Rivals mt8 losing power

[amoran91]

Hi I have a brand new rivals MT8 running a 7200mah 4S and runs fine heaps of power, Then on full acceleration it slows right down then stops and won't move at all forwards or reverse but I can steer it left and right. If I turn it off and back on works like normal full power then slows down again and stops and I have to walk over and pick it up runs good for about 5 minutes or so sometimes less. Does anyone know what it could be? I'm in Queensland Australia so hot and 32 degrees but rc doesn't seem to feel hot doesn't really run for too long before it stops on me.
Tried re programming the remote still does it Can anyone help? I'm new to the rc thing and not sure what the issue is
Thought battery maybe flat but it appears it fully charged.

 

[WickedFog]

Sounds like you are hitting low voltage cuttoff on your ESC. This could be your ESC LVC is set really high, or your battery has an issue and is suffering from voltage sag. Buy a LiPo alarm and plug it into your battery and run the RC. See what the LiPo alarm says. Set the alarm to go off at like 3.6v.

What does the internal resistance read on each cell at full charge?

 

[jojobeans]

Sounds like voltage sag… battery is probably underspecced for your application, has over exaggerated claims, high IR’s or it’s just wore out. Take a look at the battery testing thread on here, I’d start there. gensacearespammers, CNHL, Liperior, etc make some decent packs.

I’ve had similar issues with common sense Lectron Pro batteries. I’m yet to get one that doesn’t trip the LVC at full throttle.

Apparently this forum doesn’t like the first battery brand I put on there. Did I miss something?

 

[CertifiedMike]

Sounds like voltage sag… battery is probably underspecced for your application, has over exaggerated claims, high IR’s or it’s just wore out. Take a look at the battery testing thread on here, I’d start there. gensacearespammers, CNHL, Liperior, etc make some decent packs.

I’ve had similar issues with common sense Lectron Pro batteries. I’m yet to get one that doesn’t trip the LVC at full throttle.

Apparently this forum doesn’t like the first battery brand I put on there. Did I miss something?

Its a 'feature' added by admin. gensacearespammers
was allowed to post here and decided to spam and try ti take over one day!
This is the story I heard.
Maybe you really did type that and you're psychic?

 

[RustyUs]

Hi I have a brand new rivals MT8 running a 7200mah 4S and runs fine heaps of power, Then on full acceleration it slows right down then stops and won't move at all forwards or reverse but I can steer it left and right. If I turn it off and back on works like normal full power then slows down again and stops and I have to walk over and pick it up runs good for about 5 minutes or so sometimes less. Does anyone know what it could be? I'm in Queensland Australia so hot and 32 degrees but rc doesn't seem to feel hot doesn't really run for too long before it stops on me.
Tried re programming the remote still does it Can anyone help? I'm new to the rc thing and not sure what the issue is
Thought battery maybe flat but it appears it fully charged.

Welcome to RCT.

What does your ESC's LED flash before you turn it off? If it's blinking red, then it's the low voltage cutoff (LVC) that got triggered.

 

[RustyUs]

Having an ESC with non adjustable LVC... sometimes they may be too sensitive, and you are left with what seems to be short run times. Pickup yourself a couple LiPo battery alarms/testers. They should be in everyone's bag of tricks for diagnosing a situation just like this. Turn your ESC's LVC off (NiMh battery mode) and mount one of the alarms onboard your RC's chassis. You can set the LiPo alarm to sound off at your chosen voltage.

 

[amoran91]

Sounds like you are hitting low voltage cuttoff on your ESC. This could be your ESC LVC is set really high, or your battery has an issue and is suffering from voltage sag. Buy a LiPo alarm and plug it into your battery and tun the RC. See what the LiPo alarm says. Set the alarm to go off at like 3.6v.

What does the internal resistance read on each cell at full charge?

Hmm okay I'm not too familiar with these things how do I adjust the lvc? Or how do I test battery? Still working out this charger haha is this battery over charging? Showing 15.3v and slowly climbing its a 14.8v battery

 

[amoran91]

Welcome to RCT.

What does your ESC's LED flash before you turn it off? If it's blinking red, then it's the low voltage cutoff (LVC) that got triggered.

Pretty sure it's blinking red yeah

 

[WickedFog]

Hmm okay I'm not too familiar with these things how do I adjust the lvc? Or how do I test battery? Still working out this charger haha is this battery over charging? Showing 15.3v and slowly climbing its a 14.8v battery

View attachment 214679

A single LiPo cell has a nominal voltage of 3.7v. A fully charged LiPo cell is 4.2v. So a 4s battery will have a nominal voltage of 14.8v. Fully charged it will be 16.8v.

Disclaimer: You absolutely should learn about LiPo charging, care, and safety. Handled properly, they are safe. Improperly, and your house is burned to the ground. LiPo's burn in excess of 3500°F. Enough heat to melt steel if they burn long enough. Not to mention the gasses they put off while burning are super toxic.

There are tons of YT videos out there to help you learn this, as well as Greywolf's LiPo stuff stickied here in the Electronics forum.

I don't believe any charger using that kind of firmware has a way for you to read the internal resistance of your cells. So the only way to know when your battery starts to go bad is when it starts to puff. And that being a hard case LiPo, you won't see that as soon as you would a soft case.

I doubt your IR's are the issue with it being a fairly new battery, but you never know.

Get a LiPo alarm and see what that shows when you run it.

 

[amoran91]

Ahh okay this is showing 3.76v

Okay that's good to know will do thanks for that!

yeah might have to get a lipo alarm see what happens

 

[Lostinthewoods86]

I don’t know the charger, but it looks like you are just balance charging your battery to a storage voltage. Charge the battery to 16.8 volts before you ready to run. We got a mt8, it’s a pretty fun truck .

 

[amoran91]

Yeah charging it up properly now.. I have it on balance charge. It has charge, balance charge and storage charge settings.

Yeah happy with it its a beast of a truck