Dec 06, 2012, 04:33 PM
Grumpy old git.. Who me?
Aberdeen
Joined Mar 2006
13,010 Posts
Quote:
 Originally Posted by nickelbn1 I just used that calculator. So if my highest IR is 18 and its a 3300mah pack, i am only getting a 10c discharge? So my 40c pack is really like 10c.....??
If the cells are getting up around the 18 milliohm mark then probably time to retire the pack before you hit LVc just at the wrong moment. Maybe try it with a Wattmeter on the plane and see how the voltage holds up under load.

Having said that, if you are getting acceptable performance in flight then there isnt really a problem. I know for sure though that on my batteries I can tell by the way they perform a long time before they get that bad.
 Dec 06, 2012, 04:43 PM fly and then fly some more! Springdale, AR Joined Dec 2006 2,178 Posts This 5s sky with the high readings around 18 milliohms is still performing well as ever. I definitely would not say its time for retirement.
Dec 06, 2012, 04:45 PM
Grumpy old git.. Who me?
Aberdeen
Joined Mar 2006
13,010 Posts
Quote:
 Originally Posted by Vince_TT Are you guys talking in Mars? Seriously, I would like to learn more about the IR as well.
It's simple enough.
I.R. = internal resistance
Its measured in milliohms (1000 milliohm = 1 ohm)

Simplistically it's just the resistance of the battery to the flow of electricity. The higher the resistance the more voltage drop you get when current flows through the battery so the more voltage 'sag' you get at the battery output terminals also the more heat is generated inside the battery.
Larger capacity batteries give a 'wider' pathway for electricity to flow through so less resistance, in the same way that thick wires have less resistance than thin ones.
There should in theory also be a link between 'c' rating and I.R. . Higher 'c' rating should have lower resistance so lower I.R. number. Trouble is some manufacturers are a bit 'creative' when it comes to 'c' rating. Measuring I.R gives you a good idea of what the 'c' rate really is.
Dec 06, 2012, 04:50 PM
Grumpy old git.. Who me?
Aberdeen
Joined Mar 2006
13,010 Posts
Quote:
 Originally Posted by nickelbn1 This 5s sky with the high readings around 18 milliohms is still performing well as ever. I definitely would not say its time for retirement.
That's odd because you should easily notice if the battery was that bad (unless you aren't using the batteries very hard at all). Checking what voltage the battery holds at WOT when it's fully charged is the acid test. A good battery will hold around 3.8v per cell or more when run near it's c rate limit.
 Dec 06, 2012, 04:50 PM fly and then fly some more! Springdale, AR Joined Dec 2006 2,178 Posts So as i asked earlier, if my pack is 3300mah and my highest ir is 18, i am only getting a 10c discharge?
Dec 06, 2012, 04:52 PM
Grumpy old git.. Who me?
Aberdeen
Joined Mar 2006
13,010 Posts
Quote:
 Originally Posted by nickelbn1 So as i asked earlier, if my pack is 3300mah and my highest ir is 18, i am only getting a 10c discharge?
Yes, if the measured I.R. is accurate then the 'true' c rating is more like 10c meaning your safe constant discharge rate is around 33Amps.

Which is why i mentioned retirement. Personally I think that online tool is a little pessimistic but it's still a good guide.
 Dec 06, 2012, 06:23 PM fly and then fly some more! Springdale, AR Joined Dec 2006 2,178 Posts ok, when I first tested my gens 3300mah 5s, it was at storage voltage. I just finished charging it and tested it again and now it shows way lower. first test was 9,3,7,4,5 fully charged was now 8,2,4,2,2 ????
 Dec 09, 2012, 02:32 PM Fly it 'till it breaks. United States, CA, Los Angeles Joined May 2011 721 Posts Did a little hucking with a fellow Edge flyer yesterday. We probably should have tried to choreograph something, but it was still a lot of fun just winging it Best viewed in HD
Dec 09, 2012, 03:06 PM
Grumpy old git.. Who me?
Aberdeen
Joined Mar 2006
13,010 Posts
Quote:
 Originally Posted by nickelbn1 ok, when I first tested my gens 3300mah 5s, it was at storage voltage. I just finished charging it and tested it again and now it shows way lower. first test was 9,3,7,4,5 fully charged was now 8,2,4,2,2 ????
I.R. seems to go much higher if the battery is in a discharged state.
 Dec 09, 2012, 08:29 PM FLYAK United States, AK, Anchorage Joined Oct 2011 5,667 Posts So I was gong to sell this plane since it was barely getting any use now that I have the 60" Edge. Put the skis on her today and there is no way in h*ll I am letting it go. Awesome plane on skis.
 Dec 11, 2012, 02:36 PM fly and then fly some more! Springdale, AR Joined Dec 2006 2,178 Posts Tried my first knife edge on this plane last weekend. Wow. Sooo much easier then with my past planes. It just locks right in. So nice.
 Dec 11, 2012, 02:50 PM Grumpy old git.. Who me? Aberdeen Joined Mar 2006 13,010 Posts It does KE great, only a tiny hint of coupling. Massive rudder authority and no sign of any snap out of Ke at high alpha, like some other 3D planes do. Try some KE loops, they are easy with the Edge. setting up some mixes on the Tx to get rid of what little coupling there is makes life even easier.
 Dec 11, 2012, 06:35 PM fly and then fly some more! Springdale, AR Joined Dec 2006 2,178 Posts excuse me for sounding like a newbie, but I am trying to learn all the names for things....what is coupling?
 Dec 11, 2012, 07:32 PM They Call him Dead! United States, SC, Pawleys Island Joined Jul 2003 7,576 Posts Well I just wrote about 6 paragraphs to explain coupling and then pushed the back button and it is gone. I can't bring myself to do it again right now. Go here for the short answer and PM me if you need more: http://www.rcuniverse.com/forum/m_9495166/tm.htm It is possible to program a mix to get rid of coupling but there are other things you should do before you mix
 Dec 12, 2012, 12:49 AM Grumpy old git.. Who me? Aberdeen Joined Mar 2006 13,010 Posts here's a copy and paste of a response to the same question that I wrote elswhere... Coupling is an interaction between controls across the different axis of freedom. In principal each of the primary controls on a plane effect one axis of freedom:Elevator controls pitch Rudder controls yaw Ailerons control roll In practice it's not quite that simple. What you often find is that operation of one control has not only the desired effect (i.e. rudder causes yaw) but it has a secondary effect on one or both of the other axis. Taking rudder again as an example; when you apply rudder you often find that you get not only the desired yaw effect but the plane will also roll and pitch slightly. Rudder is usually the ‘worst offender’ for cross coupling but aileron suffers from it too. It’s not unusual that when you apply aileron the plane not only rolls as you intended but it yaws in the direction opposite to roll direction (plane rolls right and yaws left). This is known as ‘adverse yaw’. For some planes coupling is essential for proper control. Rudder and elevator control planes being the obvious example where we rely on the rudder to roll coupling in order to make the plane bank into a turn. Without coupling a rudder and elevator plane would be un-flyable. For aerobatic planes coupling is something we generally don’t want. Obviously having a plane roll when you wanted a yaw, or yaw when you wanted roll makes precision aerobatic flying more difficult. Knife Edge flying especially shows up any rudder coupling issues the model may have. A good designer of aerobatic plane will tweak things like the height of the wing and tail, dihedral angle and a bunch of other stuff in order to engineer out as much of this coupling as possible, but even on the best models there will always be some hint of coupling evident in some flying conditions. Modern transmitters with computerised mixes can tweak out the coupling that remains. For instance if when you apply right rudder in knife edge flight the plane rolls right and ‘tucks’ toward the belly then you would mix in some left aileron and some up elevator to come in along with the right rudder. If done correctly should see the plane tracking perfectly straight in knife edge. For adverse yaw coupling on aileron the usual trick is to set some differential so that the up-going aileron moves a little further than the down-going one. This can help make rolls a little more axial. Steve