Oh #%@!! What did I do to my SMC Lipos? - RC-Monster Forums

07:43 PM

Ok, I think I just seriously bit the weenie on this one. I just finally got done upgrade my Savage Flux with a new Spektrum DX 2.0 with some Proline Badlands and Velocity dish wheels. I programmed the DX 2.0 as per the usually HPI way and made sure the EPA's were at 125% for throttle and brake, as I was told this would not hurt the motor or the ESC. The throttle only had 10 clicks for trim. I kept the gearing stock at 20/44.

I"m using SMC Sport Max 6000mAh 28C hardcased batteries which have been awesome batteries up until this point. I've been using a Triton 2EQ with balancer at each and every charge and iv'e had the LVC set from 3.0v to 3.2v using the Castle link.

Today was my first day running the new truck and I kept it simple and was just running it in average grass height at a variety of speeds testing out the new tires and rebuilt shocks. I kept checking the temps and I didn't feel the motor, ESC or batteries were getting dangerously hot.
It was working good for around 15 or so minutes when I noticed it started to loose power pretty quickly, more then it used to.

So I shut it down and brought it inside and I about had a cardiac arrest when I took out the batteries that were very warm to the touch and had damn nearly puffed out of the hard pack casings!!

I immediatly put them outside to cool off and hopefully not explode, so I haven't taken a voltage reading on the charger but the LVC was set at 3.1v and it didn't kick in at any point, I just noticed a loss in power sooner then I expected.

Anyone please give me incite or suggestions on what the hell went wrong here? I'm pissed that just ruined $190 worth of batteries and I don't know how or why!

EDIT: Added photo of voltage test results for both Lipos

lincpimp · 07.19.2009, 02:39 PM

Well, looks like one or more cells in that pack puffed. Most likely due to the the grass putting addl load on them and they could not keep up. Given their specs they should be able to handle a 168 amps cont, but we all know that the specs are sometimes a bit exaggerated. Plus I have no idea what cells are in there, so you may have just got a defective cell, it happens.

4s setups in heavy monster trucks are just not a good idea. I have stressed higher rated packs that those smcs in a revo on 4s, so I can imagine the savage was pushing them pretty hard. The grass was probably just enough to send them over the edge.

Time for some hyperion g3 packs! Go up to 5s, and gear down to a 17t pinion for the same overall speed. 5s seems to be the sweet spot for the MMM/2200 setup anyway. I ran my lst with the mmm/2200 on 4900 5s rhino lipos (70 dollar pack, 20c rated) and it did fine with badlands, geared for 40mph. Not a light truck by any means, and those batteries had no issues keeping up.

Going up in voltage will reduce the amp draw, provided you lower gearing for the same overall top speed.

Metallover · 07.19.2009, 04:53 PM

Might have been the new wheels, in addition to the grass. Are the new wheels bigger/heavier then the old ones?

_paralyzed_ · 07.19.2009, 05:03 PM

did it roll freely after the new wheels were on? I always "kick" my r/c's before I run to make sure they roll nice. Any drivetrain binding puts serious load on the equipment.

07.19.2009, 05:32 PM

Quote:

Originally Posted by Metallover

Might have been the new wheels, in addition to the grass. Are the new wheels bigger/heavier then the old ones?

About same size, but weight less then the other ones.

Quote:

Originally Posted by _paralyzed_

did it roll freely after the new wheels were on? I always "kick" my r/c's before I run to make sure they roll nice. Any drivetrain binding puts serious load on the equipment.

Yeah, it rolls fine

Quote:

Originally Posted by lincpimp

Well, looks like one or more cells in that pack puffed. Most likely due to the the grass putting addl load on them and they could not keep up. Given their specs they should be able to handle a 168 amps cont, but we all know that the specs are sometimes a bit exaggerated. Plus I have no idea what cells are in there, so you may have just got a defective cell, it happens.

4s setups in heavy monster trucks are just not a good idea. I have stressed higher rated packs that those smcs in a revo on 4s, so I can imagine the savage was pushing them pretty hard. The grass was probably just enough to send them over the edge.

Time for some hyperion g3 packs! Go up to 5s, and gear down to a 17t pinion for the same overall speed. 5s seems to be the sweet spot for the MMM/2200 setup anyway. I ran my lst with the mmm/2200 on 4900 5s rhino lipos (70 dollar pack, 20c rated) and it did fine with badlands, geared for 40mph. Not a light truck by any means, and those batteries had no issues keeping up.

Going up in voltage will reduce the amp draw, provided you lower gearing for the same overall top speed.

Theres no way the grass would have put that much strain, considering that i've run the truck with the same batteries on the stock tires with no such issues.

I'd rather not deal with trying to modify/run a 5S pack on a Flux, its not specced for that type of wiring/Lipo.

Metallover · 07.19.2009, 05:37 PM

Just use a 2s and 3s pack in a series to make 5s. A hyperion 5000mah G3 vx 2s and 3s lipo.

lincpimp · 07.19.2009, 05:48 PM

Quote:

Originally Posted by Freezebyte

Theres no way the grass would have put that much strain, considering that i've run the truck with the same batteries on the stock tires with no such issues.

I'd rather not deal with trying to modify/run a 5S pack on a Flux, its not specced for that type of wiring/Lipo.

Not to point out the obvious, but the lipo did puff. They only puff if they go way under voltage and have a large load placed on them, or they are over stressed past their capabilities.

And running in grass places more load than almost anything else (save maybe deep wet sand or mud).

As ML said, use a 3s and a 2s. Heavy trucks need more voltage dude, not talking out of my ass here (even though it would be cool if I could do that).

sikeston34m · 07.19.2009, 06:17 PM

Quote:

Originally Posted by lincpimp

Heavy trucks need more voltage dude, not talking out of my ass here (even though it would be cool if I could do that).

Jim Carey did that on that one movie.

Finnster · 07.19.2009, 06:17 PM

Quote:

Originally Posted by lincpimp

Not to point out the obvious, but the lipo did puff. They only puff if they go way under voltage and have a large load placed on them, or they are over stressed past their capabilities.

And running in grass places more load than almost anything else (save maybe deep wet sand or mud).

As ML said, use a 3s and a 2s. Heavy trucks need more voltage dude, not talking out of my ass here (even though it would be cool if I could do that).

I did that once on a dare.. was funny for a bit, then just made my tongue taste funny.

Grass is the worst you can put a pack thru. Lots of people think speed runs are really hard on batts, but they are relatively light duty unless the gearing is v. v. tall.
Hard to imagine it got fragged that easy, then again could be the way you drive it or a bad pack. Eagletrees are invaluable things, as are temp guns. Hot lipos are over worked lipos and soon to be dead lipos. Sry.