How about the use of a capacitor with a Rx-compatible plug. Will it in any way be of benefit for a battery pack with a sour cell?

Holding full deflection will not do anything, it when the motors in the servo runs that you get a load on the battery, i.e. move all channels while looking at the voltwatch.

You would need a very, very large capacitor for that. A capacitor can however filter out the deepest voltage drops, and could prevent the RX from going into to safe-mode prematurely. A proper selection of capacitor will need an oscilloscope for analysis of the voltage supplied to the RX while moving the servos.

Good advice. I always make it a habit to check my batteries under a load. I had a pack that was charged to 7V at the house like yours, yet when I tested it under load, it plummeted like a rocket. Had I flown with it, probably wouldn't have come back down in one piece.

Turned out the pack had gone bad and wouldn't hold a charge. Checking it before my flight saved my plane.

That too is not necessarily true. Even an elevator can "bottom" out. But the most likely control to have problems with is the throttle. It's easy to set that up so that the servo trys to push the throttle beyond it's full open and full closed limits.

CGr.

Which is why I do not subscribe to the 6V 5cell packs = redundancy / safety net.A dead cell increases internal resistance of the battery. Two separate packs =

Bottom line best practices seems to be "do a voltage load test on your battery pack before a flight". It will identify whether your your pack (4.8 or 6.0) can hold voltage over a several second period. If it does then your flight will likely not be adversely affected by a faulty pack. No guarantees.

Thanks for your collective input - very good stuff indeed.

For sure, I agree with those who advocate a Volt watch or Voltmagic (for LiFe packs) to check voltage when sticks are moved.

WHAT LOAD ( .5,1, OR 2 )O YOU PUT ON THE BATTERY AND WHAT IS AN ACCEPTABLE VOLTAGE DROP WITH THE LOAD ???
     THANKS !!

Can Iask what kind of batteries are you all using?

NMH , 6V , 2000 MA

Ahh, most of you running nimh or nicads i'll bet.

4.8 or 6.0 - must be either NiMh or NiCd with 1.2 v per cell. LiPo or A123 have different per cell voltages.

Oh ok Iwasnt sure. I was wondering why everyone is going through all this trouble with load testers and volt watches. That's why I only run LiFe batteries. No problems.

LiFe are the A123s aren't they? I had a long conversation with the techs at a battery pack builder / distributor. He STRONGLY advised NOT to use the "iron" batteries for my application for various reasons that I can't recall to debate the pros and cons - I will leave to the guys in the Battery Forum.

A123 is a brand name. They are the best LiFe batteries you can get. Iknow of four other LiFe batt manufacturers, but never tried their stuff.

Thanks for clarification. Good to know about the quality.

Kinda off topic ...

Is there a quality rating for various battery manufacturers? If I had paid, let's say, 5$ a cell for the best one instead of $4 a cell for the cheap one I may still have a trainer to fly.

For Nickel based batteries, it's Sanyo all the way. They are significantly more expensive than the competition, but the quality is fairly obvious. They don't self discharge as quickly, they deliver more voltage under load, and they last longer. I realized the difference when I replaced my starter pack. I had built it out of Turnigy's first to be cheap, and it would hold a charge for about a week. The batteries had noticeably degraded in performance after about a year. I made a new one with Sanyos, and I have gone 3 weeks before with no noticeable self-discharge and it is still going strong after a year. The starter has more power too with the same cell type and voltage.

I made a loaded voltage tester from the instructions here http://www.hangtimes.com/a_loaded_digital_esv.html

It plugs into the plane and also into my DVM so I can watch the voltage change over a few seconds.

I should use it every flight but usually forget about it. Need to stop that!

I'm surprised no one here has mentioned battery cycling. I have an Accu-Cycle elite and I cycle all my Rx/Tx at least once a year. That way I know what each battery capacity is and how many minutes it takes to discharge. Once a battery drops below 75% capacity, I replace it. Cycling your batteries can also perk them up a bit and increase capacity.

At the beginning of last years flying season I charged up my Shrike 40 and Hitec over night before a day of flying. On the first flight of the day I was about 1-2 minutes into the flight and I hear a beeping from my transmitter. I looked down and saw "LOW BATT" on the display. Luckily for me I was able to land without incident but it taught me a lesson. Cycle and record battery capacities often! I found the Rx battery to have about 350mah capacity and the Tx batt had about a 40mah capacity. I credit my 72mhz system for holding up and bringing my airplane back, but that's another topic.

Cycling Batteries are a very good practice and Will give you an pretty accurate Measure of Flightime and Capacity Percentage...But I recently Bought an Aurora 9 Hitec Radio And It has Onboard Voltage measurements While You are Flying (Realtime) And If you have Battery Issues Or a Servo Fails Or a Linkage gets stuck and Starts Overdriving the Servos The Radio Warns You Starts Beeping when You have a Problem (Voltage related Drop) and Gives you a Heads Up!! It has Already Saved a Plane I would have Otherwise Lost.... Thanks Hitec ... Spectrum has Also Come out with a Telemetry Equipted Radio...It will Save your plane If you have a sudden voltage drop..... pretty cool stuff... My Voltmeter is always reading my plane ...

The Voltwatch is an "Expanded Scale Loaded Voltmeter". As others are trying to point out use your servos as the load and the Voltwatch as the expanded scale meter. Learn to watch how low the LED's dip during periods of high current draw, heavy load, and you can predict how much life is left in your battery. If this is not good enough for you, place a voltmeter in the system with the Voltwatchand document the voltage levels for each LED. I have designed and built my own version of a Voltwatch and I can assure they are nothing more than an expanded scale voltmeter.

nachman4859, I have a Hitec Eclipse 7 and it too has a Tx battery voltage readout on the display. Looks like Hitec went a step further with the Aurora 9 to monitor the Rx end as well. Cool! My Eclipse 7 saved my plane by beeping at me when the battery got low. Thank you Hitec!

BDZ65, I've been looking at those Voltwatch monitors for a while. I'd most likely get one for a complex airplane with higher current draw. But like I said, I cycle my batteries so I'm pretty confident when I go to the field to fly. The Accu Cycle Elite allows you to adjust the discharge rate and minimum voltage it will discharge the battery to. So you can customize it to your airplane's current draw requirements. It's just nice to know how many minutes it takes to deplete your battery to minimum voltage.

I could be wrong but from what I've been reading, the 2.4 systems out there seem to be more voltage sensitive. Rx batteries are critical with those systems as the Rx seems to reboot if the voltage drops below a certain level. 72mhz systems (I feel) are a bit more robust when it comes to low voltage situations.

Quickturn,
I agree with periodically load/ capacity testing battery packs,Imeasure the capacity of my packs at least 2x/ year, using a constant current discharger I built. I still feel the Voltwatch monitors are a great device and if used correctly can tell you a lot about battery condition while at the field.

That down link Telemetry is real cool stuff, defiantly the way of the future.