Turnigy 6S 3000mAh 20C - 30C

[Myken]

Hi all,

I am having some HS issues with my 600E recently. My apologise for a long text

I am using 2x 6S 3000mAh 20C packs in series, I have a total of 8 of them which makes 4 flying packs.
They all have around 40 cycles done.

When I start a heli and bring it to stable hover HS is around 2400 RPM, after ~20 seconds it falls down to 2000 and stays there for a bit longer to start going down to 1800 after 3-4 minutes.

First I had CC ICE HV ESC - thought it might be that, so I have sent it for a replacement and I am using Hobby Wing 70HV atm, but issue remained.

I started thinking it might be LiPo issue, I have checked internal resistance on them and it shows around 7 mOhm across all cells, in my opinion that should be well preforming pack...

As, I ran those batts in the T500 and 600E, I used Deans connectors and splitter for a 600.

Trex500 pulls around 90A in peaks, 600 max recorded was 69A, so I would expect that performance decrease on the 500 will be more noticable than on the 600.

Suprisingly, 500 seems to work just fine and 600 has the "HS drop" issue.

Will you blame the packs or can it be caused by a 1.2 meter(both positive and negative) battery -> ESC 12AWG wire. Will it help if I will reduce the waire lenght to ~40cm?

I am really not keen to buy 8x 3300 packs atm .

Thank you in advance.

Michal

[Nick B]

Cold lipo syndrome perhaps??

How long are your lipos in the cold before you get to your choice flying site?

[NiceBlades]

Michal, Did you look at the cc esc log after your flight to see if you had a problem? I would also bench run with a watt meter as a 12s pack and an edf or something to see if there is a problem. Also is it all packs? I'm not an electrical expert but I would have said 40 cm length rather than 1.2m reduces the potential of a fault/ break in the wire. If this happens on a few lipo's and their all the same try swapping them around until you find the faulty one, if not are the lipo's the same age, if so how old are they? Apologies if you've tried the above already, its just what I'd do, Ian.

[NiceBlades]

Nick, what is the ideal temp to store lipo's? and at what voltage per cell please? Currently mine are at 17 degrees C and about 3.85v per cell for upto 3 weeks at a time (too many Heli's for the time I have available) Many Thanks, Ian.

[Nick B]

Dont know,mine dont get stored to often,if at all.

I know that cold lipos dont perform to well,i take mine up the field in an old cool box with a hot water bottle in side.

[Myken]

Thanks for all those quick replies.

Issue started when it was still relatively warm ~17 C outside. I have not had too many occasions to fly recently that is why I am bringing this up now. I have check IR yesterday. Issue appears on all of the 8 packs. They are around 6 months old.

I know they are only 20C but with this low IR and only ~40A (70A in peaks) load they should be fine imo.

I am just thinking of building more powerfull discharge station than 2 car bulbs to see how voltage will drop under ~40A load, but for that I need someting to be able to pull 1kW of power.... can you thing of anything simple and quiet enough?

[Nick B]

Will you blame the packs or can it be caused by a 1.2 meter(both positive and negative) battery -> ESC 12AWG wire. Will it help if I will reduce the waire lenght to ~40cm?

1.2m..!!???...is that both wires or 2 x wires of 0.6m?

either way thats bloody long,will it effect the performance,i dont know xygax may know,drop him a pm HERE

[ghost2212]

Do you have any way to measure the whole pack IR? I agree with the others that that IR seems ok for a pack of that size. +1 on the castle logs as they can tell you alot though you probably dont have any saved from previously.

Brett

[Myken]

I found some castle logs from November, for me it looks ok, we have tested it with a tacho and that was showing that massive drop in HS and I can actualy hear that. BTW it is 1.2 meter in total including battery wires + connectors.

untitled.JPG

[Si Goodchild]

1.2m sound like quite a lot. The current also seems to be fluctuating a lot, any idea why?

[Myken]

... The current also seems to be fluctuating a lot, any idea why?

I suspect I was not learning flying forward or figure of eight during that flight

[Myken]

Been out today, we had 2x 600EFL Pro with very similar setup and the same throttle/pitch curves.
Mine had 2300 RPM, friends 2700 RPM in hover. I have even shortened wires to ~40cm, but unfortunately it seems that lipos gave up :/.

So I am looking for 8x 6S packs to fit into 500 6s and 600 12S ... can you recommend any without breaking a bank?

Cheers

[sacko]

Turnigy 30c packs from Hobbyking.

If you got the extra though, the Optipower packs are well worth the extra.

[Zeeflyboy]

The best compromise, assuming you can ever find them in stock, are the Gens Ace 25C 3300mah... they are only marginally more expensive than the turnigy choice but everyone raves about how good they are.

They actually have a prototype 3300mah 12S 60C stick that I saw the other day, but I think that won't be available for a couple of months and no idea how much more expensive it will be. http://www.hobbypartz.com/gens60c.html

Optipower are of course a good option if you don't mind the higher upfront expense and like the great UK warranty etc...

[Si Goodchild]

A vote here for TURNIGY 6s 3000MAH 40C packs. They pack a lot of punch and take the punishment in my 500. I always go for the highest C rating I can get.