How should I properly charge and discharge my Futaba receiver and transmitter batteries? I only fly about 3 flights a week, all on the same day. Other than that, there is the testing I do at home, maybe one night a week. After all of this, my transmitter battery is rarely below 10v and my receiver battery is rarely below 80%. However, I always charge them both overnight the night before flying, just to be safe. I heard that 3 10 minute flights would be the max that you would want to do before recharging the receiver, however I still show 80% after three flights.

Since I'm never fully discharging them, I thought I should probably do that, and have been leaving both on overnight one night a week to drain them. Sometimes I leave the plane on while I use RealFight, that drains the battery, but probably not good for the hardware to be needlessly worked.

Is this a good thing to be doing? Should these batteries be fully discharged once in a while? If not what should I be doing?

Also, I was given a 12v gel cell for my flight kit, and I bought a hobbico charger for it. The instructions say to monitor the charge with a volt meter. How exactly do I do that? Some of my questions above pertain to this as well... do I fully discharge it perodicly? It currently reads 12v on my voltmeter, at what level should it be recharged? What happens if I leave it on the charger to long? I don't exactly have time to sit and keep an eye on the volt meter.

Thanks again for your patience with my dumb newb questions, one day hopefully I'll know a thing or two about this stuff.

The need to cycle nicad batteries is often over stated. The best source of information on charging batteries I've ever found is at Red's R/C Battery Clinic: http://www.rcbatteryclinic.com/ . I've found it's better for people to read through his material, there's lots of great stuff, than to try to condense it and miss something.

One comment on something you said, discharging your batteries by leaving the receiver or transmitter on overnight is not a good thing. This could easily damage the battery pack.

i agree don't leave it on over night to discharge. the lowest you might want to go is 1.1v a cell. if you discharge too far you could set yourself up for thermal runaway///where a cell reverses polarity and well its a mess with heat.
good luck

Never completely discharge a Nicad! I've always found enough capacity in my battery packs to fly for around 1 1/2 hours, after being freshly-fully charged. This is an average time and not written in blood. Piper has given you good advice!

Nicads can develop what is termed "memory". This might happen if like you say, you consistently fly 3 ten minute flights and re-charge. The battery develops a memory and will develop a memory allowing a discharge of 30 only minutes.

It is very good for Nicads to be "Cycled". Cycling is discharging down to a specific voltage and recharged to their maximum capacity. I used to have a unit called a Super Cycle. It would discharge the 4.8 volt receiver pack and 9.6 volt transmitter pack down to a specific voltage and keep track of how long this discharge time lasted. Then the Super Cycle would flip to charge and charge the packs back to maximum capacity. I now have a unit called a Sure Cycle built by Hanger 9. This unit discharges and recharges, but, does not keep track of time. Instead it keeps track of the amount of milliamps used and keeps track of the charge time. I wish I would have held onto my Super Cycle!

Does anyone know of a cycler which keeps track of discharge time?

The accucycle elite keeps track of several things as it's discharging. I know it does mah, not sure about time.

Also be careful using any type of discharger on a Futaba TX. Some models have a diode in them that if you use a discharger while the battery is in the TX then you will blow out the diode and then you'll need to send the radio in to get it fixed.

I had this happen to a customer at the LHS I work part time for. I sold him the Hobbico Elite because he wanted a decent chager/discharger but never asked about the TX. He came back the next day and said this was a known issue with certain Futaba's. I cannot remember the model it was, but it was not that old. So check first.

I've done this succesfully with both the 6102 and 9303 JR TX's

ashly95, I'm afraid you have been missinformed as to reverse charging due to to deep a dischargc resulting in heat, it just doesn't happen. It may ruin the battery by decreasing its ability to be recharged, but no heat. It also does not hurt a NiCad to be completely discharged to zero volts, in fact that is how individual cells can be tested for possible internal shorts; you discharge it to zero thru some resistance to limit current then remove the load. If the voltage immediately rebounds (open circuit) to .9 volts or greater, the cell is good. You do not want to reverse charge it though as that may ruin it. That is the reason for many saying to not discharge below 0.9 volts per cell. The keeps the possibility of the better cells reverse charging the weakest cell in the link near the end of the discharge cycle. As long as you never let the cell reverse charge, no harm is done discharging to near zero volts.

I alway pull my Tx battery and charge it out of the radio. If I mess up a battery, 20 bucks. If I mess up my radio, well it cost a lot more than $20.

Hmmm, I need to look into this. Everything I've read says the diode prevents discharging. On the few occasions that I actually cycle my Tx battery pack, I pull it out of the transmitter.

Hi!
Forget about discharging!
Just charge!
And a some tips...do use NiMh cells instead of NiCad:s.
I use eight 2800 mAh GP cells in my JR 388X transmitter. They are the same size as ordinary AA (R6) NiCad:s.

Regards!
Jan K
Sweden

Chuck,

It's my understanding that it is not on every Futaba. For the life of me I just cannot remember the one I am refering too. I know it wasn't one of the higher end versions. The guy is a great guy but flies mainly low wing sport planes using mainly 4 - 5 channels

Both of my recent Futabas, 4YF and 6EXA have a diode. I know it prevents discharging from the charge jack. It also prevents checking the voltage from the charge jack. I'll try searching the Futaba site to see if I can find which model might actually get damaged.

I'm not aware of any Futaba TX that is damaged by attempted discharge that has the diode protection. The diode's purpose is to prevent damage due to discharge by disabling the ability to discharge. Hooking up a discharger won't hurt anything, but it also won't work because current flow in the discharge direction is not allowed by the diode. As long as the diode is in place, nothing can be damaged by attempted discharge. However, you can melt down the radio if the user attempts a high charge rate, and the diode won't prevent that action. I believe the customer was misinformed when he returned the charger.

It is true that older generation technology (like a decade ago) nicads had some "memory" issues, but modem quality nicads (like sanyos) really don't suffer from memory issues. The only common reason to discharge nicads is to test pack capacity, which only needs to be done occasionally. I only test my packs about 2 times a year. I had one pack that I accidentally discharged thru the RX for a week or more. The pack was very dead, but even after that abuse, the pack still read an open voltage as Rodney posted. After recharging, the pack tested out just fine.

Cheers.

I used to worry about this, & maybe years ago batteries were not as good as now, but for a long time I have mistreated my batteries according the guys who still worry about it. I fly them as much as needed, or as little as needed & don't worry about the state of discharge -- I just make sure that they are fully charged before flying. I have not had problems & my batts last as long as theirs.

In the fall I commit a major sin according to the battery boys -- I charge them fully, then ignore them until spring, or when there is some winter flying to do. I cycle them in the spring & away they go -- just like the ones from my anal battery buddies.

Come & get me fellas --[sm=punching.gif][sm=biggrin.gif]

Go on over to the radio support forums for Futaba and do a search for the word diode. There are 3 radios so far the has this "protection" built in so that you cannot cycle the battery in the radio

Here is a link to one

http://www.rcuniverse.com/forum/fb.asp?m=1575824

I'm wrong to cycle and Nicad cells are now incapable of developing memory? Fine for you; but, I think I'll continue doing what I've done and been successful with.

My understanding of the diode, also, is to keep the pack from being able to discharge. I have to remove my pack to cycle, also (Airtronics).

I cycle when I want to know my battery pack is working the way it's supposed to. I also monitor voltage at the flying field. O.K., now you know, I'm anal, wrong and I don't believe some of what you guys have to say!

Okay - so if I understand the gist of the postings here - I am doing minimal harm by simply charging both RX and TX stock batteries overnight before flying. Monitor the batteries dischage rate during use, and make sure its not excessive. Purchase a recycler, and cycle them once in a while, dont just leave them on until drained.

Now what about the 12v gel cell field battery?

I fully agree with the above, Yesterday at our club meeting, we had a battery clinic , when I thought I knew something about nicads, guess??? What?? The club members giving the clinic were very qualified. some of them made there own battery analyzers.

Found out I just knew a bit after the clinic. I could repeat some of the thing that we learned, but I won't! after reading (some battery questions) thread, I'm not getting involved in this discussion , I also recommend going to http://www.rcbatteryclinic.com/ you will find the answer to your questions and decide for yourself what to do and not do.

roltech

i have the accu cycle not elite works great gives the time in minutes it takes to discharge the pack at the set discharge rate u et it to i think there are 2 or 3 diff discharge rates

I have two of those Accu cycler's, I have lots of batteries so time is a factor when they need charging and want to check the packs about twice a year. I only use nicads so I don't need anything else.

roltech

Care and Feeding of your Sealed Lead Acid Battery ( Artical taken from RC Batteries Clinic)

(aka - gel cells)
Lead Acid (Gel Cell) charging

Lead acid (gel cells) should be charged with a constant potential charger specifically designed for these batteries. These are sometimes referred to as a CVC charger. You can charge them with a constant current charger but you must terminate charge when the voltage reaches 14.7 volts. You should not exceed the C/10 charge rate. If you have a 7 Ah battery in your field box the maximum constant current charge rate should not exceed 700 mA. It will take about 14 hours to charge from a fully discharged state (voltage less than 12 volts).

A CVC (Constant Voltage Charger) is exactly what the name implies. It is clamped at a certain voltage and puts out all the current it can until the battery reaches the clamp voltage, usually something around 14.5 volts, then the current drops off to maintain it at this voltage. A constant voltage charger is characterized as one having a current capability of supplying a fixed voltage to whatever load is applied. A constant current charge on the other hand will provide whatever voltage is necessary to force a fixed
value of current though a load. Constant current charges have a much higher internal resistance than the load so that any variation on the load will not change the current being supplied. Constant voltage charges have a very low resistance as compared to the load and will supply whatever current necessary to maintain a given voltage at the load.

Many inexpensive chargers used for sealed lead batteries are what is called taper chargers, these are set up so the voltage tapers off as the full charge voltage is reached. True constant potential (CVC) chargers can be quite expensive so a compromise is made in the design to control costs.

We have used the term sealed lead battery in this discussion. These batteries are not truly sealed as cylindrical Ni-Cds are. They have a gelled electrolyte system where there is a modest recombination of the oxygen in overcharge in some designs. All require venting of the oxygen and hydrogen byproducts of charging and discharging. This is why you should never totally seal these in a field box where these gasses can accumulate. Mixtures of oxygen and hydrogen can cause spectacular "events" if a spark is provided (from an electric fuel pump motor).


How much charge is there in the battery?
Unlike Ni-Cds you can read the remaining capacity quite easily with a voltmeter.

After the battery has been on rest for a few hours read the voltage (no load). 12.0 volts is essentially fully discharged while 13.0 is fully charged. This is a fairly linear relationship so a reading of 12.4 volts means you have 40% of the capacity remaining.

Never leave a lead acid battery in the discharged condition.
The lead acid battery should never be left to set in the discharged condition or sulfation will result. The sulfuric acid in the electrolyte reacts with the sponge lead active material and forms lead sulfate. It is a poor conductor. This coupled with the H2O left after you take all the S out of H2SO4 is also a poor conductor so trying to charge requires a lot of voltage to push the current through required to convert the active material back to the charged state. Sometimes they just cannot be brought back from the sulfated state.

The good news is that sealed lead batteries retain their charge much longer than Ni-Cd, At room temperature it's well over a year. So all you have to do is make an occasional open circuit voltage check to see if you need to charge it.

roltech

Kerberos32, Piper mentioned the battery clinic website. I have read most of the stuff there and even emailed and got a reply from the owner. There is much good information there, don't pass this stuff up. The owner feels battery memory is no longer and issue, so according to him, we don't need to worry about this, which is good news. I still think occasional cycling of your batteries is a good idea!

Ditto on that Mode One.

That is exactly what we were taught last week at a batteries clinic at our club meeting.

roltech