Lipo getting untouchable hot

[soheilmd]

Today i was playing my kraton 8s and noticed that it sometimes stop working like out of range while car wasnt even that far. I opened the body and noticed the lipo is untouchable hot. What causes the lipo to get this hot?

some facts:
kraton 8s
max5 5613 combo
gens-ace-r-spam 5000 50c
outside temperature 23 celsuis / 73 fahrenheit
playing on a leveled verry short dried grasfield without doing any jumps

 

[Snowmandk]

You are pulling too many amps from the batteries.
Gear down to reduce load on the batteries or get better, higher mAH lipos.

Do your connectors get hot too? Maybe a bad solder joint is causing high resistance somewhere in the wiring.

Also, check the internal resistance of your lipos, they might be going bad.

 

[soheilmd]

No connectors not getting hot. I think gearing down would help. Motor is getting hot too. But i didnt know that would heat up the batteries too.

Thank you

 

[SrC]

Absoutely gearing down, if you haven't already ruined a fews Lipo cells already. Check the IR's well. I find if a Lipo pack reaches 120F+ degrees, consistently, permanent damage might result. Not to mention a potential Fire.
If you don't have a temp gun, that is your first mistake there. I would first buy one. The only way to make sure your motor stays below 150-160F and lipos below 120F, watching the ESC and connectors as well.
Merely "touching" cant say what Hot truly is.
The fact that you say from touch, the motor and Lipo is hot means you are "likely" overgeared. Just not a definitive diagnosis at all....
8s rigs weigh a heavy 30+ pounds. Gearing matters.

 

[jkflow]

Grass is the worst for bashing with respect to heat issues, gear down is the only thing that helps.
Temperature increase is exponential if you drain below 3.7'ish.
The worst I had on a lipo was 175F, and I was pleasantly surprised it didn't go up in flames, anything above 140'ish will greatly diminish capacity going forward. FYI, Lipos can catch on fire when above 160'ish, called thermal runaway, don't try to beat my record.

 

[SrC]

+1.
I find that 120F is as high as you want to get with lipos.
My personal rule. Hot weather running is also part of this.
Sometimes just needing to gear down for the summer months.

 

[jkflow]

My 'normal' is ~140F in boats, cars I'd like to stay in the 120F range as well.
Life expectancy does go down, trust me on that.

 

[soheilmd]

Is there a way to gear down without losing much speed?
That thing is a beast would hate to lose speed

 

[jkflow]

No such thing other than getting a better motor, lower kV and larger pinion to maintain speed at lower temps.

 

[john 8s]

Gear down a few teeth and check temps often then gear up or down keeping an eye on temps. A little less speed is better than watching your car go up in smoke

 

[RC-Dude]

MC Hammer: "Don't touch this". Dang da-di dang. "Don't touch this".

I bet his RC car lipos got too hot. And he was just emotionally processing it.

 

[jkflow]

By all means, get a thermometer/thermal gun and give actual values next time. Untouchable is 1000F i.e. no gauge as to what you consider 'hot'.

 

[soheilmd]

By all means, get a thermometer/thermal gun and give actual values next time. Untouchable is 1000F i.e. no gauge as to what you consider 'hot'.

Just bought one five minutes ago

 

[rotauq]

I know someone who already thinks 100F is too hot to touch

Is there a way to gear down without losing much speed?
That thing is a beast would hate to lose speed

If your motor and batteries are running this hot you will also lose speed. So gearing down doesn't necesairly mean you will lose speed.

 

[SrC]

+1
A great point there.
I don't know why so much speed really matters. +/- 5 mph is not tragic, is it? And what good is Max speed possible if the whole rig goes up in a fireball?
Unless we are talking a dedicated speed runner. Pushing the envelope. The risk being understood and a given.
The K8s is NOT one of them. The 8s line are generally slower overal. After all, it is a large scale 30 pound model with only 8s volts.

 

[LibertyMKiii]

Just bought one five minutes ago

Shoot each wire and connector with the gun also, including motor wires.
You might discover a high resistance point on one of the wires contributing to the heat.

If that is the case you might be able to resolve that instead of gearing down.

 

[SrC]

I know someone who already thinks 100F is too hot to touch

If your motor and batteries are running this hot you will also lose speed. So gearing down doesn't necesairly mean you will lose speed.

Before Temp guns were even a thing, The spit test was used. If your spit sizzled, it was too hot. Not making this up. Im going back 30 years in my RC days....
Imagine drooling some spit all over your rig to test for High temps today.
I never did that. I had a $200. commercial temp gun way back. Ouch. You can buy one so cheap these days.
Mostly for my Nitro engines temps. They needed to be tuned for 200F-212F to run correctly.