Granite Granite Mega 4x4 (brushed) with 2s 4000mah lipo, low voltage or heat cutoff?

[SprintFPV]

Hello,

I have some drone experience but new to RC. I bought my kid a Granite 4x4 and we run it with 2s lipos.
We have been driving the car in snow and on icy grass. If we have the car on 100% power the car stops in about 3-5 minutes.
ESC light is blinking and only steering works. If we turn the car off/on it lets you drive again.
How do i know if it is Low voltage or heat cutoff? Should the car start working again if it is because of heat without turning the car off?
If the car has stopped and you turn the car off/on and continue driving with 75% it lets you drive quite long before stopping.
After the car had stopped with 75% i measured the battery voltage to be 7.6V. I usually drain my drone lipos around 3.4V/cell.
Thats quite high voltage for voltage cutoff (7.6V). That's close to 7.7V that i use for storage voltage for 2S lipos.
Do you think we have heat problem? The ESC and motor don't seem that hot after driving. And we have been driving in temperatures from 5celsius to -5celcius.

Sprint

 

[crankestein]

Am not sure if that ESC can do it, but set it to Nicad so there is no voltage cutoff and run it, see if it stops running or when it does it. The only difference between nicad nihm and lipo esc setting is the removal of voltage cutoff and is not limited to any cell count.

 

[woodtoolguy]

Hello,

I have some drone experience but new to RC. I bought my kid a Granite 4x4 and we run it with 2s lipos.
We have been driving the car in snow and on icy grass. If we have the car on 100% power the car stops in about 3-5 minutes.
ESC light is blinking and only steering works. If we turn the car off/on it lets you drive again.
How do i know if it is Low voltage or heat cutoff? Should the car start working again if it is because of heat without turning the car off?
If the car has stopped and you turn the car off/on and continue driving with 75% it lets you drive quite long before stopping.
After the car had stopped with 75% i measured the battery voltage to be 7.6V. I usually drain my drone lipos around 3.4V/cell.
Thats quite high voltage for voltage cutoff (7.6V). That's close to 7.7V that i use for storage voltage for 2S lipos.
Do you think we have heat problem? The ESC and motor don't seem that hot after driving. And we have been driving in temperatures from 5celsius to -5celcius.

Sprint

When the green light on the ESC is flashing, that indicates hi-temp cutoff

When the red light on the ESC is flashing, that indicates low battery voltage (LVC) cutoff


I'm one of those guys who reads every line in the manual after I purchase something.

 

[SprintFPV]

Am not sure if that ESC can do it, but set it to Nicad so there is no voltage cutoff and run it, see if it stops running or when it does it. The only difference between nicad nihm and lipo esc setting is the removal of voltage cutoff and is not limited to any cell count.

Thanks, will try this. If it works over 5 minutes then i know its temp cutoff. Have to be careful not to get over excited and drain my lipo.

 

[Dulb_D]

Thanks, will try this. If it works over 5 minutes then i know its temp cutoff. Have to be careful not to get over excited and drain my lipo.

I would maybe just pick up a cheap low voltage alarm and connect it to the battery, set it to just above where the ESC is supposed to do a LVC. Is this a brushed or BLX? I don't see that mentioned anywhere. If it is BLX, then it is likely your battery doesn't have enough juice for your truck and there are voltage dips when you run it hard and those are triggering this. I had similar symptoms on my Senton BLX and it turned out that (1) my battery was not being charged properly - my charger had a "backup setting" that helped protect against overcharging but that setting was set too low so my battery wasn't being fully charged unbeknownst to me and (2) the battery is labelled as 50c discharge but it seems that calculation is a generous one and so because all batteries (lipo anyway) will experience voltage dips, when this battery dips it's more likely to dip down to the level that will trigger a LVC on the ESC. I tested that using a LVA to confirm. My 75C battery from the same manufacturer does not do this.

 

[SprintFPV]

When the green light on the ESC is flashing, that indicates hi-temp cutoff

When the red light on the ESC is flashing, that indicates low battery voltage (LVC) cutoff


I'm one of those guys who reads every line in the manual after I purchase something.

I have the mega 4x4 granite. I think it has only red led. This is the manual i got https://www.arrma-rc.com/pdf/manuals/MEGA_4X4_ARB10440.pdf
The manual says red led blinking when temp cutoff. Mine is blinking. It doesn't say if light blinks when LVC?

I noticed that with lipo the esc max is 7.4V. I allways charge my 2S lipos to 8.4V.

 

[SprintFPV]

I would maybe just pick up a cheap low voltage alarm and connect it to the battery, set it to just above where the ESC is supposed to do a LVC. Is this a brushed or BLX? I don't see that mentioned anywhere. If it is BLX, then it is likely your battery doesn't have enough juice for your truck and there are voltage dips when you run it hard and those are triggering this. I had similar symptoms on my Senton BLX and it turned out that (1) my battery was not being charged properly - my charger had a "backup setting" that helped protect against overcharging but that setting was set too low so my battery wasn't being fully charged unbeknownst to me and (2) the battery is labelled as 50c discharge but it seems that calculation is a generous one and so because all batteries (lipo anyway) will experience voltage dips, when this battery dips it's more likely to dip down to the level that will trigger a LVC on the ESC. I tested that using a LVA to confirm. My 75C battery from the same manufacturer does not do this.

Thanks. I'ts brushed (i edited the header). Might be a good idea to get the low voltage alarm. Don't remember the C rating of the lipos. Will check that when i get back home.
Manual says low voltage cut off should be at 6.4V. My lipos have allways been over that significally after the car has stopped working. I know there is always bounce back in lipos but not that much.

 

[jondilly1974]

Are you changing the jumper on the ESC to NiMH when you’re not running LiPO? If not, that’s you’re issue.

 

[woodtoolguy]

I have the mega 4x4 granite. I think it has only red led. This is the manual i got https://www.arrma-rc.com/pdf/manuals/MEGA_4X4_ARB10440.pdf
The manual says red led blinking when temp cutoff. Mine is blinking. It doesn't say if light blinks when LVC?

I noticed that with lipo the esc max is 7.4V. I allways charge my 2S lipos to 8.4V.

My apologies, I have the Granite 3SBLX. Different ESC, different programming and user feedback.

 

[SprintFPV]

Are you changing the jumper on the ESC to NiMH when you’re not running LiPO? If not, that’s you’re issue.

Jumper is on lipo.

 

[jondilly1974]

Jumper is on lipo.

If you’re running a NiMH pack, make sure to move the jumper to NiMH. If using a LiPO, make sure to move it to LiPO. Otherwise you won’t be able to use all of your packs safely.

 

[SprintFPV]

This is my lipo

it’s 45c. Just now my kid drove one battery with 50% throttle as long as the car died. Measured the voltage from the battery 7.4v. I will purchase the cheap voltage alarm to check what’s going on. Haven’t tried with nimh setting yet. I’m afraid I will drain the lipo too low.

 

[jondilly1974]

This is my lipo
View attachment 60465
it’s 45c. Just now my kid drove one battery with 50% throttle as long as the car died. Measured the voltage from the battery 7.4v. I will purchase the cheap voltage alarm to check what’s going on. Haven’t tried with nimh setting yet. I’m afraid I will drain the lipo too low.

What are the individual cell voltages of that pack when it shuts down?

 

[SprintFPV]

What are the individual cell voltages of that pack when it shuts down?

The sells where balanced. Both where around 3.7V

 

[jondilly1974]

The sells where balanced. Both where around 3.7V

3.7 is about LVC. Some ESC cut out at 3.8 and others at 3.6. I would guess yours cuts at 3.6 and they rebounded to 3.7. Nothing wrong there.

 

[SprintFPV]

3.7 is about LVC. Some ESC cut out at 3.8 and others at 3.6. I would guess yours cuts at 3.6 and they rebounded to 3.7. Nothing wrong there.

Manual says lvc should be 6.4V? 3.2v is quite low I know. When transmitter is set to 100% we get only 3 max 5 minutes drive time. After that we cancontinue driving with 75% another 5 minutes at least. This got me thinking that it’s the temperature cutoff that kicks in. Got to do little more testing.

 

[SprintFPV]

Just ordered this voltage alarm. I think I can just plug it in the balance lead of my battery while running it?

 

[Cheapbastard]

Manual says lvc should be 6.4V? 3.2v is quite low I know. When transmitter is set to 100% we get only 3 max 5 minutes drive time. After that we cancontinue driving with 75% another 5 minutes at least. This got me thinking that it’s the temperature cutoff that kicks in. Got to do little more testing.

The esc doesn't know the temperature of the motor there is no way it can tell it's the esc itself that can get too hot the thermal cutoff is for the esc. Get a temp gun to get a idea of how hot something is I use this one https://www.harborfreight.com/non-contact-pocket-thermometer-93983.html very useful to have to monitor temps (no finger touch guessing). We can only judge by the heatsink of the esc and the can of the motor but inside could be hotter.

Just ordered this voltage alarm. I think I can just plug it in the balance lead of my battery while running it?
View attachment 60498

Yep just plug it into the balance lead. They have a button to change the voltage you want the alarm to go off.

A temp gun and a lipo alarm can help you determine what maybe the problem overheating or low voltage.

I really think a 60a esc would help because the lower turn (like stock 12t) brushed motors the higher the amp draw and the stock Mega I believe is only a 40a esc.

 

[SprintFPV]

Thanks for your help. I can borrow a temp gun from my work. Any idea when the esc is too hot? If I measure from the cooling element. Will check what amps the current esc is.

 

[jondilly1974]

Manual says lvc should be 6.4V? 3.2v is quite low I know. When transmitter is set to 100% we get only 3 max 5 minutes drive time. After that we cancontinue driving with 75% another 5 minutes at least. This got me thinking that it’s the temperature cutoff that kicks in. Got to do little more testing.

When we talk about LVC, we generalize and talk about per cell, but in reality the ESC can only read total voltage. So you’re right, it’s looking for 6.4vdc. However, you aren’t taking into effect the drop in voltage a lipo has under load. It will sag quite a bit when in use and then rebound. It’s like a rubber band. Never perfectly predictable.