Power Warning Help

[janoots2]

Changed out a motor on my hex and took about 3 weeks off of flying due to my job. Stored all my lipos on storage charge at 3.8 per cell.Typically i get 5 1/2 minutes of flight before my first warning and another 30 seconds before my second warning. Today I charged up and took a quick flight and my first warning kicked on about two minutes in and the second about 30 seconds later. Thought maybe my lipo was bad so tried another. Same thing. Tested all voltage and batteries seem to be behaving consistently. Its almost like my settings were changed...Any thoughts on what's goin on?

 

[kloner]

you'd have to know the voltage under a load to completely rulle out the packs sagging like that. Low Internal Resistance packs don't sag as much under a load than some beat up ones.

It was good you stored em right, but without knowing the IR i'd personaly assume there depleting into your LVC settings range.... might not be trashed, but definately apear to be heading in that direction.

Whats the low voltage settings your using? I turned all that off, too risky for where i take em....... it is a crash waiting to happen. i've flown miles on batterys sagging way below there rated voltage. i run along at 50-60 amp draws alot.

 

[janoots2]

My voltage settings are:
First Level: 16.80v - 2.45v = 14.35v LED
Second Level: 16.05v - 2.45 v = 13.60v Descend

When I tested the battery after landing, it read 3.83v on each cell, so it still had plenty of juice.

These are the batteries I run, so they're pretty good quality:
http://www.progressiverc.com/spyder-batteries-black-widow-4s-4000mah-30c.html

Also, they've only been flown for one season, never damaged, always stored at 3.8v, etc., so they were never abused...

I like the idea of the first level LED indicator, but wish the second indicator had an option to just be a red LED rather than automatic descend. Usually if I get that low, I just throttle up anyway to fight the descend and land.

 

[kloner]

the flashing light still happens with it turned off, it just doesn't try to take a dirt nap

What charger do you have?

what it is when you read it on the ground means nothing to what it is in the sky

heres an osd and what a good pack looks like underway. See how when the amps go up the voltage goes down..... thats a pack with IR 3-4mv a cell

saw a 14.2 and thats a 4000 mah pack 1500 mah in

now heres a crappy pack. starts out at rated voltage 1600 mah into 6600 mah total.... by 1:30 it's 5200 into 6600 and 12 volts...... thats a pack with high internal resistance. It's invisible, it's a number a charger like icharger can tell you. it is also seen in voltage checkers to a degree in the form of uneven cell voltages. it'll really start getting different the worse they are. one flight i'll get it 5-8mv a cell, next flight it'll run short on me and i'll take it deeper into hell and that's all she wrote, 2x 3300 4s packs ready for the garbage

they have a normal if everything is perfect life span of 2 years or 200 cycles. if you store them over 40 degrees it'll naturally die off 2-3% a month, if there stored in the fridge, it'll drop to more like .1% a month, if you get em 90 degrees while stored it'll drop 5-20% a month depending on the cells quality. Only thing worse than hot is full voltage and hot. If you have an icharger, look at your manual and read what you got for numbers to me, otherwise call progressive

I do remember something like this as a firmware problem, but it was a firmware that didn't load right or something. I'd look at my packs good and hard first.

those packs in those videos above were all 16.8 when they left the ground

 

[janoots2]

Thanks Kloner, I have a Powerlab 6. I just threw a pack on and checked what the IR and it's bouncing between 2.4 - 2.8 milliohms after about 5 minutes of charging. After about 15 minutes at 90% they leveled out at 2.4, so they are right on the money.

After looking into what my voltage settings should be, it looks like my loss is too high in my values. I never really calibrated it correctly, I just timed voltage usage to get the numbers I needed. Could that be the issue? Weird thing is that it is something new that seemed to change by itself...

 

[janoots2]

I went to the field today for some testing and I have a couple questions/comments I hope someone can help me understand:

1. I believe to have found the the WKM voltage meter inaccurate:

First Level: 14.75 - .4 = 14.35
Second Level: 14.20 - .4 = 13.80

With these settings, my first level comes on around 14.8v and my second level around 14.3 volts. Odd thing is, those are close to my original values, it's almost as if my load is not taken into consideration.

2. This is what I can't figure out: I put on a completely charged 4S at 16.6v. When I take off, my voltage immediately drops to 15.3 -15.6 . So I thought, that is a heck of a loss of 1.3v, right? However, when I landed after my second warning came on at 14.3, and then looked at the voltage, it was at 15.0. So that would also define a loss of .7v right? What one should I believe and why aren't they the same?

My problem is if I put one volt less than the calibrated 16.6v charge at 15.6, the voltage drops below 15.6v when I take off, so it immediately sets off my first level warning, so I can't get an accurate load value. I guest I could double the input value taking 2v off, setting at 14.6 and dividing the loss by two to get a number, right? But that still won't solve my problem...

I conducted 5 flights today all on fully charged batteries and all batteries have IR between 2.4 and 3 milliohms. I never had the is issue before after probably close to 100 flights with the exact same setup and batteries. (2) of the batteries have 30 flights logged, (2) have 15 flights and (1) has (5) flights.

 

[andrewrob]

the flashing light still happens with it turned off, it just doesn't try to take a dirt nap

Hi Kloner
Is this the Wookong M you are talking bout here with voltage protection switched off but still giving the yellow and red strobes? I never knew that was possible!

Thanks

 

[janoots2]

I did some more testing without the voltage monitoring on and didn't have any voltage flashes, just flight mode and GPS lock.

Took voltage readings every minute and logged battery performance.

Learned that packs discharge inconsistently so that explains the varied timing for the yellow flash. However, the voltage/time figures became more consistent toward the end of the discharge.

My end result as of now will be to install an audible voltage alarm and (still) use a timer...like Kloner said

Also, found a great app called RCLogbook with a great timer and tracks battery performance, maintenance and other good stuff.

Was a good exercise and learned a lot on how lipos discharge, especially when you graph the figures. I would suggest doing the same if you have some 'free' time.

Still can't explain why the voltage settings seemed to change by themselves, but doesn't matter anymore since I won't be using it.