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Motor / Battery Short Flying Time

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Allan Bowker11/03/2009 01:53:32
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I have a "Wild Hawk plane" also known as a "Merlin Condor" and is a cheap copy of the Multiplex EasyStar.
 
 
On a fresh fully charged battery I'm getting about 1 minute on full throttle before the motor stops (although the servo's are still fully operational).
 
Surely it should last longer than this?
 
Motor: 380 - standard stock motor
Prop: Gunther Electric Push Prop (LINK TO PROP)
Battery: 7 Cell 8.4v 1000mAh Ni-Mh - (1300mAh Ni-Mh supplied as stock)
ESC: unknown - standard stock ESC
RX: Spektrum AR500 (upgraded from stock 35mhz rx)
Charger: Fusion Elysium LX60B (as recommended by RCM&E)
Battery charged at 0.8A
 
What do you think? 
Would a 1300mAh battery make much difference?
Is the Spektrum RX that I put in there having an effect?
Is this battery unable to drive the 380 motor for sustained periods?
Charging / Battery problem?
Do I have a different problem?
 
I feel like replacing the whole power train (motor, battery, esc) as it does seem a bit under powered but can't afford that at the moment (I think it would cost me £60).
Help everyone please!


ken anderson.11/03/2009 07:03:54
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hello allan-try brc-you might be surprised at the cost-to replace your motor if t's only a 380-i reckon a brushless motor and controller could be had for about £20...£30 .00 that'll solve your problem................ what you have at the min look's low spec/poor combination............
 
              ken anderson....................
Tim Hooper11/03/2009 07:06:28
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I'm wondering how many cycles the battery pack has had so far.
 
If's a brand new pack, then a trickle charge at around 100ma for around 14 hours or so should get it all topped up and balanced.
 
Secondly, I've always been in the habit of 'topping off' the cell pack just prior to use.  1amp until your charger cuts out, just before flight - especially if the pack has been standing idle for a few hours or so.
 
tim
ken anderson.11/03/2009 07:26:02
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hello allan-had a quick look on brc's site---check out the link above..........
 
               ken anderson.
Allan Bowker11/03/2009 07:49:22
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Thanks Ken, certainly worth the money it seems
Tim Mackey11/03/2009 10:09:36
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Lets look at all your Qs and give some answers Allan.
1) No
2) No
3) Obviously yes in your case - but it should be fine.
4) Quite possibly
6) Maybe, but until we eliminate the others its hard to say really.
 
I would tend to think that its a battery / charge problem. Tim's idea is sound.
Of course, it could be just that the battery  / cell is goosed from over-use, or previous bad charging regime. You dont say how old the battery is.
Have you measured the voltage of the pack fresh off the cooker - and also how much goes back in ( m/a ) after a re-charge?
I have assumed that the original battery suplied was the same cell count (7)  and not 8?
 
Allan Bowker11/03/2009 12:37:54
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What battery would I use with that BRC hobbies set? The ones I already have?
 
I keep a log of how many times my batteries are charged and without checking the log, these batteries have been used about 10 times each. I purchased 2 of these 7 cell 8.4v 1000mAh Ni-Mh batteries at the same time 2 months ago from my local model shop.
 
I'm hoping that my charging regime is not considered bad.
When I get home from a quick fly over the park I charge both batteries and they are stored at room temperature (charged, not cycled). Before going out I top up both batteries and then repeat... (I charge them at 0.8A rate)
 
I will have to get back to you on the voltages fresh off the cooker. I will try a cycle tonight (1.0A discharge & 0.8A charge) and report back with times and voltages.
 
The Wild Hawk is supplied with a 7 cell 8.4v 1300mAh battery, however I purchased this plane second hand and didn't get the original battery pack. All I had was the plane, motor & ESC. I had to source and fit my own RX & battery.
Tim Mackey11/03/2009 16:51:37
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Charge routine sounds fine - assume that the charger is designed for NiMHs of course?
You could use the existing batteries with the proposed brushless setup - but TBH pretty much everyone these days uses LiPo - have you any provision for dealing with LIpo?
Apart from the extra power ( even a 2s LiPo will be as good as or more powerful than 7 NiMHs )  the reduced weight will help a lot with P/W ratio too.
 
ken anderson.11/03/2009 20:02:43
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allan-3 year's ago i started with brushed motor's with nicad's-then brushless with nicad's--then brushless with lipo's---2200/20c-excellent value at £22.00---you'll be gobsmacked at the performance/duration etc--you can't take it with you-your only here once etc....................
 
           ken anderson.....
Allan Bowker11/03/2009 22:17:27
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Thanks guys I think you are right about upgrading the motor, esc, battery.
 
I have a few Li-Po's for my blade CX2 but I think I may be better off buying another few Li-Po's for this plane.
 
I hate to be beaten however with the current setup.
( Fusion Elysium LX60B charger )
The charger was given an excellent recommendation in RCM&E Oct 2008 issue.
Page 98 and is designed for pretty much any battery too. Article by David Ashby.
 
The battery has just finished charging.
Discharged to 5.5v after 20min @ 1A
Then charged to 9v fresh off the cooker in 9min 6sec.
Charged @ 0.8A - I don't think this right, surely should have taken longer?
The delta peak is currently set at 4mV per cell by default. Not sure if this is OK?
 
Any more suggestions guys? Thanks.
 
 
 
 
 
Tim Mackey11/03/2009 22:28:18
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Delta peak sounds about right for NiMHs but there is definately something wrong here. 
7 cells should peak at around 10.5V minimum.

At .8 A ( 800ma) the 1000ma pack should take at least 1.5hrs allowing for charger inefficiencies
I suspect it is peaking too early.... try adjusting the peak detect value up a bit
Allan Bowker11/03/2009 23:13:18
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OK, thanks Timbo - I have edited the post above and put lots of useful links in there for anyone to reference.
 
I have adjusted the delta peak to 8mV per cell and started the charge from where it left off.
As far as I know I should be OK doing this without a discharge cycle first.
 
[...goes away and plays on RealFlight G4.5 while waiting for the charger to do it's job...]
 
beep...beep...beep
 
Chargers just finished. It took 33min 39sec and is reading 9.9v
At least the battery is getting warm now.
 
I think I will try the other identical battery now and see how that goes.
 
Just looked at the battery log and they have both been charged 9 times now, including tonights charge.
Tim Mackey11/03/2009 23:22:50
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Warm is fine...but HOT is not!
If the packs actually get too hot, they will be permanently goosed.
I think you should try a discharge /charge cycle, with a DP value of around 6mv, measure and log how much went back in from "flat" ( discharge to 1V per cell )
Allan Bowker11/03/2009 23:46:54
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Yes, battery was toasty warm, not red hot.
 
Second battery is currently discharging @ 1A and has been discharging for 20mins so far.
 
I'm guessing 'DP value' is "Delta Peak".
 
It is currently set to the 8mV that you said before, however I will stop the discharge now and set the DP to 6mV and restart the D>C (discharge>charge) cycle.
 
Q: I can't set the discharge value to 1v per cell, only as an overall battery voltage.
So should I set it to 1v or 7v ??? (7 cell battery)
 
I will log and post the results. I will be glad when I have the hang of this elastic trickery stuff, IC is soooo much easier.
Allan Bowker12/03/2009 00:19:06
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Timbo / Ken
 
Battery stopped charging at 5min 40sec @ 8.5v straight off the cooker and down to 8v within 2 mins.
0.8A charge rate with 6mV DP - battery is barely luke warm, only just over room temp.
 
I can't set the discharge value to 1v per cell, only as an overall battery voltage.
So should I set the didcharge target voltage to 1v or 7v ??? (7 cell battery)
 
I'm guessing your going to get me to change the DP value again?
 
ken anderson.12/03/2009 07:57:26
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allan-put a different charger on the shopping list this is the one i,m using-had it for a while-user friendly etc.....
 
 
 ken anderson....................
Tim Mackey12/03/2009 09:02:44
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Hi Allan - to discharge down to 1V per cell, in a 7 cell pack set it to 7V
Ken.... it seems a bit flippant ( and I am sure you dont mean to be ) to suggest  discarding a brand new charger that  he has purchased following a recommendation in the mag.
The problem is more likely to be the battery / finding the appropriate settings.
ken anderson.12/03/2009 09:20:53
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hello tim and allan---all respect to you both-informing allan only of what i was using--i'm not on the book's/ commission etc--as reguard's what a mag recommend's-is another thread on it's own............
 
              ken anderson............... 
Allan Bowker12/03/2009 10:19:46
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OK, thanks guys. 
 
I just need your views on what I should set the DP value to now.
Tim Mackey12/03/2009 10:26:32
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Try 6mv per cell ( not sure if that particualr charger set sthe cell count from when you input the battery voltage required ? ) Some do, some do not. If not, then obviously you would set it to 6 X 7 = 42mv.

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