Granite Abnormally “High” Low Voltage Cutoff on Granite Voltage - 8.0V on LiPo Setting

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IowaBasher

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Arrma RC's
  1. Voltage
I have two Granite Voltages purchased at the same time a couple of months ago. I noticed that one always seemed to run a few minutes more than the other on the same batteries. At first, I chalked it up to different driving styles and assumed my son was driving his “harder” than I was driving mine, but now I have started to collect data that suggests the low voltage cutoff (LVC) on his Granite is different from the LVC on my Granite. Yesterday, we ran both Granites with identical 2S 5200mAh 50c LiPo batteries to LVC (steering would still work, but throttle would not work) and as usual, mine ran significantly longer.

This time, when I put the batteries on the charger (Venom Pro Duo) I took note of the initial voltage. The battery that was in his Granite (that ran a shorter time) was 8.0V (4.0V per cell) and the voltage on the battery from my Granite was 7.6V (3.8V per cell). Both Granites had the battery selector jumper in the LiPo position. I haven’t checked the voltage after running with the 2x Lion 18650 batteries that came with the Granites, but the same run time discrepancy happens with them.

Has anyone else experienced an abnormally “high” LVC on their Granite? Even the LVC of 7.6V (3.8V per cell) on the longer-running Granite still seems high for LiPo that I thought could go down to 7.4V total. The documentation in the manual is so sparse I can’t even figure out the intended LVC for the different battery types...
 
Just a thought...
Another possibility that you could discount by swapping over the escs... is that your sons granite may have a bad gear mesh, bad bearings, tyres full of debris etc.. thats causing it to use a lot higher amperage to go and so hits lvc first with voltage droop... but then it climbs back up to 8v by the time you test it?
 
The shorter running rig has additional load somewhere. Something is binding or shorted. Start swapping parts until you find the culprit.
 
Just a thought...
Another possibility that you could discount by swapping over the escs... is that your sons granite may have a bad gear mesh, bad bearings, tyres full of debris etc.. thats causing it to use a lot higher amperage to go and so hits lvc first with voltage droop... but then it climbs back up to 8v by the time you test it?

Good idea, thanks for the suggestions. I’ll try some swapnostics to see if I can isolate the problem. For reference, what do other people’s 2S LiPos usually read for voltage after a Granite Voltage run where low voltage cutoff was triggered?
The shorter running rig has additional load somewhere. Something is binding or shorted. Start swapping parts until you find the culprit.

Thanks for the suggestion! Two people have suggested this so it is what I will investigate first.
 
Good idea, thanks for the suggestions. I’ll try some swapnostics to see if I can isolate the problem. For reference, what do other people’s 2S LiPos usually read for voltage after a Granite Voltage run where low voltage cutoff was triggered?

I suspect you will get quite a wide range of answers for this question which wont really help you...
Some will be using high C rated Lipos which wont droop half as bad as low C Lipos... not to mention the fact that everyone drives differently, different surfaces etc etc etc. Too many variables..
 
I say that no two identical ECS's run the same. No two lipos/Lions run the same. No two drivers drive the same. I have observed the same, and I don't think too much about it after scrutinizing the obvious possible issues that would need to be addressed.. But yes as stated above, do swap esc's, do check for undue load somewhere in the drivetrain and also consider that RC is not a perfect science. I have also observed what you see:).
 
Have the esc lvc settings been checked?

I haven’t figured out how to check or adjust the LVC settings on the Granite ESC. The documentation in the manual for the Granite has frustratingly little detail. Nothing about LVC or even what the different color and patterns of the ESC lights mean. If anyone has this info I would love to see it!
 
You set the LVC on or off status by changing Variable number one, setting 1 is on (LIPO) and 2 is off (NiMH).

https://www.arrma-rc.com/pdf/manuals/3S_4X4_ARB100020311.pdf

Page 16

Annotation 2020-01-06 001551.png
 
You set the LVC on or off status by changing Variable number one, setting 1 is on (LIPO) and 2 is off (NiMH).

https://www.arrma-rc.com/pdf/manuals/3S_4X4_ARB100020311.pdf

Page 16

View attachment 59822

Good point. The Granite ESC is different from the ESC you referenced, but it does have a jumper to select between Li-ion, NiMH, or LiPo battery type. They call it the “battery mode plug” in the Granite manual. I have always verified that the jumper/plug is in the correct location for the battery type prior to running. I wish there was information about what the LVC setting is for each “battery mode”.
 
Good point. The Granite ESC is different from the ESC you referenced, but it does have a jumper to select between Li-ion, NiMH, or LiPo battery type. They call it the “battery mode plug” in the Granite manual. I have always verified that the jumper/plug is in the correct location for the battery type prior to running. I wish there was information about what the LVC setting is for each “battery mode”.
Poop I missed the Voltage in the header.
 
Just had the same problem with my voltage ESC. If you asked me, it’s a piece of poop. I’m looking to upgrade and pair with with my GoolRC 13T Brushed. Still researching what I should go with.

I’m not ready for a brushless upgrade just yet but when I do it’ll be something decent.
 
@IowaBasher Have you learned anything else?

I just had a pair of LiPOs show up from Amazon, but I'm experiencing the same thing as both your truck and your son's truck. My LVC kicks at 7.9V! I too purchased 2s 50C 5500 mAh batteries. I get to run for less than two minutes then the truck slams the brakes and stops. The steering still works, but the light on the ESC blinks.

I eliminated the possibility of the ESC shut down due over heating. To do this I moved the shorting plug over to the NiMH Battery Position on the ESC, and ran the truck on a timer to be sure I don't over draw from the battery. The truck never stopped and I finished the timer without incidence. After running for 5 minutes on a timer the motor and ESC were cool to the touch. I then measured the voltage to be 7.4V, a difference of 500mV from starting my measured run. I thought this was also surprisingly fast, drop but who knows. I'm pretty new to RC.

My truck came with a 7.2V 1800 mAh NiMH pack which runs for roughly 15 minutes, so I thought if I upgrade to 5500 mAh I would get better than 30 minutes of run time. I'm sure you can imagine my frustration. I don't even see the point to use LiPo if I'm losing capability.

Does anyone more experienced than me have any suggestions? I plan on reaching out to Arrma but I wanted to gather knowledge from here first.
 
There is something wrong with the cut-off voltage, no matter your drive style or binding, that is just on top of it. A LiPo battery is considered empty when it reaches 3.7V which roughly translates to 90% of the capacity being used up. This is when no load is applied, granted it might recover to 3.75V to 3.8V after a couple minutes. At 4V(per cell, 8V for 2S) you have barely used up 10%, see table at the link.
No idea what your ESC is doing, a cheap fix is to switch to NiMH mode, like you did, but get a voltage alarm and set that to the 3.7V level. When it beeps you know you are at end of battery life. Only difference for the ESC is the LV trigger level, in NiMH mode you have no protection against extreme discharge and resulting lipo damage but there is no other 'magic' happening within the ESC.

Voltage vs levels, don't take it as gospel, values vary but only slightly.
https://www.powerstream.com/lithium-ion-charge-voltage.htm

Cheap fix: NiMH moda and alarms like this: they can falsely trigger when you punch but you get used to it
https://www.amazon.com/CAMWAY-Batte...=2025&creative=165953&creativeASIN=B07DC3LH9C
or
with some that will truly trigger at the right level:
https://www.smc-racing.net/index.php?route=product/product&product_id=559
In both cases you need to set their levels to 3.7V and bash away until it consistently beeps. The cheap version might beep early but reset itself after couple beeps if it was just a punch trigger.

More expensive fix: New ESC
Best solution: get a new ESC with a new truck ;)

Edit: Reach out to Arrma, maybe this is something under warranty.

Hope it helps!
 
It’s likely your lipo isn’t really a 50C output as claimed. When your lipo can’t deliver the amps promised the voltage will sag and the LVC will kick in. If your lipo WAS capable of at least 35C (minimum recommend) then the voltage would not sag and you could avoid LVC. Buy yourself a LiPO alarm and run in NiMH mode. You will either confirm or deny my hypothesis. Set the LiPO alarm for 3.6v.

Also, when discussing your voltages, you always want to refer to it on a per cell basis. It avoids others from having to do the math not knowing how many cells you are running.
 
There is something wrong with the cut-off voltage, no matter your drive style or binding, that is just on top of it. A LiPo battery is considered empty when it reaches 3.7V which roughly translates to 90% of the capacity being used up. This is when no load is applied, granted it might recover to 3.75V to 3.8V after a couple minutes. At 4V(per cell, 8V for 2S) you have barely used up 10%, see table at the link.
No idea what your ESC is doing, a cheap fix is to switch to NiMH mode, like you did, but get a voltage alarm and set that to the 3.7V level. When it beeps you know you are at end of battery life. Only difference for the ESC is the LV trigger level, in NiMH mode you have no protection against extreme discharge and resulting lipo damage but there is no other 'magic' happening within the ESC.

Voltage vs levels, don't take it as gospel, values vary but only slightly.
https://www.powerstream.com/lithium-ion-charge-voltage.htm

Cheap fix: NiMH moda and alarms like this: they can falsely trigger when you punch but you get used to it
https://www.amazon.com/CAMWAY-Batte...=2025&creative=165953&creativeASIN=B07DC3LH9C
or
with some that will truly trigger at the right level:
https://www.smc-racing.net/index.php?route=product/product&product_id=559
In both cases you need to set their levels to 3.7V and bash away until it consistently beeps. The cheap version might beep early but reset itself after couple beeps if it was just a punch trigger.

More expensive fix: New ESC
Best solution: get a new ESC with a new truck ;)

Edit: Reach out to Arrma, maybe this is something under warranty.

Hope it helps!

Thanks for the suggestions I'll do some more digging.

when discussing your voltages, you always want to refer to it on a per cell basis. It avoids others from having to do the math not knowing how many cells you are running.

Copy all.

It’s likely your lipo isn’t really a 50C output as claimed. When your lipo can’t deliver the amps promised the voltage will sag and the LVC will kick in. If your lipo WAS capable of at least 35C (minimum recommend) then the voltage would not sag and you could avoid LVC. Buy yourself a LiPO alarm and run in NiMH mode. You will either confirm or deny my hypothesis. Set the LiPO alarm for 3.6v.

The LiPo was purchased on Amazon. The battery could easily be some counterfeit garbage. Thanks for the help.
 
Last edited:
Thanks for the suggestions I'll do some more digging.



Copy all.



Great thinking. I could see this being very true, the LiPo was purchased on Amazon, the battery could easily be some counterfeit garbage.
To be fair, all lipos lie about C ratings. ✌?
 
The LiPo was purchased on Amazon. The battery could easily be some counterfeit garbage. Thanks for the help.

I doubt it's your lipo (not saying that it can't be). The C rate doesn't need to be high for a brushed 20t (stock Voltage motor) motor or for most brushed motors for that matter. Get a lipo alarm as suggested since it's a brushed motor I would set it at 3.4v and give it another run.
 
I doubt it's your lipo (not saying that it can't be). The C rate doesn't need to be high for a brushed 20t (stock Voltage motor) motor or for most brushed motors for that matter. Get a lipo alarm as suggested since it's a brushed motor I would set it at 3.4v and give it another run.
Thank you Sir. Will do.
 
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