6s drop off

[spcpicard]

Ran my 8ight T first time Thursday, than raced it Sat in the Louisiana point series. I am running a MMonster esc with a Xcelorin 1300kv motor with a Hyperion 30c 3200mah 6cell. The qualifiers went fine, but during the main I noticed a considerable drop in performance after the 5min mark of the 10 min main, I burned 1801 mah in about 10mins and 20 sec. I am geared 43/15 which is calc for about 39mph. I noticed the same thing from practicing with it on Thursday so I increased the timing to 10 and I thought I would be good, but during the main on Sat, the extremely noticable performance drop casued me to drop from 3rd to 4th. My question is, is this normal when running 6s packs? I've run 4s and 5s pack and all of them have a slight drop off but none were nearly as noticeable. I am guessing that maybe it's just that the xcelorin motor just isn't providing enough torque? Any how I just bought a tekin 1350, but now I am going to be worried about the rotor sep issues. Any ideas would be appreciated since I am new to the whole 6s and truggy deal. Here's some pics of my new ride.





BTW if anyone is in the area, the LA point series had 16 in the 1/8 ele buggy class and 8 in the e truggy class....it's really taking off!

[BrianG]

A truggy on 3200 cells might be pushing the 30C rating depending on weight. And 3200mAh is not much runtime, but should be good for 10-12 minutes based on a 300w average power draw.

What LVC point are you using?

And as far as the rotor seperation of the Tekin motors, just think of it as having a slipper inside the motor.

[lutach]

That motor would be great for 8S 3200mAh geared for the same speed. I'm using a Neu 1515/2Y with 8S lipos and I can easily get over 20 minutes of run time on my old packs. I noticed you have a couple of 6S 4100mAh, did you sell those?

[spcpicard]

Originally Posted by lutach

That motor would be great for 8S 3200mAh geared for the same speed. I'm using a Neu 1515/2Y with 8S lipos and I can easily get over 20 minutes of run time on my old packs. I noticed you have a couple of 6S 4100mAh, did you sell those?

sold one of the 6s and rebuilt the other into a 4s for my buggy. 8s would be way to heavy for my liking, I'm all about running as lite as I can thats one of the reasons I was selling the brand new 6s 4100s....I loss close to 4oz going with these.

[spcpicard]

Originally Posted by BrianG

A truggy on 3200 cells might be pushing the 30C rating depending on weight. And 3200mAh is not much runtime, but should be good for 10-12 minutes based on a 300w average power draw.

What LVC point are you using?

And as far as the rotor seperation of the Tekin motors, just think of it as having a slipper inside the motor.

3.5 volts/cell, the same I've always used, I was thinking it may be the lvc but seemed to be a little fast for 50%, now that I think about it though it does seem to change all of a sudden, would suck if I just bought the tekin when all I had to do was lower the LVC.

All the races I'll be in will be 10 min mains.

As far as weight I am thinking I am on the lighter side according to some nitro burners. Ready to hit the track weight is 9lbs 8oz with the heavier set of tires.

[spcpicard]

Originally Posted by BrianG

And as far as the rotor seperation of the Tekin motors, just think of it as having a slipper inside the motor.

The funny part is my xcelorins did the same thing when I first ran one back in Sept, but Losi was quick to figure out the problem, maybe tekin should learn from them and go to the CF wrap and keyed ends on the rotor.

[BrianG]

3.5v/cell is kinda high for an LVC value IMO. The voltage does dip on hard acceleration, and the closer you run to it's max discharge value, the more it will dip. So, when the pack is sitting at it's 3.7v nominal value, 0.2v isn't giving much leeway for voltage drop. I would go to 3.2v, or 3.3v/cell. Still allows plenty of safety zone, yet provides ample compensation for v-drop and more runtime.

[spcpicard]

Originally Posted by BrianG

3.5v/cell is kinda high for an LVC value IMO. The voltage does dip on hard acceleration, and the closer you run to it's max discharge value, the more it will dip. So, when the pack is sitting at it's 3.7v nominal value, 0.2v isn't giving much leeway for voltage drop. I would go to 3.2v, or 3.3v/cell. Still allows plenty of safety zone, yet provides ample compensation for v-drop and more runtime.

I'm headed back to the track on Weds, when the power drops down I will try switching the power off and then back on, this should tell me if it's the 50% lvc kicking in.

[lincpimp]

Go with 3.1v per cell. You must be hitting the lvc. I have run those cells with good success myself. I have a feeling that you are pushing them pretty hard in a truggy. I run 5s packs of them in my hyper buggy. Go with a 5s pack of larger mah cells and a 2000kv motor, or the cc 2200 motor, great 5s motor, especially geared for 40.

You are geared pretty high, and have lower motor rpms.

[Patrick]

I wouldn't give up on the setup yet. Just change your LVC to about 3.2v per cell +or- .1v. Maybe go down to a 14t pinion or change to the losi 47 or 48t spur, and probably put the the tekin motor in. Your motor rpm is a little low, but it's still high enough to work well. Your packs have the same watt hours and watt output as a 4s 4800mah pack, so there's no reason they shouldn't work when geared for the same speed as the 4s setup. About 12 mins race runtime is about the most I would expect from them though. Once you've tried that stuff (especially the LVC) then decide about the setup.

[spcpicard]

Yeah I am really starting to think that that it was the LVC kicking in, I will go to the track tomorrow am, as far as run time 12mins is plenty since we are doing 10 min mains and 5 min quals. I may have a new tekin motor for sale if the xcelorin works out.

[spcpicard]

Originally Posted by Patrick

I wouldn't give up on the setup yet. Just change your LVC to about 3.2v per cell +or- .1v. Maybe go down to a 14t pinion or change to the losi 47 or 48t spur, and probably put the the tekin motor in. Your motor rpm is a little low, but it's still high enough to work well. Your packs have the same watt hours and watt output as a 4s 4800mah pack, so there's no reason they shouldn't work when geared for the same speed as the 4s setup. About 12 mins race runtime is about the most I would expect from them though. Once you've tried that stuff (especially the LVC) then decide about the setup.

Yeah I race with a 4s 4100 neu energy on a 1512 3d in my buggy (also on 3.5v/cell cutoff) and it has plenty of power the whole 10 min main, that's why I figured the 3200 6s would have just as much or more, of course the china cells in the neu batteries may have a one up on the enerland cells in the hyperions

[BrianG]

If you get ~12 minutes of runtime with 3200mAh cells at 6s, that's an average current of 16A, and an average power of 355w. A bit higher power needed than I would expect, but whatever. Anyway, the burst amperage is probably around 100. That would equate to over a 30C rate burst. At those levels, voltage WILL dip and trip your LVC. The funny thing about the C rating is that they never state at what voltage it will maintain. So, if they rate the cells at 30C, but at a voltage of 3.0v, this would make sense.

Your buggy probably requires around 225w average power. That would mean that 4s 4100Ah pack is running at 15.2A average current, which nets you around 16 minutes of runtime. Bursts are probably a little lower percentage-wise than the truggy due to the smaller/lighter vehicle, more ideal gearing, etc, so figure ~90A. That's 22C. Makes sense to me that it could handle a higher LVC point without early cutoff.

[spcpicard]

Originally Posted by BrianG

If you get ~12 minutes of runtime with 3200mAh cells at 6s, that's an average current of 16A, and an average power of 355w. A bit higher power needed than I would expect, but whatever. Anyway, the burst amperage is probably around 100. That would equate to over a 30C rate burst. At those levels, voltage WILL dip and trip your LVC. The funny thing about the C rating is that they never state at what voltage it will maintain. So, if they rate the cells at 30C, but at a voltage of 3.0v, this would make sense.

Your buggy probably requires around 225w average power. That would mean that 4s 4100Ah pack is running at 15.2A average current, which nets you around 16 minutes of runtime. Bursts are probably a little lower percentage-wise than the truggy due to the smaller/lighter vehicle, more ideal gearing, etc, so figure ~90A. That's 22C. Makes sense to me that it could handle a higher LVC point without early cutoff.

Not sure how much runtime since I've never drove it longer than the 10min main, I didn't even do a practice lap since I just pretty much got it. I'm sure you're right about the cutoff tripping, but the reason I went with 6s on the truggy is because I figured it would pull less amp from what the motor specs were, but any how I will let you know how it goes tomorrow, now I'm off to soldier a deans on the 1/16 mini revo some one just dropped off to me

[spcpicard]

Just an update, I did drop the cut off to 3.1/cell, and it did seem to help, but the motor still didn't have enough pop after about 5 or 6 mins. I went ahead and swapped in the tekin 1350 and it definitely cured my problems, I ran past 12 mins and it still had plenty of torque, less than at the 5 min mark, but definitely raceable unlike the xcelorin. I am guessing that the extra rotor length with the tekin is helping. I stopped shortly after 12mins but my pack still didn't dump so I am all good for racing 10min mains. The pack did however come off alot warmer than I am use to with my neu and zippy packs. So as long as my slipper clutch on my tekin rotor doesn't kick in, I should be all good. Thanks for the help to all the guys how made suggestions.