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Mamba Monster problem, 6s turns into 5s?
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ruudxd
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Mamba Monster problem, 6s turns into 5s? - 06.07.2015, 09:31 AM

Hello,

I have a strange problem with my Mamba Monster.
I drove in up and down the street yesterday, after a long time, with my new battery.
It did perfect, started up with 6 beeps, so 6S reconized untill it stopped, and I could only steer ( I have a Castle UBEC )
The ESC turned off I think, but the switch was still on the on position.
I turned it of, and then on, and it only gave 5 beeps, so it thought is was a 5S LiPo it think?
Turned it on and of about 5 times, and it still only gave 5 beeps, and the 6th time, it gave 6 beeps again!
But I didn't trust it and stopped driving, and put the LiPo on my Hyperion 0720I Duo3 and it reconized it as a 6S Lipo direct with about 3,5-3,6v per cell.
Now I had this problem last time I drove to, about a half year ago, with a different battery, so I am starting to think that the ESC or the settings are wrong?
I drove a new 6S 4000mah 60C Gens Ace a half year ago, and yesterday I drove a 6S 5000mah 45C Gens Ace LiPo, both where never used before.
Now I have to say that my car was overgeared I think, I used a 23t pinion accidently on a 48t spur on my Losi Muggy with a Traxxas/Castle 1717 1650Kv in it.
Could that be the problem?
The motor was hot ( 70-75c ) the esc was warm ( 40c I think ) and the battery was mid 30s celcius.

Do you know what the problem could be?
And what LVC voltage do you guys use?


Sorry for the long story!

Ruud
   
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Serum
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06.07.2015, 02:36 PM

No, settings are fine; that could be the LVC kicking in, is one of the cells off in your pack? 3.5V per cell is on the low side, that's the voltage for an empty cel. I use 3.4-3.5 as cutoff voltage. Don't know what voltage the MM uses for counting the cells, but if this is set at 4V, it would aim for 24V, so with 6x3.5V the pack measures 21V, which is more or less a fully charged 5S. The controller wil be set around 3.8-4.2 v per cell, and simple divides the measured voltage with these numbers to come to the conclusion that it's either 5 or 6S. The more cells, the harder it will be to determine the amount of cells.

The reason why the last time (6th time of testing) the setup gave 6 beeps again confirms this; if a pack is being drained pretty intense (say, for overgearing or so :) the packs voltage will raise a bit when they are not being used for a few minutes.

If 6S is your standard setup, i wouldn't be using the auto-detect voltage, but just set it to 20.4V fixed.

It's handy to have something like the skyrc 6 in 1 box handy. It can measure the individual voltage of the cells. I always use this on new packs to determine if they are ok.
   
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ruudxd
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06.07.2015, 04:08 PM

Ok, thanks for the info!
I know it divides the total voltage trought the total cell count, but if you say it like so, it makes sense indeed!
I only run 6S ( no nuts, no glory ;) ) so I will set it to a end voltage, that sounds better.

I have one of those 5-10 dollar cell beepers with a little display, could that be good to?
I am thinking of getting an Eagle Tree system, that looks awesome :)

Thanks for the help!

I just checked, the auto cut off was on 3,3v, I have it on 20,4V now, so 3,4V a cell, hope it gets better, I also ordered a new pinion, that should help to :)
   
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BrianG
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06.07.2015, 09:02 PM

Think of it like this: Pretend there is a plain black box in front of you which contains a battery of unknown size and just has a simple set of terminals. You are only told it is a Li battery and given a voltmeter and you have to determine the cell count. So, you measure the voltage, and then based on assumptions about lithium packs (like a healthy cell voltage can vary between 3.0v/cell at near dead to 4.2v fresh off the charger) you make an educated guess of the number of cells. This is basically what an ESC is doing, except an ESC will always assume it is connected to a fresh pack when it is powered up. It doesn't know if you are trying to trick it by hooking a depleted 6s pack, it will just see it as a fresh 5s pack.

And like Serum says, the voltage of a near dead pack will slowly rise back up a little when the load is removed for a while, and may just hit the threshold of what the ESC determines as 6s.
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ruudxd
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06.08.2015, 10:19 AM

Ok, that is a great explanation, thanks!
I have set the Cut off on 20,4 volts now, and I geared down, using your site, wich helps me a lot!


Thanks a lot guys!
   
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