markhamregular

Where can I find tips about flight pack batteries? My 72 Futaba came with a 700mamps battery. It isnew but is not giving me more than 2 to 3 flights after a full 14 hours charge. Someone suggested at the field that I fully discharge it before I charge. Will that help? And if so, how do I discharge completely? The manual has almost no information or tips for flight pack batteries. Thanks.

Phoenixangel

That type of discharge/charge is called cycling. There are a lot of chargers that will do this for you and you.

Yes it will likely help to cycle it, but a new battery should be in decent shape. Cycling will also help you to see the true state of the battery pack. Most cycle chargers display exactly how much power they pull out and put back into a battery.

There are other ways to fully discharge a battery, like simply leaving it on until the device shuts down, turn it off wait 10 minutes and turn it back on. Do this 4 or five times and the battery will finally actually be discharged. I would not really recommend it tho.

I have a few chargers, to many in fact. My favorite at the field is http://www3.towerhobbies.com/cgi-bin...?&I=LXEYD4&P=0. It is fantastic. I have another one that I use a LOT for different things as well. http://www3.towerhobbies.com/cgi-bin...?&I=LXMAJ0&P=0

There is a ton of stuff about your battery type here http://www.camlight.com/techinfo/techtips.html Hope it helps !

Oberst

Phoenixangel is right.

If you don't have anything to cycle your battery and check it's condition, someone at your Club will. (If you belong to a Club) I have a friend of mine that only operates electric planes and he has all the gadgets. He was nice enough to have cycled my old transmitter battery last summer. The transmitter battery is like new again and I use it as a back up.

Are you charging your batteries for at least 16- 18 hrs with your stock charger? That could also be the reason why your charge doesn't last- your batteries aren't getting a sufficient charge.

Another thing you can do is get a larger battery. I have a Expert Electronics Pro 1500 mAh in my JR ProPo SX600 and charge it 24 hrs before flight. My transmitter came with a 700mAh battery as well, but it only lasted for about 4-6 flights. My 1500 mAh can last about 8-10 flights. I needed a bigger battery because I fly up 1-4 planes one one transmitter.


Pete

Square Nozzle

My Feedback: (1)

Don't ever discharge your batteries until they are flat out of voltage. That's the best way to ruin a pack. Cycling involves bringing the voltage down to a set value (1.1 volts per cell is typical for NiCads and NiMH cells) then recharging to full charge. The battery pack will be warm to the touch when it's fully charged. A wall wart charger like what's supplied with your radio will not do that. If you want the best advice on battery care, go to Hangtimes Hobbies - NoBS Batteries and open the link to Red's R/C Battery Clinic. You'll learn the correct way to treat your batteries. Reputable battery suppliers will always advise you to cycle new packs to get the most life from your pack.

Gray Beard

My Feedback: (-1)

My little 700mah futaba battery lasted me so many years I can't even recall how long it lasted. I did replace it finally this year, so 8 or 9 years. Cycling is a must do thing to get the battery to charge to full capacity. When I first started in RC I would turn on my radio and plane then just sit and watch TV while moving the sticks to discharge. It must have worked. Then I bought a charger that would cycle and life became easier. The new packs seem to take about 4 cycles before they will take a charge to full capacity. Once you get them there your TX will last a bunch longer. Like most people I now have several chargers of different types. They seem to come with the years.

HighPlains

My Feedback: (1)

Harry,

How are you deciding the battery only has power for two or three flights?

What is your airborne setup? Number and types of servos.

markhamregular

I have 4 servos. My instructor told me that 4.78 should bethe minimum.
Today after only 2 six minutes flights, the battery was already 4.8
That was after a 14 hours charge

Gray Beard

My Feedback: (-1)

My bad, I had a brain fart and was thinking TX battery, you said flight pack. My flight packs still last me a couple years, I just tossed one I caught that was bad. I had installed that pack in 04. Without a cycler I wouldn't have know it was bad until after the crash. It took a full charge but would only cycle down about 300mah before it started charging again. It was a 1200 mah pack. Your instructor probably has a charger that will cycle. Ask him to cycle it a few times for you. Wall wart chargers that come with your radio take about 24 hours to really give your pack a full charge. Some are better then others and really will do what they call an over night charge, some don't. A good charger is one of those tools you will use a lot so give some thought into getting one. I have five or 6 chargers and they get used a lot, some of mine are better then some of my others. I'm not a big fan of anything that says Hobbico on them. Other guys love them. The one I have is junk as a cycler but it charges OK.

speedracerntrixie

My Feedback: (29)

Harry, it sounds to me like your airplane is consuming too much current. Check all the control surfaces to make sure there is no binding. The surfaces should move as freely as possible. The best way to check is to remove the servo arm and give the pushrod a pull and push. The most common servo to be overworked is the throttle. It is pretty easy to either have the servo pushing on the linkage past full throttle thus stalling the servo and pulling lots of current. The same applies at idle. If you are setting your idle by using the idle stop screw you could be stalling the servo there too.

Steve Percifield

My Feedback: (14)

Number 1, how old is this battery? number 2, 14 hours is not enough charge if using the wall charger that came with the system. Put it on charge and leave it for 24 hours. Then let some one who knows what they are doing cycle it for you. The battery just might be weak and need replacing, but do the cycle thing first, at least 4 times and make sure you fully charge the battery.

HighPlains

My Feedback: (1)

Well Harry, your instructor doesn't know what he is talking about. The nominal voltage of a 4 cell NiCad pack is 4.8 Volts. All you have used up to that point is the peak voltage that they put out until they get into their working voltage. Tested under load the NiCad is in it's rated output from 1.1 Volts up to 1.2 Volts per cell. On either end of this more or less straight line is the initial charge that can show around 1.32-.34 Volts when freshly off the charger, and at the other extreme is the "knee" where the output voltage drops off the cliff at about 1.07 Volts. Stay away from this end of the discharge curve.

To allow for plenty of margin (a couple of flights worth) stop flying when you get down to 4.6 Volts when under load (300mAh). If you have a standard sport model (40-60 size) with only 4 non digital servos, you should easily fly for an hour or so. Six ten minute flights easily.

HighPlains

My Feedback: (1)

To make this easy to understand look at this web site:

http://shdesigns.org/batts/battcyc.html

The amount of power you are using corresponds to the first 18-20% of the batteries capacity. The discharge curve then becomes very flat until you get over to the far right side where the knee starts to show the end of useful power.

Valve floater

edit

markhamregular

I have 5 standard 3004 servos in my Big Stick. I found out that the one for the front wheel and rudder was a little hard but I use it only on take off. I think my biggest problem was giving 12 to 14 hours. Apparently, those chargers provided with the radio would require much more. I will try 24 hours. I may have to buy a charger-discharger first and if the battery does not give me 4 to 5 flights, then I wil buy one with more amps. Any suggestion for a AC charger-discharger at a reasonable price? Someone at the field this morning suggested a Venom.

Highplains, you suggest that 4.6 is fine?

Thanks,

markhamregular

I forgot to mention that after a 14 hour charge, the battery went up to 5.27 volts. Without using it, 12 hours later it was at 5.10 (loosing about 3.5%). Is that normal?

However, when I fly it, after two 10 minutes flights, it was already at 4.8 volts which according to my instructor is unsafe to fly.

markhamregular

Highplains,

So I see that the longest time is between 4.9 and 4.70. So, I should not be afraid when it's around 4.80.

HighPlains

My Feedback: (1)

Yes, all batteries have a bit of self discharge. A reading just off of the charger gives a false value. Remember, these cells are rated at 1.2 Volts, and you get 1.32 V for a very short interval of use. That trait is shown in the graph.

That is correct. When I have an airplane that I have flown a lot, and am very familiar with the power requirements of the radio, I have used the battery as far down as 4.5 Volts. But I am monitoring the battery very closely with a load and digital voltmeter, and know my current demand and time I can support it. Part of it is perhaps that I have flown RC since 1970 and have a degree in electrical engineering.

You can also chart your battery and make a graph similar to that on the web site. Just takes a load resistor, digital voltmeter, and a clock. I'd take a reading every minute for the first 5, then every 5 minutes from then on. If you are running analog servos use a load of around 300 mAh, if digital then around 500 mAh. Really just a resistor value of 16 Ohm for 300, and 10 Ohm for 500. Use resistors rated at 5 Watts to make your load. Take it with you to test at the field with the voltmeter. Compare your reading with your chart and you then know exactly what is left in the battery pack. Do it before every flight.

Finally, you mentioned that the rudder linkage is a bit stiff. Fix that, because if the servo is stalling or dragging, that will use up a lot of current.