will add another set of packs in parallel for a total amp draw capability of 90 amps.
The big factor in these packs venting is that the Lithium inside reacts with oxygen, that's what ignites when they are burst open. NEVER smash one with a hammer !!! I have had one burst on me in a crash of a plane and the flames were huge , with a smoke cloud 15 feet in diameter ! :eek:

Rick

[glassdoctor]

A real Hollywood airplane crash, cool!

ronin, are you going to use a gear reduction on that 4200XL? That's really high rpm for a 1/8 with the stock drivetrain ratios. A 2:1 unit would be good...

That voltage drop sounds much better... 3-4 volts on a @24 volt pack..

[ronin8451]

I am not going to run those exact packs, just the same 2000 HD Kokam cells, but in a 3s3p pack configuration . In a 6 S configuration I would probably go too many RPM's for this motor ! LOL !

Rick

[uncle_jo3]

were could i get one of those motors? i really want to put one on my car if you dont want to post if email me at uncle_jo3@yahoo.com thanks

[glassdoctor]

The Lehner? A couple places...
www.rc-monster.com
www.finedesignrc.com

[OptimaMan]

I just charge them in a steel toolbox with the lid locked! (Now, I have an explosive grenade!!!)

I'm beating up on my lipos on purpose actually. I want to push the envelope of what's possible and allowed for these lipos and I'm trying to do it in a controlled environment. I always keep them in a steel toolbox now. My wife wants me to get a safe and leave them in a fireproof safe instead.