Battery / Flight time question..

[Grittner]

So, i did a discharge by default my PowerLab 6 was set to 3.3V x Cell, so i did not touch that, i totally discharge the Lipo cells were like this 3.3-3.5-3.5-3.6-3.4-3.6, then i charge it and i put 4073 mAh in, so as Xrayted mention if i use 355 mAh per minute i should get (4073/355) 11:30 minutes with the pack at "0%" but since i should use 80%, ((4073*0.8)/355) 9:15 minutes with the pack at 20% left, so will set the Timer in my TX for 8:20 minutes to be on a safe side, and check if this is correcto.. sounds good.

[helimaddness]

Hi,
Did you take note of what % the PL6 said it was at when the discharge stopped?
You are saying you had .3v difference between the cells on the discharge. This shows you how unstable lipos get at low voltage. Normally at the end of a flight I think mine have maybe max .05v difference at around 3.75v which is as low as I take them.

What they go down to under load is key. Most ESC will have a Low voltage cut off. If the lipo is week you can hit it easy with plenty of unloaded range left. My Trex500 has some 3 year old packs. I got them to hit the Low voltage cut off after 1:30 min of flying. Landed and check was saying 3.95v unloaded. But packs are obviously useless.

So I would take you packs as being 4000 mah total for now. Like you say only budget in using 80% of that. I would not change my timer from 4:30 to 8 min straight up. If its dropping volts under load you might hit the cut off which can be scary to lose 50% power at the wrong time. I would step it up 30 sec a time and keep a close eye on them. If you have a way to log loaded voltage perfect. If not get a cheap lipos alarm that plugs into the balance cable and set it to say 3.5v and see if it goes off before your timer.

Would be interesting to see what real MAH your Pulse packs have.

Also these tests should not be done in parallel. Discharge each pack and full charge on its own. Parallel charging can mask a bad cell in one pack with a good one in the parallel pack.

IR numbers are normally higher on brand new packs. After a few cycles they will come down.

[Grittner]

Originally Posted by helimaddness

Hi,
Did you take note of what % the PL6 said it was at when the discharge stopped?

Yes it was at 6%.

[Grittner]

So in Conclusion Theoretically Speaking.

6s 5000mAh pack.

1.- Uncharging Pack to 0% (PL6 shut´s at 6%) i had to add 4073mAh for a Full Charged Pack.
2.- 80/20 Rule, 4073mAh x 0.80 = 3258mAh is my 80%.
3.- I use 355mAh for 1 minute flying.
4.- 3258mAh / 355mAh = 9.2 minute, i should be able to fly with the 80/20 rule.
5.- Safe side put my timer on TX to 8:30 minute so i have time to maneuver and bring back the Heli.
6.- As i use Kosmik 160 i can program to shut down with the capacity limit option, so i should program with 3500mAh so i can get down without surprise witch is ~1 minute..

[helimaddness]

Originally Posted by Grittner

So in Conclusion Theoretically Speaking.

6s 5000mAh pack.

1.- Uncharging Pack to 0% (PL6 shut´s at 6%) i had to add 4073mAh for a Full Charged Pack.
2.- 80/20 Rule, 4073mAh x 0.80 = 3258mAh is my 80%.
3.- I use 355mAh for 1 minute flying.
4.- 3258mAh / 355mAh = 9.2 minute, i should be able to fly with the 80/20 rule.
5.- Safe side put my timer on TX to 8:30 minute so i have time to maneuver and bring back the Heli.
6.- As i use Kosmik 160 i can program to shut down with the capacity limit option, so i should program with 3500mAh so i can get down without surprise witch is ~1 minute..

6% is about what I get from memory on a full discharge with in couple.
I think in reality you wont get the same results.
The PL6 is maybe only discharging at a few amps. Your heli will be drawing a lot more. 355mah a min sounds low. .355 amp x 60 min = 21.3 amp draw average.check my math on this I might be wrong.

So in reality the voltage drop at 21 amps is going to be a lot more than 3-4 amps the PL6 can achieve. So Things get hotter less efficient, load is higher so voltage drop greater and you will get to your low voltage cut off quicker. I would save allow for .2 to .3 v drop under load.

There is a reason you have a 160 amp esc remember.

I have a 130 amp scorpion with MX750 motor and hovering at low head speed can get 10 min with 25% left. well when lipos were new anyway.

Most people get between 4:30 - 6 min a flight depending on how they fly. I do big air mild 3d and get 6 min now with around 30% left.

I would just be careful doubling you flight times straight up. The voltage alarms are only a few $$ and you can set say .2-.3 v above your ESC low voltage cut off so you get some more warning. They are great for getting in the ball park with flight times. I always use them with a new model until I have it sorted.

http://www.hobbyking.com/hobbyking/s...rm_2s_6s_.html

Cheers

[Grittner]

Will try this weekend and see.

[Grittner]

i had never done before the discharge to 0% and go back to full charge to see capacity of lipo.

1-. Zippy flightmax 5000mAh 45C, I discharge to 6% and put in 4073mAh
2.- Pulse 4500mAh 45C, I discharge to 4% and put in mAh 3829mAh
3.- Revolectrix Dimond 1800mAh 60C, I was really impress at first i though i did something rung but i try with my other pack 6 in total, and i discharge at 3% and on an average i put back 1790mAh almost same as the 100% capacity label.....
how can this be possible.