Need help with Naza - faulty VU?

[mitsaras]

Hi,
lately I've been having problems with my quad (Flamewheel 450, Naza+GPS, Jakub 155mm landing gear+gopro+gimbal).
I was getting about 6mins flight with 4S 4000mAh lipo, but I wanted to add FPV Tx and OSD, and my quad apparently became too heavy.
It would start to blink red light and autoland after only a minute or so, and also the VU would intermittently go out entirely, i.e. no orange (Atti) or green (GPS) light at all.
I removed the gopro & gimbal and got back to 8+ mins flight, but again, as the battery goes down to about 3.9V/cell the VU starts acting up again, blinking inconsistently and going out entirely...
Is it possible that my VU has somehow been damaged/overloaded or is faulty in some way? I haven't crashed (...lately!) and all wiring etc. seems OK...

Thanks in advance for any advice!

Dimitris

 

[kloner]

this is what happens as a pack has a high internal resistance, it lets the pack sag under load more than it had previously. Sagging voltage lets low voltage cuttoffs come on....... I'd disable it or drop down the values to let it sag more. your pretty safe letting it hit 3.3v a cell under load as long as it rests back at 3.8, much more than that i'm measuring IR and throwing away packs

 

[mitsaras]

Thanks kloner, I'll check the ir of my lipos...
Any idea why the VU led goes out? is it also because it 'sees' low voltage?

P.S.
the first lipo I checked shows 3.5, 3.7, 2.5, 2.5 mOhm - it was 2.5 on all cells last I checked, no more than 2 or 3 cycles ago.
another shows 5.8, 4.8, 2.9, 2.9...
My batts are Turnigy nano-tech 4S 4000mAh 25-50C, and have less than 12 cycles.

 

[kloner]

the light going out is a bad plug/wire/connection/dead vu

there is some damage showing there. drop the values to like i said and it should be fine, might fly one pack, remeasure ir.... if your really watching the craft to tell you when to land i'd suggest setting a timer on the radio so you can land 30 seconds before that alarm sounds. if you fly the same hover or fff everytime then it'll be consistent in time duration every flight.

 

[mitsaras]

Thank you very much for your help!

 

[hjls3]

mistsaras - might be something to be said for your pack measuring 2.5 on all cells. That is pretty low. 3.7-3.8 mine are either resting or about to get charged. Kloner is certainly the goto lipo guy, but in my limited knowledge - I wonder if you dropped that lipo to low and that is why its giving you problems. Kloner?????

Thanks kloner, I'll check the ir of my lipos...
Any idea why the VU led goes out? is it also because it 'sees' low voltage?

P.S.
the first lipo I checked shows 3.5, 3.7, 2.5, 2.5 mOhm - it was 2.5 on all cells last I checked, no more than 2 or 3 cycles ago.
another shows 5.8, 4.8, 2.9, 2.9...
My batts are Turnigy nano-tech 4S 4000mAh 25-50C, and have less than 12 cycles.

 

[kloner]

those are mili ohms of resistance, not voltages...... know how when you over discharge a pack and the voltage looks different on each cell and it wasn't that way new, that's IR damage. the IR just shows the level of the damage. On mine i'll watch individual cells, but i base my fly/no fly on the total IR at the plug. if it hits 50 mo i'm done with it. they usualy start teens to low 20 for a 40c pack.

 

[hjls3]

AHHHH - gracias grasshopper.

those are mili ohms of resistance, not voltages...... know how when you over discharge a pack and the voltage looks different on each cell and it wasn't that way new, that's IR damage. the IR just shows the level of the damage. On mine i'll watch individual cells, but i base my fly/no fly on the total IR at the plug. if it hits 50 mo i'm done with it. they usualy start teens to low 20 for a 40c pack.

 

[mitsaras]

They were not over-discharged, as when it autolanded the packs measured ~3.85V / cell, but might it have discharged too fast? it went from 4.18~4.19 to 3.85 in about a minute & half...