Big Rock Big Rock 6s Runtime

[TheGoblinCleaver]

I purchased a new Big Rock 6s with my brothers. We updated the firmware on the ESC. We don't have the nose dive problem, but we are potentially having an issue. We are running it on 2 3s 5200mah lipos and are experiencing very short runtime. Running it only twice, so far, I'd say it was 5-7 minutes. It is relatively cold where I live, at the moment (approximately 45 degrees). That being said, we charged the batteries indoors and didn't allow them to get cold. Is this normal or do we potentially have an issue? To the best of my understanding, it's the LVC, as the truck runs, but slows considerably after 5 minutes or so. The surface was grass/road and we were relatively throttle heavy.
Thanks for your help!

 

[dure16]

Welcome to the forum.

Can you share more info?

What batteries and charger?
Are you sure they’re being charged to 4.2V/cell?
What’s the voltage/cell when it cuts off?
What kind of driving? Full throttle?
Stock electronics?
Stock gearing and tires?

 

[TheGoblinCleaver]

Welcome to the forum.

Can you share more info?

What batteries and charger?
Are you sure they’re being charged to 4.2V/cell?
What’s the voltage/cell when it cuts off?
What kind of driving? Full throttle?
Stock electronics?
Stock gearing and tires?

We did charge them to 4.2v per cell and they are Zee Lipos from Amazon (we've never had issues running them in many, many cars. Everything is stock, in fact this was our first day running it. Charger is Hi Tec X4 AC+ charger. The 3s batteries were at 11.1v after running. Driving it was mostly full throttle the first run and half throttle to maybe 30% full throttle on the second run which was only on the road.

 

[SrC]

That's about right.
I can get 10 minutes on my heavy Fireteam with 6k Mah 6s Cheap AMZ Sypom bricks with a tail wind. The BRCC is about 16+pound heavy, give or take, running weight. Invest in the $30. Smart programmer or use the "set button method" carefully enough to check over ALL your ESC parameters, if you haven't done so yet. Refer to the ESC manual.
Welcome to AF.
When you get the chance, introduce yourself for the official Welcome Committee.

edit.

What exact 5200 mah lipo packs are you running? Specs and all. It's C-Rating? Brand. Colder temps will also reduce the voltage and Amp delivery of most any lipos. Shortening run times. Especially if the packs were cold/chilled when you went to run it. As heavy as all these XLWB 5s rigs are, they need over 6k -7k mah packs with decent C rates to get more than 10 or 12 min run time. Especially on thick grass stuff.

 

[razorrc]

Just lower your LVC. It's adjustable on the Big Rock ESC. Instructions in the manual.

Or you can hook up the programmer again and adjust it there.

 

[KevinC]

Sounds like your individual cell voltage is 3.7 volts when LVC kicks in. There’s still a few more minutes of fun in them tha’r lipos.
As mentioned above, use a program card (or go manual style) and set your LVC one step lower but do keep an eye on your cell voltage……don’t let it run down too low……3.50, 3.55 is my limit personally.

Lipos don’t like low temps, nor does the plastics in RC rigs.

 

[RCbuzz]

If you are noticing the truck has less power and slows down noticeably after 5min it sounds like a battery problem.

I have a couple Zee's as well (older ones that have been good).

But, with alot of these battery manufacturers things can change or be inconsistent. @KnowAir just had to return some Zee's as they were underperforming in a similar scenario you are describing (less than a month old).

Keep in mind resting voltage measured after a run does not indicate what your LVC is. It is an indicator for a healthy battery but the only way to know is what the voltage sag is under load.

Have any other batteries to test?

 

[KnowAir]

Do you have alternate batteries to try? How about trying the batteries in a different rig? Actual running time varies greatly from vehicle to vehicle, as well as surface run on, ect.
Any flashing lights at the esc when it cuts out?
Does it cut out, then run again after sitting for a few seconds?
Many possibilities here..
What voltages are you seeing on the charger after the truck cuts out? Not the most accurate of course as already mentioned, resting voltage is higher than load voltage. But you may be able to see a cell or two that aren't even with the others..which can idicate bad cell(s).