Unexpected power loss

[bbos12]

I took the XL out today after work and was having a great time until this issue arose.

Driving it on grass when suddenly it loses throttle and rolls to a stop. I give it throttle again and it jumps to life briefly before cutting out again. This persits until I get up to it. I check the battery connections and my other connectors to make sure there isn't anything loose. No dice. Restart the transmitter and still no luck.

So I removed both batteries and notice one puffing a bit (3s SPC batteries) so I hook up the other battery on its own to see if the issue persists. I drive it about 20 feet like this before it seems to lose most of its power (without fully cutting out). Throughout all of this no ESC noises or anything to note. The only thing I've changed lately is binding my new DX4C to the spektrum receiver I had in it before (from a DX2E) but I got 2 brief runs out of it with that setup and had no issues.

Any ideas what might cause this? Everything was running relatively cool. Batteries in transmitter are brand new.

[Burn999]

Simplest to check is what is your low voltage cut off set to on the ESC?

If the cutoff is 3.7v or something like that and the voltage drops then the ESC will cut out. That would be backed up with the time taken for you to mess around with the batteries, figure one is puffed, plug in the second one and drive 20ft. The batteries will have recovered some voltage while you were messing around and then driven a bit until it drops off again.

I set my LVC at 3.3v per cell, some people are paranoid and say its too low, but the cells can drop to 2.8v without damage so I'm still 0.5v over. If you set it too high you only end up using 1/2 the capacity of the battery anyway.

If its not the LVC then try another set of batteries and see what they do.

Only other idea is the motor or ESC thermal cutout but you'd hopefully notice if it got a bit hot!

[VNEMSS]

Is your fan on esc working?? I'd be checking that.

A battery puffed on me just recently, bloody spewing, but it was cutting out on me as well before it stopped completely which still may not be your problem.

[bbos12]

Fan on ESC isn't being used. It's cool enough now that I wasn't worried about it overhearing as I've ran it without the fan in much warmer conditions! I definitely don't think heat is the issue.

Would failing batteries allow the LVC to be triggered even though the batteries are basically fully charged?

I've ran it twice now (after recharging batteries) and it did the same thing. Ran great for 5-10 minutes and then the cutouts


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[bbos12]

Originally Posted by Burn999

Simplest to check is what is your low voltage cut off set to on the ESC?

If the cutoff is 3.7v or something like that and the voltage drops then the ESC will cut out. That would be backed up with the time taken for you to mess around with the batteries, figure one is puffed, plug in the second one and drive 20ft. The batteries will have recovered some voltage while you were messing around and then driven a bit until it drops off again.

I set my LVC at 3.3v per cell, some people are paranoid and say its too low, but the cells can drop to 2.8v without damage so I'm still 0.5v over. If you set it too high you only end up using 1/2 the capacity of the battery anyway.

If its not the LVC then try another set of batteries and see what they do.

Only other idea is the motor or ESC thermal cutout but you'd hopefully notice if it got a bit hot!

Thank you for the reply! I've gotten pretty good at diagnosing mechanical issues but my inexperience definitely shows when it comes to the electronics.

Do you think failing batteries could cause LVC to be prematurely triggered? I haven't altered the LVC at all so unless binding a new TX could have caused an issue. I'll check what my settings are tonight! Thanks again


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[SvdV]

The fan switch could trigger this behavior as well. Switching the fan off mid-run causes the ESC to shutdown, which happened to me a few times. I can imagine that a faulty wire or loose switch can cause what you describe.

[bbos12]

I guess I should have listed electronics!

I'm running the MM2/2200 esc/motor. There's not a switch just for the fan is there? There's the esc power switch but I would think if it was cutting in and out the esc would act like its powering on over and over right?


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[SvdV]

You're right, the switch on the MM2 is to turn the ESC on/off, whereas the MMX switch turns the fan on/off. The switch does indeed trigger the start-up sequence when it is powering, so it looks like this isn't causing your problem.

No idea what else it could be, sorry.

[Lavaheadache]

The switch on the MMX turns the esc on and off, not the fan. I own one.

[84yoda]

Sounds like your battery's are acting up. Are you checking the cells when the power loss happens? Are you still able to drive the rig (after it starts acting up), but wont let you go WOT? Do you have any other battery's to try or can you borrow some to test?

[SvdV]

Originally Posted by Lavaheadache

The switch on the MMX turns the esc on and off, not the fan. I own one.

I own one as well. The manual points to the switch as 'waterproof switch'. Take a look at the diagrams on page 2 and 3.

http://support.castlecreations.com/u...1606201035-446

[bbos12]

Originally Posted by 84yoda

Sounds like your battery's are acting up. Are you checking the cells when the power loss happens? Are you still able to drive the rig (after it starts acting up), but wont let you go WOT? Do you have any other battery's to try or can you borrow some to test?

I have another set I'll give a try! The only thing else I can think of is maybe a receiver issue? I'm thinking it's not an esc issue because it doesn't seem affected when the issue occurs. The only other thing I've changed (besides binding the new DX4C) is that I've been playing with the settings on the transmitter like throttle expo and stuff (trying to figure out its actual effect). I'll try another set of batteries and I'm going to keep the receiver exposed to see if it's cutting in and out when it occurs. Thanks for the suggestion!


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[Burn999]

You could take a multimeter with you and measure the voltage across the cells from the balance ports as soon as it cuts out.

Or try a different set of batteries.

I have some bats with have puffed slightly but give out tons of power, and I believe a certain %age of puffing is to be expected with batteries.

Worth checking to see if your RX has a light on it and if your ESC has lights on when it cuts out, i.e. is everything dead or it still seems powered but the truck just wont move. LVC should trigger the car to stop but the rx, servo etc should stay powered.

Thats a good point, does the steering servo still work?

[bbos12]

Update:
- tried a different set of batteries and same thing happened
- checked the LVC and it wasn't set high but I went ahead and dropped it down to 3.3V just to be sure.
Still trying to figure this one out. I did confirm the last time I took it out that steering still worked when it would cut in/out


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[Lavaheadache]

Originally Posted by SvdV

I own one as well. The manual points to the switch as 'waterproof switch'. Take a look at the diagrams on page 2 and 3.

http://support.castlecreations.com/u...1606201035-446

ya, the switch is waterproof... what's your point? The switch doesn't toggle "waterproof" on and off. It toggles the esc's power on and off.

[Burn999]

Ok so you have found out that as the servo works when its died, there is still power going to the ESC but for some reason its cut out.

I think that the esc is thermalling or cutting out due to low voltage. cant think of any other reason why it would cut out and still provide servo power.

what batteries are you running? are they like 90C or 15C? potentially they cant provide enough juice so the esc cuts out.

did you check the voltage of the batteries when they were cut out? is the esc hot?

[bbos12]

So I think it's a cell issue... One of the cells on both batteries was way below the other two, so it looks like it still had plenty of voltage but I'm assuming the ESC can pick up each individual cell and therefore was shutting off due to the single cell being too low


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[bbos12]

Thank you everyone for the help! I'll report back when I have new batteries and confirm that that was the problem!


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