evx2 w/lvc cuts off too early

[bashhound]

I just picked up a Summit for myself and a brushed version erevo for my oldest son. I also picked up 4 5000 mah 35c 2s packs because my Gens ace hard packs wouldn't fit due to the way the wires come off of them. the lvc on the revo seems to trip way early. when i put the packs on the charger they read 7.6v with each cell reading roughly 3.8v each. After recharging they take only about 2000mah per pack...new out of the box they took about 3500mah. Is there a way to manually adjust the cut off voltage on the stock evx2? or would I be better off running a separate lva? can't for the life of me figure out why it is cutting off so early.

Traxxas has a strict language policy. A word filter operates to change inappropriate words and banned websites or brands to *s. When you see these in your post, you MUST edit them out.
-ksb51rl

[zball94]

Does it happen repeatedly or have you only tried once? Sometimes the LVC in my Rustler VXL will trip early, I simply reset it and drive for another 15 minutes uninterrupted.

Also is it cold out where you live? Batteries don't last as long in the cold.

[bashhound]

It is cold, but the summit drains them fine. It has happened in the revo 3 times in a row.

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[Tmaxxed]

This is happening to me on my summit right now. I can plug in 2 fully charged lipos and in 5 minutes or so it hits the lvd. I unplug the lipos, plug them back in and it runs for another 5 minutes or so them hits the lvd again. I did this 3 times and then checked the voltage with a multimeter and it still said 7.4 volts on the 2s lipo. Any ideas why this is happening?

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[alexarizpe]

This started to happen on my slash vxl. It would trip way early so all I would do is turn it off and on again and it would work fine for awhile. I got tired of dealing with it so I order a lva from ebay and been running that way for awhile now with no issues. I think this is a common problem with traxxasa esc's

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[bashhound]

Its very odd to me that one exv2 works fine and the other doesn't. I have 3 other trucks with xl5 escs that have lvcs that work great. Does anyone know if there is a way to manually set the cut off voltage?

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[ksb51rl]

Measuring your packs at rest tells you very little. A resting voltage of 3.7V/cell can equate to a voltage under load of 3.4V/cell or even less. The "early" LVD may not be attributable to a faulty ESC but to different motor amp draws, which is a function of the specs of the motors and the gearing being used (load). It is very possible that your batteries are not up to the particular task required by the Revo's motor system. Cheaper batteries have larger voltage sags under load. But hey- you saved a couple bucks so it MUST have been worth it.

You have two EVX-2 ESC's. Have you swapped them between the vehicles to test the theory of early LVD? If not, why?

There is no way to manually set the LVD for the EVX-2.

[Tmaxxed]

My batteries have worked great in mine for 6 months then just 2 weeks ago this started happening to mine. So its definatly not the batteries.

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[bashhound]

ksb51rl, You make a fair point despite your sarcasm. I haven't swapped them out because I have a career and a kid that wants to play with his brand new truck. As I have never used these particular packs I don't know if they are any good personally, but they have gotten excellent reviews. I apologize for not editing my post I was unaware that i couldn't post a particular brand as it is not in the community rules...I posted another brand and it didn't star it out so I though the language filter had mistaken it for something else. I am not bashing the esc or Traxxas, as a matter of fact all my rc's are Traxxas. i am also not trying to ruffle any feathers. I am just trying to get some insight into the issue. I will pick up a LVA from the LHS in the morning to see if the packs are sagging. I doubt that to be the case as it has kicked in twice at 1/2 throttle and the packs I bought are known for having less sag under load than "premium" batteries.

[ksb51rl]

Ah, nobody thought you were bashing.
Half throttle huh? That may make the diagnosis a bit different.
Some things to consider: worn motors can have greatly decreased efficiency and therefore increased amp draw. This can happen quickly with the stock Titan 550 motors. Larger tires can also increase amp draw, as can any binding in the drivetrain.

As for your batteries, who told you that?

[bashhound]

The motors have had about 5 sets of packs put through them, they were broken in on a large school parking lot up the street. the tires are stock talons. The motors are at 111°F at the end of the run so they don't seem to be overburdened and I can't feel any binding. As for the batteries, just about every independent reviewer on the internet. My thoughts are that if I hook up an LVA and put the esc in Nimh mode I should get a comparable runtime if its the packs sagging. If the run time is considerably longer the esc is at fault. Does that logic seem sound? You said earlier that 3.7 could sag to 3.4 under load...is the LVC in the EVX2 set at 3.4v?

[ksb51rl]

I don't think you need to turn the LVD off to use the LVA. I'd set the alarm at 3.4V/cell and see what happens. Then raise it by 1/10 volt at a time and see where the ESC cuts off. Or you can work your way down. Either way.
I can only estimate the LVD level. I don't believe Traxxas publishes the figure.

[bashhound]

I will give that a shot tomorrow.

[ksb51rl]

I will give that a shot tomorrow.

Best wishes. If the LVD is malfunctioning, I'll tust Traxxas to make it right.

[hottrodd1090]

sooooooooooo whats the results? was it the esc or the batteries? i have had the same issue

[JustinThyme]

My batteries have worked great in mine for 6 months then just 2 weeks ago this started happening to mine. So its definatly not the batteries.

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Because they worked fine for 6 months doesnt mean they arent done now. One bad cell out of the two packs can cause it to cut out prematurely. What you have with no load doesnt tell the true story. Batteries of every type will rebound after a discharge. This is one scenario, another is that the ESC may be malfunctioning and cutting out too soon. If you have a DVM with a min max function you could strap it on and run it until it dies and see what the true min under a discharge condition really was. This will help you make a definitive diagnosis. Also if you have an LVA that will work too.

[bashhound]

Well, the day i was gonna go buy a LVA my son blew both titans on the revo so i ordered a dewalt motor and esc instead. I knew the 550 titans wouldn't last long on lipo anyway. I ran the dewalt and it too lasted less than 10 min. Then I switched the evx2 out for a new one and It solved the problem. I sent the one out of the revo back for a swap so now i have a spare. I have since done the 14.4 dewalt swap to both trucks and I couldn't be more pleased. I get about 45 min run time on the summit with a 21t pinion and about 20 min on the revo with a 31 tooth pinion from KD.

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[hottrodd1090]

ok cool so thanks for the update