Very dissapointed

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trout74

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im an ARRMA fan boy through and thourgh. I have 2 kratons and 2 outcasts all modded to the gills, and a youtube channel to back it up ( trout74) . I bought a granite 4X4 mega for my 7 year old to play along with me. Totally stock running a 2S lipo. First pack an 8000mah 2s lipo and it thermal shutdown in 15 minutes. let it cool off and 15 minutes later thermal again. Very dissapointed. First time ARRMA really pissed me off. I have to buy a real ESC to run a stock brushed motor???? SERIOUSLY? ARRMA this is terrible.
TROUT
 

GuyFromCanada

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im an ARRMA fan boy through and thourgh. I have 2 kratons and 2 outcasts all modded to the gills, and a youtube channel to back it up ( trout74) . I bought a granite 4X4 mega for my 7 year old to play along with me. Totally stock running a 2S lipo. First pack an 8000mah 2s lipo and it thermal shutdown in 15 minutes. let it cool off and 15 minutes later thermal again. Very dissapointed. First time ARRMA really pissed me off. I have to buy a real ESC to run a stock brushed motor???? SERIOUSLY? ARRMA this is terrible.
TROUT
FWIW, I run 5300mA NiMH packs through my Granite's, and the motors have gone before the ESC...maybe the heat sink is poorly attached?
 
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trout74

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I ended up installing a Castle Sidewinder3 and 4500KV sensored green motor. Life is good. Used stock 14T pinion, so its not really much faster, just way more efficient.
Trout
 

GuyFromCanada

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I ended up installing a Castle Sidewinder3 and 4500KV sensored green motor. Life is good. Used stock 14T pinion, so its not really much faster, just way more efficient.
Trout
I'm interested in the same idea...is it the SCT version? Did you consider the 3800kV motor?
 
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trout74

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3800 would be fine too, its the sensored one, I had it on hand. So I just popped it in.
Trout
 
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trout74

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yeah it woke it up a bit. Could go up a few in Pinion and get some good speed, but its for my 6 1/2 year old, so hes good.
Trout
 

ThatDrewGuy

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Would a good motor fan solve that problem you think? They are cheap, but made a significant difference (30 degrees) on both my Talion, and Typhon. I was running 190-200, and took it down to 165 which seems like a sweet spot for the 90+ weather I’m currently running them in.
 

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When I was running the stock power system, I had the same issue - about 15 minutes in, the ESC would thermal, right at 175f. The motor would be around 190f-205f. Stock, neither the motor or ESC has a fan, and the ESC heat sink is kind of shallow. Fans might help the situation, but...

I am not sure what Arrma should have done to fix the situation. 91/14 is already pretty low gearing, and a 550 /12t is about the most power you can get (cheaply) out of a brushed motor.

For sure, the Mega 4x4 platform just begs for a brushless system. And a better diff input. The rest of the truck is solid. If/When Arrma releases that version, it will be a killer truck!
 

Bri26

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Do you think the electronics aren't getting good airflow with the tall chassis dirt guards in the front?

Best regards,
Brian
 

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Maybe less airflow than without the guards, but I suspect that even if the guards were removed, you would still have heat issues. A fan on the ESC and motor would also help, but the ESC and motor would still be overworked. The truck just needs more power than you can get from a brushed motor. Or it needs lower gearing.
 
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trout74

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Agreed. It needs brushless setup and better esc. We’re many many packs in on 2s and we’re good to go.
 

Jfpryde

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I don't know that many entry level brushed rigs do any better. I had similar issues with ECX brushed stuff and my older rustler until I upgraded to the beefiest brushed esc I could find. I woulda just gone brushless on that one if it weren't for my kiddo. I didn't want him to have too much power.
 

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If you don't want too much power, but are tired of burning up brushed motors, look into one of the "F540" motors - they are 380L (long) brushless motors, with big cooling fins. Power is similar to the 12t 550 motor in our Granite mega 4x4. I ran one in my Mega 4x4 for a few batteries, it worked well, and kept the speed similar to stock.

The motor I have is a Racerstar, but there are a lot of different ones out there... Here is a longer write up I did on my F540-
https://www.rcgroups.com/forums/showthread.php?2713040-Racerstar-F540-45A-ESC-combo-Review
 

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This will seem like a dumb question, but are we certain it is a thermal thing? I thought mine was going into thermal shut down, but I now believe it may be just an overly conservative LVC? Mine "thermaled" again today while running in the grass (90-ish degrees, sunny, running in fresh cut grass, all stock and running a Zippy 3000mah, 2S, 30-60C LiPo). I left my temp gun inside, but. I could feel heat through the chassis while holding the truck (where the motor is), and could feel heat rising up off the heat sink on the ESC. I unplugged everything and let it cool down for over an hour (inside in the AC). Leaving the same battery in there, I plugged it all up and threw it back in the grass. My monitor (I always run an external voltage meter for redundancy) beeped once, the truck ran about thirty feet, then it stopped again. Red blinky light at the ESC, but with ZERO HEAT. When I charged the battery it ended up taking over 2000mah, and it's a 3000mah pack.

My point being that maybe it's less a heat thing, and more an overly conservative LVC thing? I didn't think to check the charge level of the individual cells when I plugged it into my charger (should have done that!), so I don't really know how low either cell got. Next time it "thermals," I will shove a fresh battery in there and see if it will keep going. That should answer weather or not it is heat or LVC. I watched a YouTube vid of a guy running all stock on 3S, until the motor almost burned-up! If the thermal cut-off circuit was as sensitive as it appears, wouldn't that guy's car have shut down LONG BEFORE motor melt-down (especially on 3S)?!?
 

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Well, the temp sensor is in the ESC, not the motor. The ESC shuts down at 175f per the manual, and that is exactly what I saw in the field. Let it cool off a few minutes, and then run some more, and again shutdown right at 175. At each shutdown, the motor was around 195-210f. I considered adding a fan to the ESC, but then the motor would just keep heating.

I did try to swap in a fresh lipo - the first was only at 3.9 per cell, so that would be a long way from LVC. The second got about 30 seconds before shutdown. Second lipo was now around 4.18 or so...
 
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I just bought my daughter a senton 4x4 mega and was running some of my older 2S lipos and thought it was hitting the thermal shutdown as well. The book doesn't say what it does for the LVC but does show the red light blinks for thermal. well it was blinking so I figured thats what it was but everything was cool so I thought it was faulty, tried another battery in a while and only got a few minutes before it shut off again. So I pulled out one of my newer batteries and had no problem. so while some people might hit the thermal my issue is that the LVC is too aggressive in my opinion. Nice thing about my hobbywing and hobbyking ESCs is that they have a soft cut first, so after a few minutes the voltage might dip on a WOT run, it slows down but then recovers when the battery isn't under that load and I can drive it back to me. It's helping me get the end of the life out of my oldest lipos where they would already be trash if the arrma was the only RC I had. Plus when it hits cutoff its done and I have to walk to where ever it is to get it.
 

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Yesterday I ran one of my newest batteries in the Granite first, for about ten minutes, while testing a brushless system in it. Then I ran the same battery for about 5 minutes after putting that same brushless system back in my Slash. After I reinstalled the stock brushed system in the Granite, I put that same battery back in it to make sure All was well. The truck went half way across the yard and stopped, with the “thermal” light flashing. Everything was completely cool to the touch, the car just wouldn’t move under power (still had steering, of course). Fresh batt: truck runs fine. According to my charger, the first battery was reading at 3.57v per cell?!? So it seems MY esc has an lvc set at 3.6v per cell. I don’t remember what it’s supposed to be rated at, but I doubt it should be that high?
 

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This sounds good to me.

Having the battery resting at 3.5vps - 3.6vps is a good place to stop. That is about 90% drained, and high enough you should not have to worry about a cell going below the 3.0v danger zone.
 

Mentolio

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Yeah, I guess in retrospect it's not so much ridiculous as it is safe. Many other systems offer the option of 3.0 (too low), 3.2 (what I've always used), and up from there. I always use an external lithium voltage monitor/alarm, which I believe is set at 3.2 or 3.4 volts (when the piezo horn sounds).
 

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