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Old Aug 18, 2012, 01:52 AM
Just flitting about!!
bigroger's Avatar
Joined Aug 2011
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John, I did email you a couple of days ago about 4s4000 packs, didn't hear back.

Are you able to produce to 4s4000 rather than 4s4400?

Looking for as much punch and minimal voltage sag at 85-100A peak loads?
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Old Aug 18, 2012, 02:49 AM
REVOJohn's Avatar
Singapore, Singapore
Joined Apr 2012
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Hi there3 bigroger.
I thought I sent you a reply but we don;;t have a 4000mhr cell. Only 3700 and 4000. Take a look at the specs of the 4S pack on our site and see is she's light enough for you.
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Old Aug 18, 2012, 03:25 AM
Just flitting about!!
bigroger's Avatar
Joined Aug 2011
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John,
better check your ipad mate.

The 4400 you have seems like its 450g which is 30-40g more then I was planning for. As I'll be using 2 in series for 8s.

Is the 60C 4s4400 the same weight as the 40C 4s4400 packs as your web site claims?
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Old Aug 18, 2012, 03:31 AM
Just flitting about!!
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Joined Aug 2011
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Also John,
like you say in your informercial above.

Most of us have heard all the hype and marketing spin from the lipo resellers.

The best way is real life comparisons, eagle tree data from one flight to another comparing one brand to another looking for peak amps, volts sage under load etc.

Everyone can claim they have the best bang for the buck, most fail the performance or they have the performance at the start on a fresh lipo and after a dozen or so cycles it all goes pair shaped and either drops performance, (rising IR) or cells die/puff what ever and its $$ down the drain.

Lets see more real life feedback, love to see some customer testimonials John. Don't care if their heli pilots or fixed wing 3D'ers as long as its real heavy load performance experiences.
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Old Aug 18, 2012, 03:32 AM
REVOJohn's Avatar
Singapore, Singapore
Joined Apr 2012
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Quote:
Originally Posted by bigroger View Post
John,
better check your ipad mate.

The 4400 you have seems like its 450g which is 30-40g more then I was planning for. As I'll be using 2 in series for 8s.

Is the 60C 4s4400 the same weight as the 40C 4s4400 packs as your web site claims?
I'll tell you what I'm doing riiiiiiiiiiiight now today. (tough job)
Is going through all the pack models, prices and updating the new models. I'll check on all the weights for you mate.
Should be updates by Monday
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Old Aug 18, 2012, 04:32 AM
Just flitting about!!
bigroger's Avatar
Joined Aug 2011
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Cheers mate.

I'll probably order a pair of 40C 4s4400 if the weight works out and I'll be able to compare back to back to new Gens Ace 25C4s4000 on this 70" slick 8s setup that can spike to 100A.

That should be a good test.

I'll run it through my eagle tree in the air as well for some real life data.
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Old Aug 18, 2012, 04:40 AM
can't buy vaporware
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United States, MN, Minneapolis
Joined Nov 2011
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Just did some testing with the 3010b charger and the balance board that came with it. For the Revolectrix 60C batteries, the average resistance is 4.3 mOhm per cell. For comparison, I have 7 gens ace 25 c batteries with 20-40 flights on each. The average resistance is 8.5 mOhms per cell.


The Revolectrix batteries have not been flown yet. They were parallel charged/discharged 3 times on the 3010b.

For these measurements, the temperature was 68 degrees, and the packs were either individuall (trial 2) or parallel (trial 1) storage charge.

Last time I was using a paraboard, to take IR, which I think made the measurements less reliable due to an LED on it.

See attached for raw and quickly formated data and simple analysis.

It looks like I have a couple of very good gens ace batteries (1.b and 1.c).

I haven't done this before so I am unsure how these revolectrix cells will measure up after they get a few flights on them.
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Old Aug 18, 2012, 07:18 AM
Just flitting about!!
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INteresting data.

Both the gens and Revo lipo's have much higher IR then I measure with my i206 charger, but mine doesn't have a LED on the parraboard.

I have tried with and without parraboard and got no difference previously, but once again no LED.
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Old Aug 18, 2012, 08:24 AM
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Singapore, Singapore
Joined Apr 2012
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Pretty good results. Our factory specs at 6ohm per cell for the 2200 60C. I'd say you have to get rid of as much cable/connections as you can. Mind you RC hbby chargers measure DC resistance whereas factory IR measurements are taken at AC 1kHz at 50% state of charge
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Old Aug 18, 2012, 10:06 AM
ancora imparo
jj604's Avatar
Melbourne, Australia
Joined Jul 2005
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John, thanks for the insights into the battery industry. They have been very interesting and illuminating. Appreciate you sharing your experience and knowledge.

Just one technical question.

I have never seen any statement about how you take the standard 1kHz impedance IR measurement and turn it into a C rating. Does it rely on an empirical constant value such a the one Mark Forsyth and others have established by careful observation of packs in service or is there an accepted conversion algorithm?

Thanks

John

PS: My Revolectrix packs seem to be getting better with use - hope they keep it up.
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Old Aug 18, 2012, 02:33 PM
can't buy vaporware
7oneWo1f's Avatar
United States, MN, Minneapolis
Joined Nov 2011
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Quote:
Originally Posted by bigroger View Post
INteresting data.

Both the gens and Revo lipo's have much higher IR then I measure with my i206 charger, but mine doesn't have a LED on the parraboard.

I have tried with and without parraboard and got no difference previously, but once again no LED.
The 3010b only reports one significant digit for mOhm. I wouldn't call it a calibrated piece of lab equipment, but it is probably useful for the comparison between batteries.

Also, the table in post #22 was using the 3010b balance board, and not the paraboard with an LED. Another factor that would explain the difference between the results in post #22 and Post #4, aside from the paraboard being used in post #4, is differences in ambient temperature, and less careful connections, and no logging of cell voltages.
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Old Aug 18, 2012, 02:43 PM
can't buy vaporware
7oneWo1f's Avatar
United States, MN, Minneapolis
Joined Nov 2011
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Other comments

Regarding name on label: You're free to do what you want, but I assume you're doing this so you know which pack goes with which order. An order number would probably work just as well. Or a barcode or 2D barcode.

Regarding authentic JST connector and wire harnesses (seems you're implying they are purchased with wires attached), I'm not impressed with authentic if it is not as good as the clone. Solid copper wire, if it is as I assume, will break sooner in use than stranded wire, in my experience.

Regarding customer service and money back gaurentee. That's all fine and dandy. But to this customer (and this isn't directed at you, but all online vendors), the Amazon model is best. Jeff Bezos has said something to the effect that great customer service is when a customer doesn't need to contact Amazon regarding a purchase.

Finally, regarding the load wires' lack of a connector. This not terrible, but I have another idea. I assume your workers are already soldering. Since the packs are being custom built anyway, why not allow an option to have your workers also solder on the battery connector of their choice (e.g., Deans, or in my case, the gens ace HXT 4mm style, or EC5, or whatever other commonly used connectors are out there)?

The problem with the heat shrink on the battery leads is that it can fall off in transit. Low probability of it occuring on any particular order, but if you start selling a lot of batteries, it may turn out badly for some particular order eventually. Your workers, if they are already soldering a lot, can probably do a better job than most end users, and more quickly.
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Old Aug 18, 2012, 03:47 PM
Southern Pride
everydayflyer's Avatar
Haralson County GA. USA
Joined Oct 2004
34,839 Posts
No one uses solid wire for balancing leads. Many use stranded wires with PVC insulation and some use stranded wire with Silicon insulation which is much more flexiable. Most of us prefer the silion insulated balancining leads but I guess it cost a couple of cents more and cost is always an issue it seems.

Even the same vendor will have LiPolys some with PVC insulation balancing leads ansd some with Silicon insulation. One such example is HK 2S Zippy 350 have PVC and Turnigy naotec 370s have Silicon ones.
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Old Aug 18, 2012, 11:03 PM
REVOJohn's Avatar
Singapore, Singapore
Joined Apr 2012
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Quote:
Originally Posted by everydayflyer View Post
No one uses solid wire for balancing leads. Many use stranded wires with PVC insulation and some use stranded wire with Silicon insulation which is much more flexiable. Most of us prefer the silion insulated balancining leads but I guess it cost a couple of cents more and cost is always an issue it seems.

Even the same vendor will have LiPolys some with PVC insulation balancing leads ansd some with Silicon insulation. One such example is HK 2S Zippy 350 have PVC and Turnigy naotec 370s have Silicon ones.
Yah i dont think he meant solid Cu wires. That'd be cupper rods heheheee. I think he was referring to stiffer PVC wires.
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Old Aug 18, 2012, 11:12 PM
REVOJohn's Avatar
Singapore, Singapore
Joined Apr 2012
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Quote:
Originally Posted by jj604 View Post
John, thanks for the insights into the battery industry. They have been very interesting and illuminating. Appreciate you sharing your experience and knowledge.

Just one technical question.

I have never seen any statement about how you take the standard 1kHz impedance IR measurement and turn it into a C rating. Does it rely on an empirical constant value such a the one Mark Forsyth and others have established by careful observation of packs in service or is there an accepted conversion algorithm?

Thanks

John

PS: My Revolectrix packs seem to be getting better with use - hope they keep it up.


Hi there JJ. Glad you are enjoying the LiPOs
As for IR and C rate this is a very interesting question. I'd say there is a direct correlation BUT you probbly could not put a formule too it as there are other parameters at play here.
eg expected cycle life, cell weight, max permissible temperature.
Give you an example. We've built missile battery systems for a country that'll remain disclosed. They requirement was a 7S 15Ahr battery pack with 1500A take off current (and a hugh G force too). Now thats over 100C and we managed to pull it off. But can I claim the bats are 100C. No. I'd say the 1500A could have been repeated mayb 5 - 20 times before that pack died but for this application it was fine. Charge Once......launch once and no return.

So in applying C rate, Capacity, Weight $ in comparisons IR is important but cycle life expectancy is also a factor. Lower the IR and C rate increased as with cycle life too
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