Lipo issues

[Yoldume]

just took my buggy out and all was well for about a minute until all the power went and it was coasting around as if i was running a flat nimh pack,

so i walked home and plugged it into my charger and it read 7.96v my charger takes it to 8.4v (is this correct ?) so if it was nearly fully charged whats gone wrong ?

and tbh i think my charger is innacurate because when i fit my lipo monitor readout to it it mainly reads a different of -0.6 to what the charger is telling me

and i also think my lipo cut off in my esc is turd it cuts off at 3.0v per cell and ive checked it after a run and s1 was 3.19v ans s2 was 3.23v

also when i balance theres useually a +/- OF 0.4v

is this all normal or could this be why my pack is acting funny ?

cheers

[DCM]

what esc do you have?

[Yoldume]

Dont laugh its a orion vortex 70a i bought on the cheap cos my MM had a blue smoke moment a few weeks ago

[Marvin]

Check your motor as your batteries sound fine.

The motor's rotor could have broken up (the magnets slipped off the shaft or similar). That would explain the sluggish performance - I've had it happen to me on my 1/8 scale stuff.

[Yoldume]

i did think this it cogs on takeoff and give half performance,

there is alot of heat i think somewhere along the setup theres a gearing and resistance issue

lipo is a headache

[petemid8]

just took my buggy out and all was well for about a minute until all the power went and it was coasting around as if i was running a flat nimh pack,

so i walked home and plugged it into my charger and it read 7.96v my charger takes it to 8.4v (is this correct ?) so if it was nearly fully charged whats gone wrong ?


I bought a used lipo off ebay and after a few runs it did exactly what yours did. I've tried to revive it but it looks like one of the 2 cells is goosed so I am going to bin it.

Did you get your lipo new? Is it possible it could have been discharged too much at some point? If it's fully charged and not performing it doesn't look good, hope I'm wrong!

[Yoldume]

well i did have an issue with my charger on its third charge when i had a powervut while charging i started the balance charge again and it never said full or finished the charge

the first charge was 40 mins and took 3400mah and the second was 50mins and reached 2550 and i stopped it because it was getting worrying

[petemid8]

The charge current does slow right down towards the end of the charge so I wouldn't worry too much about that.

Does your Orion Vortex ESC really have a lipo cut off? If not you might have discharged your lipo too much unfortunately

[Yoldume]

get the impression this might be the case

i think a new lipo and a novak smartstop might be the way forwards

[Marvin]

Check the motor first! This could be the cause of all the heat and the problem. I've had rotor issues with my Tekin T8, always the same when they fail: I suddenly get a lack of any torque or bottom end power.

[Yoldume]

ok if it isnt this issue am i safe to assume its the battery ?

the motor isnt rebuildable its a MM 5700kv sensorless

[DCM]

I would be interested in the ESC setup, and what the voltage cut-off is set to, thats first port of call.

[Big G]

what C rating is this battery pack?

[Marvin]

Have you got another motor to put in there? I would give that a try if you can.

As Big G says, what packs are you using, what is the continuous discharge, and what capacity are they?

[Lowie]

it's normal that an ESC kicks the Voltage Cutout in when voltage drops .. and it's completely normal that after picking up your car, the Battery-cells read out more then the 3V per cel.
When under tention the voltage drops. But when the pack is left to recover a bit, the voltage goes back up again. Not much, but from 3V till 3.2V is normal.

[Yoldume]

its a turnigy 5000mah 20-30c 2s pack its a week old

no i havent got another motor

and the cutoff is 3.0v per cell

its not gone below 3.0v per cell

on thing i have noticed is when the motor cog's it wont move if the wheels are being turned

is this an issue with the esc ?

[Big G]

if the 'cog' aka pinion won't turn on the motor there's your problem

the motor should spin freely all the time not like a servo that centres itself while powered up.

I've run my lipo cut off at 3v/cell and that works fine. when I tested a pack that had cut out it was showing 6.3v. didn't test each cell though, but they are generally the same since I balance charge them more often than not and the packs are a few months old

[Yoldume]

sorry i mean it judders before it sets off cog's

itsas if its not getting anough juice from the battery to pop a wheely like normal

[Big G]

just to clear it all up.

if you move the motor so it's no longer meshed with the spur does the car free wheel?

can you turn the motor by hand without any effort?

does the car drive properly with another battery pack?

[Yoldume]

yes the var spins freely done all this last night stripped and cleaned and the motor spins freely for atleast 20secs

i havent tried another battery pack im at uni and thats where my stuff is and my nimhs are there i only have 1 lipo

i will do this when i get home later

so to clarify my symptoms are:

a fully charged lipo last about a minute before it goes flat but sill reads around 7.5v

cogging or juddering when i hit the throttle