Granite Anyone running 2S in their 3S?

[Arrmature]

I have a Granite that has always triggered LVC at 6.15V or so running 2S (less then 3.1 V per cell). I contacted Horizon Hobby and they sent me a new ESC, but I have the same problem. Before receiving the replacement ESC, I bought a Typhon, and it has the same issue, LVC less than 6.2V on 2S.

Horizon Hobby is now sending yet another ESC and a radio (not sure why - the radios in both have been replaced). It seems to me there is a design issue with the LVC on 2S, but I can't seem to get anything out of Horizon Hobby other than "let's try another one".

If anyone else runs 2S in these rigs, what is your battery voltage at cutoff? It looks to me like they may have a firmware issue, but it would be nice to know what others are seeing.

Thanks.

 

[NewSensei]

I had a similar problem when running 3s on my senton and I had put a 120 amp esc with a 4300kv motor in it, turns out it was the connectors I was using. They were too small so I converted all my RC to use XT90 connectors and the senton runs without issue now. Apparently having too much impedance through those connectors can trick the receiver in to believing the battery is drained because it can't pull the power it needs.

If you're having failure after failure it might be worth checking. That said, if you are running 2s and having this issue it's probably not the connector. TBH I only ran the stock mega for a few months before upping it to a brushless but never had a lot of issues with the stock stuff on 2s brushed, was just a tad under powered for my liking
I initially used this on 2s and it screams compared to stock:

https://www.amazon.com/gp/aw/d/B07WHCM3Y2/ref=ppx_yo_mob_b_inactive_ship_o1_img?ie=UTF8&psc=1

Then I upgraded the esc because I wanted more power (of course) to this:

https://www.amazon.com/gp/aw/d/B07WHCLTYQ/ref=ppx_yo_mob_b_track_package_o0_img?ie=UTF8&psc=1

 

[Arrmature]

My batteries al have either EC5 or IC5 connectors, so that's likely not the issue. I'm measuring the battery voltage at about 6.15-6.20 volts under no load right after LVC kicks in. If I let the batteries sit for an hour or so, the voltage recovers to about 6.40. It's just way too low.

 

[NewSensei]

My batteries al have either EC5 or IC5 connectors, so that's likely not the issue. I'm measuring the battery voltage at about 6.15-6.20 volts under no load right after LVC kicks in. If I let the batteries sit for an hour or so, the voltage recovers to about 6.40. It's just way too low.

EC5 is not an issue but I was talking about smaller connectors such as deans.

 

[Yonic]

How hard do you drive the cars? do you run on 100% and reach full throttle? or is it a gentle drive?

LVC is not that simple. lipo drop voltage considerably under load. a lipo with 50% charge will drop to 3v under hard acceleration,

so if you plan to drive hard, an LVC set to 3v will result an LVC that trigger at around 3.6 if driven hard, but if you only drive very gently, it will trigger close to 3v, which is not good.

on the other hand LVC that is set to cut at 3.6, will be good for gentle driving, but will cut at 3.9 with hard driving.

(the numbers i wrote are approximation, alot of parameters can effect that, like the specific lipo and what is "hard load" etc)

 

[nino]

Yeah, LVC is all kinds of messed up in 3s Arrmas. Get an adjustable lipo alarm and you solved your problem for a couple of bucks.

 

[Yonic]

I don't think it's messed up in the 3s. the LVC in the blx185 for instance was always set low to 3.2, which is ok since people with that car are mostly driving pretty hard. but the 3s cars are owned by a greater variety of drivers, so Arrma seems to move between low & high LVC setting on the firmware, it would be simplest if they open the firmware so the user can choose it.

 

[Grimbles]

One further though on this - have you checked the lvc setting using a program card? Plugged my hobbywing program card into my buddy's stock typhon 3s esc and its lvc was set to nimh (or off, cant rememeber) out of the factory. 2 mins later this was solved using the program card, setting the lvc to one of the lipo settings.

 

[Arrmature]

How hard do you drive the cars? do you run on 100% and reach full throttle? or is it a gentle drive?

LVC is not that simple. lipo drop voltage considerably under load. a lipo with 50% charge will drop to 3v under hard acceleration,

so if you plan to drive hard, an LVC set to 3v will result an LVC that trigger at around 3.6 if driven hard, but if you only drive very gently, it will trigger close to 3v, which is not good.

on the other hand LVC that is set to cut at 3.6, will be good for gentle driving, but will cut at 3.9 with hard driving.

(the numbers i wrote are approximation, alot of parameters can effect that, like the specific lipo and what is "hard load" etc)

Sometimes I'm driving under full throttle, other times not. The battery voltage is always the same at LVC at under 3.1V per cell with no load. I would have thought that the firmware would look at both voltage and current when deciding when to trigger the LVC. You're right at higher currents a battery's voltage at the terminals would be lower than at lower currents. I did run once with a voltmeter attached to the battery and checked the voltage every 30 seconds or so. At one point, the battery voltage was about 7.1 (3.55/cell) and 30 seconds later it was down to 6.15 (3.07/cell).

One further though on this - have you checked the lvc setting using a program card? Plugged my hobbywing program card into my buddy's stock typhon 3s esc and its lvc was set to nimh (or off, cant rememeber) out of the factory. 2 mins later this was solved using the program card, setting the lvc to one of the lipo settings.

I had considered that possibility. I don't have a program card, but they both seem to be set to Lipo mode. Just to be sure, I ran them both with a fully charged 7-cell NiMH battery and didn't get more than 10-15 seconds of run time before the cars hit limp mode.

Yeah, LVC is all kinds of messed up in 3s Arrmas. Get an adjustable lipo alarm and you solved your problem for a couple of bucks.

That's exactly what I've been doing, but the alarm upsets my son. I probably shouldn't have explained to him the dangers of over-discharging a lipo. I was hoping that Horizon would have a solution. I'm also looking at installing external BECs to feed my power hungry servos, so I'm going to be running short of real estate, especially in the Granite.

 

[Grimbles]

I don't have a program card

They're cheap as chips mate. The bog standard hobbywing ones are sub £10 in the UK and work - just make sure you check the settings codes in the manual as the ones printed on the hobbywing card don't correspond to the arrma escs. I think spending the tenner is worth being in control of your discharge voltages

https://wheelspinmodels.co.uk/i/264679/

 

[Arrmature]

They're cheap as chips mate. The bog standard hobbywing ones are sub £10 in the UK and work - just make sure you check the settings codes in the manual as the ones printed on the hobbywing card don't correspond to the arrma escs. I think spending the tenner is worth being in control of your discharge voltages

These cards aren't really necessary - the ESC will tell you the setting through a series of flashing LEDs. Having said that my local hobby shop sells the Hobbywing program cards pretty cheap so I may just pick one up. They're $13.99 Canadian so about 8 quid.

 

[Grimbles]

These cards aren't really necessary - the ESC will tell you the setting through a series of flashing LEDs. Having said that my local hobby shop sells the Hobbywing program cards pretty cheap so I may just pick one up. They're $13.99 Canadian so about 8 quid.

Agree with that but they do make life easier

 

[tygger420]

Im not sure if this helps i bought a arrma granite mega and when running in Lipo mode my LVC is 6.7 constant ,which isnt bad but i would be happy at more like 6.4 feels lacking.

 

[Arrmature]

Im not sure if this helps i bought a arrma granite mega and when running in Lipo mode my LVC is 6.7 constant ,which isnt bad but i would be happy at more like 6.4 feels lacking.

I'd take 6.7 in a heartbeat over what I have.

 

[tygger420]

I'd take 6.7 in a heartbeat over what I have.

Agree 100%