Bob Mitchell

I'm putting the finishing touches on my plane and hope to see it fly next week on training night. Battery questions:

1. My transmtter shows battery status in the LCD screen, but how do I monitor the status of the receiver battery?

2. I'm aware of some of the issues with NiCads from some of my early photography days. Can someone please educate me on battery "cyclers"? Can I cycle both the receiver and transmitter batteries with the same piece of equipment?

3. What about field chargers? I've seen reference to them and suppose they can be use to quickly recharge either the TX or RX batteries. Is this correct? There is a disclaimer in my transmitter manual that using a charger other tnan the one Futabe supplied may damage the batteries. Is this really a concern?

4. For 2 and 3 above: What is reasonable in terms of equipment (cost, abilities. etc.) and what is overkill? Any specific recommendations on equipment?

Thanks in advance.

Bob

DMcQuinn

My Feedback: (13)

(1) is your most important question. The receiver battery needs to be checked after about three flights. You buy an inexpensive "loaded voltmeter" also called "Expanded Scale Voltmeter" (ESV) - about $20. It is a voltmeter that puts about a 300 mA load on the pack. When this shows 4.4 volts you are done. You hook up your switch / charging harness such that the charging jack is external to the fuselage. This way you can check the voltage without removing the wing. Most receiver packs will give you at least 6 10 minute flights. But this is dependent upon the number of servos and how hard they are working. The servos use much more current if the surfaces are binding (e.g. hinges are stiff).

(2) NiCd's ares still used but they are not as common as they were 20 years ago. The whole issue of partially discharging causing a battery "memory" is largely unfounded. And there is no such problem with NiMh batteries or Lith-Polymer or Li-Ion or LI-Fe. I would not worry about it. Just charge your packs up with the provided charger for 10 hours the night before you fly. There is a value in owning a "cycler". You want to test your battery capacity about every 6 months. So you charge it up, and then discharge it using your "cycler". The cycler measures how much current flows out of the pack until it falls below some low-voltage cut-off (e.g. 4.0 volts). If the batery has a capacity of 600 mA when new, you will find that after several years, it will show less capacity. If it gets down to 80% of the original, then it may be tinme to buy a new pack.

(3) Field chargers are generally not needed and are hard on batteries. They much prefer to be slow-charged with the wall-wart charger. However, if you fly more than 6 flights per day, you may need a field charger. Buy one that has a cycler in it and you will have two devices in one unit.

(4) About $100 will get you a nice charger / discharger. Then you will need a 12 Volt battery to drive the field charger. You can use your car battery if you park close to the flight line.

Missileman

1. I differ from DMcQuinn in that you should check your battery EVERY flight. Just because in normal conditions you can easily get 3 flights from a fully charged battery stuff happens, didn't charge all the way, lost a cell after the first flight ect....
There is hot debate on the use of Voltwatch onboard battery monitors, I use them and they serve their purpose. Expanded scale voltmeter is more accurate but you have to remember to use it.
2. Cycling is not as important as it used to be but can rejuvinate a battery that is starting to lose some capacity. I use an Accu-Cyle charger that charges/ cycles both transmitter and receiver batteries But you can't discharge most transmitter batteries without removing the battery because of a diode in the transmitter.The Accu-Cycle I use is $63 at Tower Hobbies
http://www3.towerhobbies.com/cgi-bin...&I=LXL357&P=ML
3. Field charging is a personal choice. I put a 2,000mah battery in my transmitter and 1500 to 2000mah batteries in my airplanes. I charge at home and can fly all weekend without re-charging. I do have a good field charger just because I needed a good lipo charger. It is a Bantam E-station BC5. The BC5 was $125 but again I bought it for its ability to balance charge lipo batteries iy is just an added bonus that it will charge all my other batteries including my 12V gel-cell field box battery.
http://www.grandrc.com/inc/sdetail/66739

Jetdesign

My Feedback: (8)

I was wondering about upgrading the batteries that came with my Futaba 6EX, both for the transmitter and receiver (increasing the mah's). Anyone know how to go about doing this, and can recommend a good place to get batteries? The manual says you can get three 15 min. flights on a full charge, then has to be recharged for quite a while. I can really see my tx battery go down while I fly on my sim, and while playing around with the trims and stuff. I'd rather have some long lasting batteries that I can charge overnight at home, and not have to worry about charging at the field, and would like to be able to get in more than 3 flights in a day.

DMcQuinn

My Feedback: (13)

FatOrange - my experience is that a 600 mA battery will give 90 minutes of use on the transmitter. I'm surprised that Futaba says only 45 minutes. ANyway, the upgrade is pretty simple and not too much cost. I like www.radicalrc.com. You can get transmitter packs with three or 4 times the capacity as the factory original.

Jetdesign

My Feedback: (8)

Will any 4.8 volt battery with the right connector work well in the plane (and 9.6 volt for tx)? And obviously just look for one with higher mah's.

Jetdesign

My Feedback: (8)

Will any 4.8 volt battery with the right connector work well in the plane (and 9.6 volt for tx)? Is it OK to switch from AA to subC? What about changing from NiCd to NimH?
Geez, thanks for that link...I can triple my flight time for $20?!

CGRetired

My Feedback: (1)

There is more to a battery pack than just batteries. The way that the manufacturer bonds the cells is very important. The reason for this is that the vibration in the RC aircraft is pretty high which can cause poorly constructed packs to come un-bonded resulting in an open battery pack.. and you should be able to figure out what happens next.

Regarding checking battery packs frequently during a flying day, I told a story, actually a few times here on RCU, about my Venus II, which is a 90 size pattern plane. I have a pair of 1200mah NiMH packs in this plane. I operate them in parallel, each having its own switch and going to a separate channel on the RX. I also use Voltwatch on the Venus II. After two flights one day, and after checking the battery pack before and after each flight as I preach.. I had checked the battery packs (both.. the method is simple.. turn both off, then turn one on, check it, turn it off and then turn the second on and check it).

I checked both packs before the second flight, and all was fine. I flew for about 10 - 12 minutes, then landed. After carrying the plane back to the bench, I did my routine.. checked the battery packs again.. as I said, before AND AFTER each flight. When I checked the voltwatch, which monitors the packs, I found pack #1 in the green, and then pack #2 in the RED!!! So, I checked them both with an ESV. One read 6.1 volts, and the other read 1 volt, then the display on the ESV flashed a few times. I was totally surprized and thought that my ESV was bad, so I borrowed someone else's ESV and it read the same thing.

I removed that second battery pack and checked it again.. same thing. Fortunately, I had a spare battery pack, so I put it in the Venus II and recharged both batteries to make them both the same.

The voltwatch and my practice of checking battery voltages before and after each flight saved my plane. AND, what's applicable here is that the battery failed in flight. Checking after three or four flights would have resulted in a crash.

CGr.

Rufcut

You absolutely want to check receiver voltage after EVERY flight. That is still no guarantee that the battery will not fail in flight but it is about the best you can do to ensure that you're good to go. My receiver battery went south between flights this winter. I had just checked it with the ESV and it was around 4.9 v. I was just lining up for takeoff when my horses got loose in the field I was using and I had to shut down to get them back in the paddock. When I came back ( about 15 minutes) I switched the receiver on and........nothing. The battery had gone dead just sitting there. I don't like to think what would have happened if I had gotten off the ground. After that I installed a back-up battery as CGRetired described for a little extra peace of mind.
As a side note, when I took the bad batteries to Radio Shack for recycling the owner thought that thermal shock might have caused it to fail. Anybody heard of that?

Rufcut

Jetdesign

My Feedback: (8)

I was looking at batteries from RadicalRC, so I imagine that the bonding should be fine; they're rated for aircraft use.

I have a voltwatch built into my plane, so I plan on checking batteries every flight, too. I'm just surprised at how fast both the Tx and Rx batteries lose their charge, but then again, they are only 600mah. I have a small car, and also like to consolidate, so getting new Tx and Rx batteries w/ more capacity just seems to make sense.

But what about switching from AA => subC? And Nicd to Nimh? Does that matter?

Missileman

These are the receiver batteries I use 2,000mah 4.8V with a U connector (start buying everything with U connectors, U=universal and will work with any brand)
http://www3.towerhobbies.com/cgi-bin...&I=LXNRH6&P=ML
All-Battery.com has transmitter batteries 2300mah for $16, I don't know how good they are but I have bought other batteries from them in the past with good results.
http://www.all-battery.com/index.asp...S&Category=165
Switching to Sub C or NiMh doesn't matter except Sub C will be heavier and really no benifit. NiMh in AA is plenty.

-pkh-

My Feedback: (2)

Install a Voltwatch battery monitor on your plane to monitor your receiver battery:
http://www3.towerhobbies.com/cgi-bin...&I=LXHDJ2&P=ML

Yes, there are charger/cyclers that can do both RX and TX batteries.

Yes, you can quick charge your RX and TX batteries at the field if you wish. However, this does reduce the service life of your batteries. You must monitor the battery temperature to be sure they don't overheat.

Here are two good multipurpose chargers that will serve as field chargers and battery cyclers. Note that the first one (Super Brain 977) comes with a 12V power supply, while the other does not (you have to buy your own power supply or use a 12V car battery):
http://www3.towerhobbies.com/cgi-bin...&I=LXLCJ6&P=ML
http://www3.towerhobbies.com/cgi-bin...?&I=LXMAJ0&P=7

Bern

My Feedback: (17)

Hi Bob,

While NiCds are still sold there are better batteries available today. NiMH are more powerful in
the same size cells and they do not have to be cycled as they have no memory.

The charger that came with your radio will charge the packs overnight. Use a meter that you can plug into you charge port on the plane. Here you can read the Rx pack. There are several good field chargers on the market. If you would like to get more information please contact me at my email address. [email protected]. Here I will tell you a lot more of what you want to know.

Bern

Jetdesign

My Feedback: (8)

Missileman, can I use the same charger that came with my radio to charge those batteries (i.e. will a Nicd charger charge Nimh)? What an amazing deal for those batteries!

Missileman

I have had no problems charging NiMh with a wallwart charger but it will take alot longer.
Divide the capacity of the battery by the charge rate of your charger, should be printed on it.
That is of course starting from a nearly dead battery, if your battery is already half charged it will take half that time.
At some point you will want a better charger but all in good time.

TWD

Hi,

I am new to electric flight. Been flying RC airplanes (gas power) for 20 years. My question is: I have a 9.6 volt 650 mAh NiMH battery pack that is very hot after a flight (185 degree F) Is it common for these batteries to be this hot after the flight. Any input would be appreciated.

Thank you,

TWD

TWD

Hi,

I may not have given enough information about my hot NiMH battery pack. The hot battery in question came out of a Gurnli A-10 airplane. This jet is powered with 2 GL5030 ducted fan jets using (1) 40A ESC. The plane has 3 micro servos for controls.

Thank you for your help.

TWD

TWD

It's Me,

Sorry! But I have more information about my NiMH battery pack. I just ran the battery outside of the plane so it would have some cooling. I ran the two fans only with this pack (approx. 4 to 5 min) the battery temp. got up to 215 degree F. Is this normal operating temp for these batteries? Do I need to start looking for other possible problems?

Thank you for your help!

TWD

AstroDad

I think using two batteries in parallel is very cheap insurance and a very good idea. I have the exact same set-up on my planes. On my 40-size I have a pair of 750 mAh NiMH packs and the Voltwatch. I have never managed to run them down. I would guess they would easily last for 3 or 4 hours of flying, maybe much more.

The extra switch, extra battery, and Voltwatch should only cost about $40

Missileman

Yes they do get hot and sadly it is not good for the battery. Upgrades on battery, ESC and Motor will help but throttle management will help also.
These planes are really not suppose to be ran at full throttle all the time but some of these cheaper RTF planes are so under powered you haven't got much choice.

TWD

Thanks Missileman,

This plane only cost about $100.00 I just hate putting another $150.00 to $200.00 into this plane! Guess I will just try and get more cooling to the battery and fly it the way it is. Get it into the air ASAP, cut the throttle back just enough to keep it flying and see how that works. If a temp. from 180 to 215 degree F. is the norm I will just live with it. In general do NiMH batteries tend to run hotter than Nicd? Thanks again for you help.

TWD

Rodney

Your 6EX transmitter batteries that came with the unit will easily give you at least 2 and 1/2 hours of use. The indicated voltage shown on the LCD will fall to about 9.4/9.3 volts after about 45 minutes and hold above 9.2 volts for another hour easily. It is perfectly safe to fly until the voltage fall to 9.1 volts (about 2 hours and 45 minutes) if starting with a fully charged battery. In fact you can fly down to 8.9 volts (3 hours) safely and still have plenty power to operate your transmitter. Now the receiver is another story, depends on how many servos and how you fly. The suggestion to put a Voltwatch on your plane is an excellent one; IMHO much better than a loaded voltmeter as (if you check after each flight before turning off either the transmitter or receiver, your readings will reflect the actual loads you have been experiencing in flight.
As to batteries, if you have adequate space and weight carrying capacity, stick with NiCads as they are much better than NiMh in all respects except for size for equivalent capacity plus are much more tolerant of abuse such as minor overcharge and heat plus will last for twice as many charge/recharge cycles. In the way we use them in RC, they are no more apt to have any memory problems than the NiMh. For all but the most stringent weight requirements, NiCad still rule the roost.

Gray Beard

My Feedback: (-1)

Anymore I use NIMH batteries for the most part but if/when I can find them I like the NICAD. Just because they take the heat of fast charging better. GA, I almost always get the biggest packs I can but sometimes I have batteries standing in line waiting for A charger that will charge them all the way. I have three chargers plus my fast field charger.
I love my old Ace DIGIPULSE because I can charge 6 batteries all with different mAh requirements but it only goes up to 1500 mAh before it goes into trickle mode. My Accu Cycle was OK as A charger but it never did work very well as A discharger, sent it back but was told it was OK, so much for Tower junk. I then bought the H-9 Sure Cycle, outstanding machine does the TX and RX batteries at the same time. Because I fly so many different planes and used to fly big events for several days at A time I also have the H-9 Double Vision Fast Field Charger. I have it set up to plug into any cigarette lighter or computer auto outlet.
My flight packs also vary. I mostly have 6 volt NIMS running about 2500 mAh but i also have some big 6 volt 4200 mAh NIMs in Sub -C with two wires. On some of my bigger planes I needed the weight so the Sub-Cs, I have also had switch problems in the past so the two wires for double switches. I have run the redundent two battery systems and like it but it depends on my plane. For GAs up and comming new pattern plane the two 6 volt two switch system is over kill but could be A good idea, could also be A 4.8 volt system too. i I also have two battery testers in my flight box most the time, I do use volt watch on some planes or the GEM 2000 but I still test before each flight even if the VW is stating good!!

TWD

I am sure happy I am not the only one holding on to using Nicads & NiMh flight batteries! I was a little worried about how hot the NiMh batteries got after a flight, but everyone has been telling me thats the way they are. Thanks to you all for your in put. Keep the information flowing!

opjose

I picked up four TX "Rhino" battery packs from Unitedhobbies.com aka HobbyCity.com.

They are rated at 2750mAh and feature both JR and Futaba connectors.

Cost about $18.00.

I've been using them for several weeks. Typically I charge my TX's on Friday and don't worry about them over the weekend....

My timer indicates that I've had the TX on for well over 12 hours w/o even dropping to the first tick mark for normal NiCD/NiMH batteries.

I keep my now "old" 1800mAh TX packs charged up as spares...


I've been quite impressed with their Zippy and Rhino series.

I've purchased four 3700mAh 20/30C 14.8v LiPo packs for about $68.00/ea.

They test out around 3850mA and do not get warm when discharged at 20C.


I've also seen several US vendors selling similiar TX packs.