Wattflyer RC Network: RC Universe :: RCU Magazine :: RCU Forums :: RCU Classifieds :: RCU User Reviews :: RCU YouTube
Home Who's Online Calendar Today's Posts RealTime Post Spy Mark Forums Read
Go Back   WattFlyer RC Electric Flight Forums - Discuss radio control eflight > Electric R/C Airplanes > General Electric Discussions
Register Members List Wattflyer Extras Articles Search Today's Posts Mark Forums Read Social Groups

General Electric Discussions Talk about topics related to e-powered RC flying

Thank you for your support (hide ads)
Reply
 
Thread Tools Display Modes
Old 04-19-2014, 04:18 AM   #1
garyp1029
Member
 
Join Date: Mar 2014
Posts: 73
Thanked 0 Times in 0 Posts
iTrader: (0)
Friends: (0)
Default C Discharge????

I have read "Everything you Want To Know . . ." as well as several other posts concerning C discharge and I still don't get it. I understand that C is a discharge rate of drawing a certain quantity in a specified time period, BUT EXACTLY HOW does it affect real life choices? Using a plane I have ordered (Electrifly Super Sportster rxr) as a specific example---It has a motor of unknown details, an ESC of 18 amps, and a recommended 3-cell battery of 1300A and 30C discharge rate. QUESTION----Assuming weight is NOT a factor, can I safely use a 1300A 20C??? A 1500A 20C??? How about a 1800A 20C??? What would be the UNQUESTIONABLE result of reducing the C from 30 to 20? Are these figures cast in stone or are they wild estimates?
Is there a simple method of converting one of these to the other?
Your input would be greatly appreciated. Thanks. Gary
garyp1029 is offline  
  Reply With Quote
Old 04-19-2014, 04:52 AM   #2
fhhuber
Super Contributor
 
fhhuber's Avatar
 
Join Date: Mar 2013
Posts: 2,097
Thanked 209 Times in 200 Posts
iTrader: (0)
Friends: (1)
Default

"C" rating has to do with internal resistance of the battery and other factors and is a somewhat non-standard "quantity"

It (supposedly) means you can "continuously" disharge at X * capacity

But "continuous" can mean for up to 1 minute or for the whole pack's charge or just about anything the person who slapped the label on wants it to mean...

There's an infamous battery maker's claim of 150C (drain the pack flat in 24 seconds) where the pack had wires which would melt at that current in under 5 seconds.

C rating meanings are pretty consistent within any given brand and as long as you are comparing within one brand they are useful.
Don't try to equate the 20C of Sky LiPo vs Turnigy vs Thunder Power vs Polyquest vs Max Amps packs. If they have any relationship its accidental.

20C will have higher internal resistance than 30C and will get hotter under the same load. You'll also waste a little more of the pack energy creating that heat.

Within the same brand packs you can expect higher C to give SLIGHTLY better peak performance at the cost of a bit of duration (due to higher current flow). Unless you are demanding high current you may not be able to notice it.

You can't even really compare the capacity of different brands well... what one labels 2000 ma another might label 1800 or 2200. I have a 3S 2200 ma 20C "Dynam" labeled pack that gives less duration than a 3S 1800 ma 20C Sky LiPo
fhhuber is offline  
  Reply With Quote
Old 04-19-2014, 05:42 AM   #3
kyleservicetech
Dennis V
 
kyleservicetech's Avatar
 
Join Date: Apr 2008
Location: Wisconsin, USA
Posts: 7,934
Thanked 683 Times in 666 Posts
Club: www.racinercclub.com (I'm the newsletter editor)
Awards Showcase

Outstanding Contributor Award  3kW  2kW  100mph Speed Demon 
iTrader: (1)
Friends: (20)
Default

Originally Posted by fhhuber View Post

There's an infamous battery maker's claim of 150C (drain the pack flat in 24 seconds) where the pack had wires which would melt at that current in under 5 seconds.
Yeah, here you go on that batteries 150C claim.

http://www.wattflyer.com/forums/show...highlight=150c

IMHO, that 150C rating isn't worth the paper its written on. I'm sure it is a good battery. But 150C

This company is still claiming 150C on their batteries:
http://www.maxamps.com/Lipo-8000-185-DC-Pack.htm

DennyV
Retired and the days are just too short, busier than ever!
kyleservicetech is offline  
  Reply With Quote
Old 04-19-2014, 05:59 AM   #4
solentlife
Super Contributor
 
solentlife's Avatar
 
Join Date: Oct 2010
Location: Ex UK Brit now in Latvia west coast - Ventspils
Posts: 5,922
View solentlife's Gallery47
Thanked 235 Times in 232 Posts
Club: Founder Member Ventspils RC Club. Ex Waltham Chase and Meon Valley Soaring.
Awards Showcase

Scratchbuilders Award  Scratchbuilders Award  Outstanding Contributor Award  125mph Speed Demon 
iTrader: (0)
Friends: (15)
Default

To the OP .... Denny's knowledge is far exceeding most ... so go with him !

Taking your post ... you ask if it's OK to use a lower C rated in a model. Yeh go ahead - BUT don't expect to have same performance ... Don't expect battery to last the punishment you will subject it to.

If a model is spec'd for 30C - then using a 20C is definitely NOT recommended. The only time you could get away with that is if you increased the size of the pack to get back to AMP capability ...

Example :

1500mAh pack of 30C = amp capability of 1.5 x 30 = 45A

you would need a pack of 45 / 20 = 2250mAh size at least to get same amp capability in 20C rating

But as in most things in life - theory does not always work out ... trying to run a pack at full output amp capability means you better have a big wallet and plenty of money in it !

There is another factor - most model spec's under state the real requirements for battery packs ... and I usually find an increase in C rated pack is needed. In this case where your model calls for a 30C ... I would be looking at a 35C or more ... just to get that full output it probably needs.

Nigel

222kph PKJ,EDF Concorde, Mini4,Mig3,T45,PKJ twin,ME109,Edge540,Cessna182,Skymaster Biplane,F15,F16,Badius,Ultimate,SE5,Qbee10,450 Heli,V911,J3 Cub Founder 9x forum: http://groups.yahoo.com/group/Flysky_RC_radio/
- Subscribe my Youtube: "solentlifeuk"
solentlife is online now  
  Reply With Quote
Old 04-19-2014, 06:06 AM   #5
kyleservicetech
Dennis V
 
kyleservicetech's Avatar
 
Join Date: Apr 2008
Location: Wisconsin, USA
Posts: 7,934
Thanked 683 Times in 666 Posts
Club: www.racinercclub.com (I'm the newsletter editor)
Awards Showcase

Outstanding Contributor Award  3kW  2kW  100mph Speed Demon 
iTrader: (1)
Friends: (20)
Default

Originally Posted by solentlife View Post

Taking your post ... you ask if it's OK to use a lower C rated in a model. Yeh go ahead - BUT don't expect to have same performance ... Don't expect battery to last the punishment you will subject it to.
Out of curiosity, has anyone ever taken a hand full of batteries from a given supplier with the same mah rating, and different "C" ratings, and determined how much better the higher "C" rated batteries hold their voltage under load?

That would be very good information.

DennyV
Retired and the days are just too short, busier than ever!
kyleservicetech is offline  
  Reply With Quote
Old 04-19-2014, 06:14 AM   #6
fhhuber
Super Contributor
 
fhhuber's Avatar
 
Join Date: Mar 2013
Posts: 2,097
Thanked 209 Times in 200 Posts
iTrader: (0)
Friends: (1)
Default

Originally Posted by kyleservicetech View Post
Out of curiosity, has anyone ever taken a hand full of batteries from a given supplier with the same mah rating, and different "C" ratings, and determined how much better the higher "C" rated batteries hold their voltage under load?

That would be very good information.
There have been people who were doing those tests... but it gets expensive to get all the batteries to test.

General results (with the same capacity and cell count) within any one brand showed higher C rated could deliver more current (lower internal resistance) but for a shorter time (because its the same total watt-hr capacity) The higher C rated packs didn't get as hot under the same load, as expected with the lower internal resistance.


Comparing one brand to another... the numbers on the packs were essentially not reliable.
fhhuber is offline  
  Reply With Quote
Old 04-19-2014, 06:18 AM   #7
solentlife
Super Contributor
 
solentlife's Avatar
 
Join Date: Oct 2010
Location: Ex UK Brit now in Latvia west coast - Ventspils
Posts: 5,922
View solentlife's Gallery47
Thanked 235 Times in 232 Posts
Club: Founder Member Ventspils RC Club. Ex Waltham Chase and Meon Valley Soaring.
Awards Showcase

Scratchbuilders Award  Scratchbuilders Award  Outstanding Contributor Award  125mph Speed Demon 
iTrader: (0)
Friends: (15)
Default

Originally Posted by kyleservicetech View Post
Out of curiosity, has anyone ever taken a hand full of batteries from a given supplier with the same mah rating, and different "C" ratings, and determined how much better the higher "C" rated batteries hold their voltage under load?

That would be very good information.
Being a 'scrooge' .. I tend to not take my own advice !! I do try at times ti skimp on batterys ... trying to buy lowest C rated and size I can ... but it really does prove false economy.

I have found that Nanotechs may give their rated but not for long ... they soon grind down and become worse than their lowest rating (nanos of HK have dual C rates ie 25-50 ... etc.)

Rhinos - I find tend to be good and produce near enough what they label. They also seem to last reasonably well.

Turnigy blue - Generally I find are reasonable but C ratings can be a little optimistic, life ? generally if not called too often to full rate - similar to Rhino.

Zippy - same as Turnigy Blue

Zippy Compacts - same as Turnigy Blue except for one aspect - continued punishment will crap them out earlier than Blue. They puff up easily.

My best packs in fact are ones that I can no longer find ... E-Tech, I have a couple that getting on 3 years old and they have been abused something terrible ... and they still produce nigh on C rate and performance. They look battered and beaten up ... I reckon half the people on here would bin them - they do look beaten ! But boy do they put out ! Where did I get them ? Ebay !! I bought them because they had a different more square shape and fitted my T45 50mm better ... They now drag my Cessna and other models around since I upped my 50mm's to 4S.

I am a Rhino user except where I can't get the C and size I want .. then it's Compact or Blue.

Nigel

222kph PKJ,EDF Concorde, Mini4,Mig3,T45,PKJ twin,ME109,Edge540,Cessna182,Skymaster Biplane,F15,F16,Badius,Ultimate,SE5,Qbee10,450 Heli,V911,J3 Cub Founder 9x forum: http://groups.yahoo.com/group/Flysky_RC_radio/
- Subscribe my Youtube: "solentlifeuk"
solentlife is online now  
  Reply With Quote
Old 04-19-2014, 05:04 AM   #8
pizzano
Behold The Renaissance
 
pizzano's Avatar
 
Join Date: May 2012
Location: So. Calif
Posts: 1,106
Thanked 69 Times in 67 Posts
Club: AMA, Marks, Pomona Valley, Prado Dam
iTrader: (0)
Friends: (3)
Default

Well.....if you read everything, then this link should have helped:

http://www.wattflyer.com/forums/showthread.php?t=65869

It's a little techie....but the best explanation I've seen yet....Denny knows his stuff!

You stated that "weight is not a factor".....but keep in mind weight is an issue related to both mAh, "C" value and C/G........very few RC air craft are not affected by C/G or the weight distribution factor going up or down dramatically in mAh & "C" value.

Also, many here and at other forums have found the "C" value stated on most low to mid quality batteries can be very mis-leading, especially when the "C" is over the 30 value.

Also...."C" factor is often referred to as the "burst" rate related in amps the battery can safely deliver within a given time cycle (say 10 sec.).....it's quite common to need higher "burst" rates in muti-prop craft or extremely acrobatic planes.......for the obvious reasons!

AMA 928214
pizzano is offline  
  Reply With Quote
Old 04-19-2014, 05:17 AM   #9
kyleservicetech
Dennis V
 
kyleservicetech's Avatar
 
Join Date: Apr 2008
Location: Wisconsin, USA
Posts: 7,934
Thanked 683 Times in 666 Posts
Club: www.racinercclub.com (I'm the newsletter editor)
Awards Showcase

Outstanding Contributor Award  3kW  2kW  100mph Speed Demon 
iTrader: (1)
Friends: (20)
Default

Originally Posted by garyp1029 View Post
I have read "Everything you Want To Know . . ." as well as several other posts concerning C discharge and I still don't get it. I understand that C is a discharge rate of drawing a certain quantity in a specified time period, BUT EXACTLY HOW does it affect real life choices? Using a plane I have ordered (Electrifly Super Sportster rxr) as a specific example---It has a motor of unknown details, an ESC of 18 amps, and a recommended 3-cell battery of 1300A and 30C discharge rate. QUESTION----Assuming weight is NOT a factor, can I safely use a 1300A 20C??? A 1500A 20C??? How about a 1800A 20C??? What would be the UNQUESTIONABLE result of reducing the C from 30 to 20? Are these figures cast in stone or are they wild estimates?
Is there a simple method of converting one of these to the other?
Your input would be greatly appreciated. Thanks. Gary
That "C" term is a general term that describes just how fast your battery can be discharged. The same thing applies to how fast you can recharge your battery.

If the battery mfg is honest in their specs, the higher the "C" rating, the better the battery will put out high currents without the battery voltage sagging to much. Kind of like an old lead acid car battery that can barely turn over your engine, as compared to a brand new battery.

IMHO, any C rating above perhaps 60 or so leads to diminishing returns. If you actually discharged a battery at 60C for the entire flight, your flight time would be less than one minute.

If you discharge your battery at a rate of 30C, that indicates a flight time of two minutes assuming full power for the entire flight. And, 20C would be three minutes.

Now, you've got the batteries MAXIMUM current capability, defined as per example, 30C. With a 1300 Mah battery, that is 1.3 Amp Hours. So, 30C would be 30C times 1.3 Amp Hours, or a maximum current of 39 Amps.

And, you've got "Flight" "C" which is how hard you are actually operating your battery. If you're pulling 22 Amps on a 1.3 Amp Hour battery, the value of C would be 22/1.3 or C= 16.92. Flight time would be 60 minutes/16.92 or about 3 1/2 minutes at full throttle for the entire flight.

Problem is, most battery mfg's don't indicate how long your battery will last running it at maximum C. We've had some guys in my club that only got 5 flights before the battery was junk.

Flight time is equal to 60 minutes divided by the "C" value actually being used while in flight.

And as Pizzano indicated, I've got a thread on this subject:

"C" and what it is
http://www.wattflyer.com/forums/showthread.php?t=65869

Hope that helps

DennyV
Retired and the days are just too short, busier than ever!
kyleservicetech is offline  
  Reply With Quote
Old 04-19-2014, 05:20 AM   #10
pizzano
Behold The Renaissance
 
pizzano's Avatar
 
Join Date: May 2012
Location: So. Calif
Posts: 1,106
Thanked 69 Times in 67 Posts
Club: AMA, Marks, Pomona Valley, Prado Dam
iTrader: (0)
Friends: (3)
Default

Beat ya to it Denny.......LOL.......that link (thread) you put together is the best one I've ever seen on any forum......that's why I refer to it still today......

AMA 928214
pizzano is offline  
  Reply With Quote
Old 04-19-2014, 05:33 AM   #11
kyleservicetech
Dennis V
 
kyleservicetech's Avatar
 
Join Date: Apr 2008
Location: Wisconsin, USA
Posts: 7,934
Thanked 683 Times in 666 Posts
Club: www.racinercclub.com (I'm the newsletter editor)
Awards Showcase

Outstanding Contributor Award  3kW  2kW  100mph Speed Demon 
iTrader: (1)
Friends: (20)
Default

Originally Posted by pizzano View Post
Beat ya to it Denny.......LOL.......that link (thread) you put together is the best one I've ever seen on any forum......that's why I refer to it still today......

Thanks!

This old geezer has had some 50 years experience in this electric stuff, so some of it does sink in after awhile.

DennyV
Retired and the days are just too short, busier than ever!
kyleservicetech is offline  
  Reply With Quote
Old 04-19-2014, 05:51 AM   #12
xmech2k
Ya got any Beeman's?
 
xmech2k's Avatar
 
Join Date: Apr 2009
Location: San Diego, CA
Posts: 2,545
View xmech2k's Gallery21
Thanked 239 Times in 237 Posts
Club: CVMRCC, SEFSD
Awards Showcase

1kW  Outstanding Contributor Award 
iTrader: (0)
Friends: (7)
Default

Gary, the most important thing is that your battery can supply the power demanded by your esc and motor. That's measured in amps. To determine how many amps your battery is rated to safely run at, you just use the equation you probably already learned:

(mAh/1000)xC

So in your examples above, your 1300 mah 20 C battery can safely provide 26 amps. The 1500 mah 20 C can provide 30 amps.

Your motor/prop determines how many amps the system needs. The esc must be rated to handle it. The battery must also be rated to supply it. If you get too close to a batteries limits, or is old and/or abused, it can suffer from voltage sag when under load, causing poor performance.

I hope this is along the lines of the info you're looking for.
xmech2k is offline  
  Reply With Quote
Old 04-19-2014, 05:58 AM   #13
kyleservicetech
Dennis V
 
kyleservicetech's Avatar
 
Join Date: Apr 2008
Location: Wisconsin, USA
Posts: 7,934
Thanked 683 Times in 666 Posts
Club: www.racinercclub.com (I'm the newsletter editor)
Awards Showcase

Outstanding Contributor Award  3kW  2kW  100mph Speed Demon 
iTrader: (1)
Friends: (20)
Default

Originally Posted by xmech2k View Post

(mAh/100)xC

So in your examples above, your 1300 mah 20 C battery can safely provide 26 amps. The 1500 mah 20 C can provide 30 amps.

Your motor/prop determines how many amps the system needs. The esc must be rated to handle it. The battery must also be rated to supply it. If you get too close to a batteries limits, or is old and/or abused, it can suffer from voltage sag when under load, causing poor performance.

I hope this is along the lines of the info you're looking for.
Oops, you left a zero off

Maximum current equals (mah/1000)xC

Good point on the motor and prop specs. Just changing the prop by several sizes can have a drastic effect on the "Effective C" being used during flight. From not being able to get off the ground with to small of a prop, to having wild power with to big of a prop, with smoke soon to follow.

DennyV
Retired and the days are just too short, busier than ever!
kyleservicetech is offline  
  Reply With Quote
Old 04-19-2014, 06:11 AM   #14
fhhuber
Super Contributor
 
fhhuber's Avatar
 
Join Date: Mar 2013
Posts: 2,097
Thanked 209 Times in 200 Posts
iTrader: (0)
Friends: (1)
Default

Well... you can fly using the recommended every time.

You will often be better off with higher C rating especially dealing with high demand applications (Like EDFs)

Yo can also do just fine with lower C than recommended in many cases. I'm only using 20C rated packs for my big EDF... 12S 5000 mah, pulling briefly 105 amps (last reading before the Wattmeter smoked), averaging about 60 amps (calculated from time vs what it takes to recharge) over the 4 minutes I fly it per charge.
fhhuber is offline  
  Reply With Quote
Old 04-19-2014, 04:03 PM   #15
fhhuber
Super Contributor
 
fhhuber's Avatar
 
Join Date: Mar 2013
Posts: 2,097
Thanked 209 Times in 200 Posts
iTrader: (0)
Friends: (1)
Default

Difference in weight/size of a 1300 ma vs 1500 ma is small. That should be very easy. The 1800 might take a little thought but still shouldn't be too hard s there is usually some space all around the battery pack.

We don't just stuff in the biggest battery that fits... we consider first the minimum needs to fly the model (voltage and current delivery) and the desired minimum duration. Then we consider the weight and its effects on the model.

If added weight won't affect performance excessively THEN the larger capacity battery is appropriate.

Doubling battery capacity will not double flight time. More weight requires more minimum airspeed to maintain flight and that means more power is required, draining the battery faster. (You can even reduce flight time by adding too much battery.)

More weight generally means a lower top speed and reduced aerobatic performance.

More weight can mean more damage in a minor crash.
fhhuber is offline  
  Reply With Quote
Old 04-19-2014, 05:09 PM   #16
kyleservicetech
Dennis V
 
kyleservicetech's Avatar
 
Join Date: Apr 2008
Location: Wisconsin, USA
Posts: 7,934
Thanked 683 Times in 666 Posts
Club: www.racinercclub.com (I'm the newsletter editor)
Awards Showcase

Outstanding Contributor Award  3kW  2kW  100mph Speed Demon 
iTrader: (1)
Friends: (20)
Default

Originally Posted by fhhuber View Post
Difference in weight/size of a 1300 ma vs 1500 ma is small. That should be very easy. The 1800 might take a little thought but still shouldn't be too hard s there is usually some space all around the battery pack.

We don't just stuff in the biggest battery that fits... we consider first the minimum needs to fly the model (voltage and current delivery) and the desired minimum duration. Then we consider the weight and its effects on the model.

If added weight won't affect performance excessively THEN the larger capacity battery is appropriate.

Doubling battery capacity will not double flight time. More weight requires more minimum airspeed to maintain flight and that means more power is required, draining the battery faster. (You can even reduce flight time by adding too much battery.)

More weight generally means a lower top speed and reduced aerobatic performance.

More weight can mean more damage in a minor crash.
Very good points.

One of those computer programs such as www.motocalc.com will help in the selection of your battery. Problem with motocalc though, it's only as accurate as the specifications on the motor you are using.

Some of those specs are way the heck off, resulting in those computer programs giving inaccurate results.

DennyV
Retired and the days are just too short, busier than ever!
kyleservicetech is offline  
  Reply With Quote
Old 04-19-2014, 05:21 PM   #17
JetPlaneFlyer
Super Contributor
 
JetPlaneFlyer's Avatar
 
Join Date: Mar 2009
Location: Aberdeen, Scotland
Posts: 4,327
Thanked 477 Times in 445 Posts
Awards Showcase

5kW  Outstanding Contributor Award  1kW 
iTrader: (0)
Friends: (8)
Default

As a rule of thumb for trainers and sports models 20c-25c should be fine, for fast aerobatics and 3D models then 25-30c is enough. Higher c ratings are usually only an advantage the likes of racers, EDFs and helis that have very high current demand and short flight times.

But higher c rating doesn't do any harm other that costing more and usually being a few grams heavier.
JetPlaneFlyer is online now  
  Reply With Quote
Old 04-20-2014, 02:50 PM   #18
Wrongway-Feldman
Member
 
Join Date: Jan 2011
Location: Govan, Saskatchewan
Posts: 599
Thanked 32 Times in 32 Posts
iTrader: (0)
Friends: (5)
Default

I have found in recent years that plane manufacturers are listing higher and higher C requirements for their models. And I can't for the life of me figure it out.
There are models on the market today that have not changed in years that originally required a 15C battery that now require a 30C pack. Specs on the plane have not changed. ESC rating has not changed.
I wish I could remember the name of the manufacturer but I had a large J3 cub that a few years ago required a 4S 3300 at 20C. Plane had a 30amp ESC and a 36xx motor.
A friend bought that exact same model still sold in the same packaging last fall. Still has the same motor and ESC but now requires a 4S 3300 30c. I'm starting to think that for many manufacturers it is all just a bit of hype.
Parkzone still uses all 15c packs, I think we can agree that parkzone is no slouch in this industry.
I have used batteries from all makes, except the expensive ones cause I'm cheap, and have virtually no difference in performance between any of them. I treat mine poorly, I forget to set them to a storage charge, I charge them and then forget I charged them and leave em laying around months.
I've never had one puff. Had a chicklet 1S go poof on the charger once but that's it.
I don't even know how many cycles on my packs cause I don't log it.

The only thing I look at is what the amp draw from a motor ESC combo will be.
I then look at weight capacity of said model and room for the pack. I then go with the biggest pack that will realistically fly. It is rare that I've ever required more than 20C out of a pack. Other than a 1300 watt 70mm edf I have. But that's another story.

----------------------------------------------------------
Dumas Ecroupe, MM EVA, E-flite L4 Grasshopper, Sig Kougar, Sig Kobra, Top Fight Contender, top flite mini contender, Carl Goldberg Skylark mark II, M&H Sportster 40.
Wrongway-Feldman is offline  
  Reply With Quote
Old 04-20-2014, 02:58 PM   #19
solentlife
Super Contributor
 
solentlife's Avatar
 
Join Date: Oct 2010
Location: Ex UK Brit now in Latvia west coast - Ventspils
Posts: 5,922
View solentlife's Gallery47
Thanked 235 Times in 232 Posts
Club: Founder Member Ventspils RC Club. Ex Waltham Chase and Meon Valley Soaring.
Awards Showcase

Scratchbuilders Award  Scratchbuilders Award  Outstanding Contributor Award  125mph Speed Demon 
iTrader: (0)
Friends: (15)
Default

Most factory specs I read are too low in C rating as well as small packs.

Good example are the 50mm EDF jets that spec at 800mAh 3S 20C. They fly but lack any get up and go. Give them a higher C or larger pack and then they come alive.

My Badius Pattern plane is spec'd for a 1300 3S 20C ... believe me - put a 1750 3S 25C in and see it fly much better.... improved thrust, improved balance etc.

I rarely bother with factory spec packs in models now ... having found that a modest increase pays of dividends.

Nigel

222kph PKJ,EDF Concorde, Mini4,Mig3,T45,PKJ twin,ME109,Edge540,Cessna182,Skymaster Biplane,F15,F16,Badius,Ultimate,SE5,Qbee10,450 Heli,V911,J3 Cub Founder 9x forum: http://groups.yahoo.com/group/Flysky_RC_radio/
- Subscribe my Youtube: "solentlifeuk"
solentlife is online now  
  Reply With Quote
Old 04-21-2014, 12:41 AM   #20
kyleservicetech
Dennis V
 
kyleservicetech's Avatar
 
Join Date: Apr 2008
Location: Wisconsin, USA
Posts: 7,934
Thanked 683 Times in 666 Posts
Club: www.racinercclub.com (I'm the newsletter editor)
Awards Showcase

Outstanding Contributor Award  3kW  2kW  100mph Speed Demon 
iTrader: (1)
Friends: (20)
Default

Originally Posted by Wrongway-Feldman View Post
I have found in recent years that plane manufacturers are listing higher and higher C requirements for their models. And I can't for the life of me figure it out.
There are models on the market today that have not changed in years that originally required a 15C battery that now require a 30C pack. Specs on the plane have not changed. ESC rating has not changed.
I wish I could remember the name of the manufacturer but I had a large J3 cub that a few years ago required a 4S 3300 at 20C. Plane had a 30amp ESC and a 36xx motor.
A friend bought that exact same model still sold in the same packaging last fall. Still has the same motor and ESC but now requires a 4S 3300 30c. I'm starting to think that for many manufacturers it is all just a bit of hype.
Parkzone still uses all 15c packs, I think we can agree that parkzone is no slouch in this industry.
I have used batteries from all makes, except the expensive ones cause I'm cheap, and have virtually no difference in performance between any of them. I treat mine poorly, I forget to set them to a storage charge, I charge them and then forget I charged them and leave em laying around months.
I've never had one puff. Had a chicklet 1S go poof on the charger once but that's it.
I don't even know how many cycles on my packs cause I don't log it.

The only thing I look at is what the amp draw from a motor ESC combo will be.
I then look at weight capacity of said model and room for the pack. I then go with the biggest pack that will realistically fly. It is rare that I've ever required more than 20C out of a pack. Other than a 1300 watt 70mm edf I have. But that's another story.
Methinks these model mfgs are specifying higher "C" battery ratings because of who is providing the capabilities of those batteries. That "C" rating might be provided by the battery mfg marketing department, rather than the Engineers.

What used to be a "20C" rating, is now updated to perhaps "40C", with the same exact battery. What happens is, if you actually use it at 40C, you might get 10 or 20 flights out of the battery before it looses its stuff.

That happened to a couple of club members. One got five flights each out of three different batteries from the same mfg, before the batteries turned into expensive paperweights. He was running them at the max "C" rating.

DennyV
Retired and the days are just too short, busier than ever!
kyleservicetech is offline  
  Reply With Quote
Old 04-21-2014, 04:44 AM   #21
solentlife
Super Contributor
 
solentlife's Avatar
 
Join Date: Oct 2010
Location: Ex UK Brit now in Latvia west coast - Ventspils
Posts: 5,922
View solentlife's Gallery47
Thanked 235 Times in 232 Posts
Club: Founder Member Ventspils RC Club. Ex Waltham Chase and Meon Valley Soaring.
Awards Showcase

Scratchbuilders Award  Scratchbuilders Award  Outstanding Contributor Award  125mph Speed Demon 
iTrader: (0)
Friends: (15)
Default

I always take max burst rate of a cell as a joke ! Even the max sustained will often prove the death of a pack.

Problem is many models cannot take a suitably higher rated pack in size or weight before it compromises performance.

Most models are in my view quoted low in battery size / C rate ... it's marketing. Bit like cars where they love to quote how economic a compact is. But the overall performance is no better than a shopping trolley.

Nigel

222kph PKJ,EDF Concorde, Mini4,Mig3,T45,PKJ twin,ME109,Edge540,Cessna182,Skymaster Biplane,F15,F16,Badius,Ultimate,SE5,Qbee10,450 Heli,V911,J3 Cub Founder 9x forum: http://groups.yahoo.com/group/Flysky_RC_radio/
- Subscribe my Youtube: "solentlifeuk"
solentlife is online now  
  Reply With Quote
Old 04-21-2014, 04:51 AM   #22
kyleservicetech
Dennis V
 
kyleservicetech's Avatar
 
Join Date: Apr 2008
Location: Wisconsin, USA
Posts: 7,934
Thanked 683 Times in 666 Posts
Club: www.racinercclub.com (I'm the newsletter editor)
Awards Showcase

Outstanding Contributor Award  3kW  2kW  100mph Speed Demon 
iTrader: (1)
Friends: (20)
Default

Originally Posted by solentlife View Post
I always take max burst rate of a cell as a joke ! Even the max sustained will often prove the death of a pack.

Problem is many models cannot take a suitably higher rated pack in size or weight before it compromises performance.

Most models are in my view quoted low in battery size / C rate ... it's marketing. Bit like cars where they love to quote how economic a compact is. But the overall performance is no better than a shopping trolley.

Nigel
As far as killing a battery, one of my club members just flew his foamie jet with a 4 cell 2200 Mah battery in place of a 3 cell pack. He flew it to LVC. Each cell measured about 2.2 Volts DC.

Now his brand new battery that cost some $60, provided just one flight.

IMHO, that LVC is like the oil pressure idiot light on your car. When it lights up, you've potentially got engine damage.

DennyV
Retired and the days are just too short, busier than ever!
kyleservicetech is offline  
  Reply With Quote
Old 04-20-2014, 03:13 PM   #23
dahawk
Super Contributor
 
dahawk's Avatar
 
Join Date: Jul 2011
Location: Keller, TX
Posts: 3,347
View dahawk's Gallery6
Thanked 203 Times in 199 Posts
Club: 114th RC Aero Squadron
iTrader: (0)
Friends: (19)
Default

Simple for me. More C is better ! On my mostly small plane squadron, I don't buy anything with less than a 30C rating anymore whether it's 3S,4S or 5S.

Seriously though, a lot of pilots jump on souping up their craft by simply going to more voltage and higher c rated lipos. "Hey, I wanna throw a 4 cell in that thing !"

Sometimes left behind is 1). the motor's ability to handle the higher voltage and 2). the amps being pulled through the speed controller that doesn't have enough capacity to handle. Can make for a bad recipe .

Wounded Warrior Fun Fly - Aug 16th ,2014 - Grapevine TX - Info link: https://support.woundedwarriorprojec...ising/RCPilots
dahawk is offline  
  Reply With Quote
Old 04-20-2014, 03:58 PM   #24
fhhuber
Super Contributor
 
fhhuber's Avatar
 
Join Date: Mar 2013
Posts: 2,097
Thanked 209 Times in 200 Posts
iTrader: (0)
Friends: (1)
Default

20C has been doing just fine for me for EDFs....

The increase in power by increasing C and using the same capacity cells is marginal really. I tried higher C cells and all it really did for me was cost more.

You can't say its cheap motors and ESCS... BVM EVF which has a Neu motor custom made for BVM and the Castle ESC that was THE top of the line highest current rated ESC when the fan was produced.
fhhuber is offline  
  Reply With Quote
Old 04-20-2014, 04:06 PM   #25
xmech2k
Ya got any Beeman's?
 
xmech2k's Avatar
 
Join Date: Apr 2009
Location: San Diego, CA
Posts: 2,545
View xmech2k's Gallery21
Thanked 239 Times in 237 Posts
Club: CVMRCC, SEFSD
Awards Showcase

1kW  Outstanding Contributor Award 
iTrader: (0)
Friends: (7)
Default

I think in one case, Blade helicopters I think, their C recommendation went up because they quit carrying the lower C rated batteries. They were just matching the batteries they currently carry.
xmech2k is offline  
  Reply With Quote
Reply

  WattFlyer RC Electric Flight Forums - Discuss radio control eflight > Electric R/C Airplanes > General Electric Discussions

« Previous Thread | Next Thread »

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Discharge down a LiPo pack solentlife Batteries & Chargers 164 11-14-2013 07:29 AM
Sneak Peek at the NEW Cellpro PowerLab 8 Tim Marks FMA Direct 63 09-21-2012 05:09 AM
New Lipo propblem to me, looking for safe terminal discharge dumo01 Batteries & Chargers 5 03-26-2012 12:43 PM
How far to discharge LiPo's JetPlaneFlyer Power Systems 14 07-29-2011 06:11 PM
FMA Cellpro PowerLab 8 regenerative discharge power source? miernik FMA Direct 3 04-15-2011 07:15 PM


All times are GMT +1. The time now is 07:47 PM.


Powered by: vBulletin
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright 2005 WattfFlyer.com
RCU Eflight HQ

Charities we support Select: Yorkie Rescue  ::  Crohn's & Colitis Foundation



Page generated in 0.71733 seconds with 67 queries