The Dude II
Senior Heliman
Location: Martinsville, IN - USA
| kalps,
Been watching this thread.
How do you charge your batteries?
How do you load check the receiver battery?
Now the long story that will show human/equipment faults...that hopefully you & others will learn from and catch yourself before you have a model "get away".
Just yesterday I discovered a problem with an aging (maybe 2 seasons old) heavy duty charging line (18 gage & maybe 40" in length) I use to charge my receiver packs via a Triton charger.
On my.60-size planes I run just a 2000mAh NIMH with standard switch harnesses. On my Panteras and 1/4-scale I use Fromeco/Arizona setups and SmartFly.
The lead had developed high internal resistance (about 2 ohms...depending on how you wiggled it).
I discovered it when setting some CROW mixing functions on my plane while on the bench... when my servos slowed and throttle stopped responding (latter is Futaba PCM battery fail-safe mode).
I had just charged this model last Monday, flew it Tuesday...maybe 4 flights (about 28 minutes) and definitely transported with the switch in the off position...the battery usually lasts 8-10 flights in this planes setup.
The Battery was new as of 11-2007...I suggest dating your batteries when you put them in service.
Problem was I trusted the "results" I was getting from my Triton...when it topped off the battery... the displayed showed that it only needed 500mAh. After all, I had just flown this bird two weeks ago...and I ALWAYS charge before I fly...so I figured the pack had a pretty good charge left from the previous trip out to the field.
Now, I always carry a Hanger 9 tach/voltmeter that when testing voltage...places a 250mAh load across the battery.
This is enough load check for what I'm flying with these two 60-size planes...and my rule is STOP FLYING and recharge when the pack voltage hits 4.7 to 4.8 volts @ 250mA.
The other day...I never used it across 8 flights between 2 planes (sorry...no Pantera flights yet...been busy elsewhere in the hobby/life).
If I had, I MAY(hint) have seen the voltage dipping down from the 5.1 - 4.9 range I usually observe when I'm testing between flights and the support equipment is functioning to spec.
So, I go down the path of building a new "better" charging lead...I'm in the Audio/Video industry...so I cut off a 6' lead of 16 gage 4-conductor (nice oxygen free copper...made in the USA)speaker wire. Solder on my male/female adapters and place my gold-plated compression-fitting banana posts. This cable should serve me well for a few years!
I go to "cycle" the battery in question...sure enough...it's dead, Jim (for you StarTrek fans).
Whilst this was going on, I decided to update the switch harness on this bird...after all, this is the 4th season for it, it is my general purpose, always with me flyer and gets on average 3 flights per trip to the field...and it's show stopper! Just a Hanger-9 Ultra-stick 40...but packing a ST-61 with MACS silent pipe...can you say blazing fast and square loops that can break your neck just watching!!!
I pulled the standard switch harness, put on a known good/charged 4-cell NiMH and placed a 3-Amp load via the Triton through this STANDARD switch harness...the charger immediately shut-off because I had the low voltage cut-off set to 4.4.
Without the switch, the "known good" battery supplied 3-Amps at 4.62 Volts.
I placed heavier gage wire on this switch harness, removed the one extension (battery sits in the rear of the plane for CG)and retested. Now the switch harness will support a 3-Amp draw and voltage is above 4.5 volts under this load.
I started to feel better...caught a bad (hint...hint) charging lead that I had put all my model aviation trust in, made a better switch harness and now cycled 2/3 of my 2000 NiMH batteries.
Today:
It's 5AM local, time to re-install the battery & switch...then check Run-Ryder.
I decide to put one more load test on the switch and battery before re-installing in the plane...WTF...it won't support a 3-Amp load...and NOW I have the low-voltage cut-off set to 3.6 volts!
This is a new charging lead, switch with heavier gage wiring than previous and a battery that was cycled and topped off not 12 hours ago!
Grab the "known good" battery...put it in place of the battery dated 11-2007...what do you know...4.55 volts at 3-Amps!
I have/had a BAD Battery!!!
FYI...The battery dated 11-2007 took 2200mAh at a .5A rate just over 4 hours. Now, that looks about right. I decided to probe a bit further...put it back on the charger...observed voltage while charging @ .5Amp...over 6.44 volts...THATS TOO HIGH for a 4-cell NiMH...battery is definitely going in the recycle bucket!
Kalps,
The points to take away from this wordy dialog...
1. Know your battery/charging system.
Have a method of checking voltage while applying various current loads to "load test" the battery.
2. Standard switches...are...well..."standard".
Go invest in a Heavy Duty switch harness.
3. We've seen in the past 6-9 months that Spektrum receivers can suffer from "brown-outs". This brown-out can be prematurely brought on by:
a: bad or too small of gage wiring in a switch harness based upon the servo loads.
b: bad battery
c: battery not fully charged
d: battery not sized properly for the servo load.
You have an airframe in this heli that's capable...when you push it...to pull more current from your battery than a standard switch can handle.
One last note...have yet to see an ARF (heli or plane)that didn't have a "show-stopper" out-of-the-box. Best to go over 100% of the airframe before even thinking of taking it off the bench to the field.
Good luck!
it really tied the room together |
