Joystick TX

I had to edit this a lot, I messed up. Chemo brain?


I've been watching the progress of the LiFe batteries for a couple of years now and haven't seen any "single" batteries that have failed in flight due to "opens or shorts", so it looks like they are doing pretty well.

Seems like it is time to replace my NIMH two 5 Cell battery system for a LiFe one battery, 2 Cell, system.

The LiFe 6.6V receiver battery comes with two "universal" receiver connectors. Instead of using a Y connector and single on off switch with one connection to the receiver I'm using two switches and two connectors to the receiver for redundancy.

If one of the LiFe cells opens, since they are in "series" to get the 6.6V, there will be no voltage going to the receiver, so this is not as good as the two battery solution that I used to have. The good news is that the LiFe batteries do not seem to be as susceptible to that failure mode as the old Nicad and NiMh batteries were, so for me it is worth the risk.

I still like the two switch installation. Mostly for redundancy, the switch is the least reliable right now.

The LiFe battery will need to be taken out occasionally to balance the cells, or an extension lead will need to be attached.

See diagram for my installation:

Tom Nied

Please excuse my ignorance. What is the advantage of using a single LiFe battery? I'm currently using a two battery system. 2x NiMH 6V 2000mAh. What seems to work for me (in my mind) is that I like the engine has its battery, and the Rx and servos has its own battery. I've had a 5 flight (15 minutes each) day and all seemed well. Don't get me wrong here, I'm amazed how you simplified your battery needs. I just feel (maybe ignorantly) secure about having two different systems. Obviously you are ahead of me in the battery game. Thanks for sharing. Tom

ahicks

My Feedback: (2)

Very nicely done Steve!
Steve's drawing represents a setup I've been talking about for several years now. It's light, simple, inexpensive, offers twice the amperage capability to the entire flight pack over what a single switch system offers, and complete power redundancy from the battery to the receiver. A bonus for those flying acrobatics requiring heavy use of the rudder, is that the rudder, when wired per drawing, has a direct feed from the battery, without having to go through the receiver.

I also agree with his thoughts regarding the LiFe battery technology. They seem to be doing REALLY well, especially when compared to NiMh.

LiFe batteries are capable of delivering incredible amperage - enough where a single switch becomes a choke point in a high performance system using digital servos. In a plane the size of a Giant Sportster, or really any plane flown hard that's equipped with digital servos (even 20cc stuff!), the servos are often capable of pulling so much power that voltage to the receiver may drop enough where the receiver drops off line - with predictable results (this varies by receiver, some are more prone than others). The double switch/LiFe plan pretty much eliminates that potential. That was my original reason for going with this setup. After going this way, "bonuses" kept popping up as I realized just what it's capable of when wired per the diagram.

As far as the necessity of providing the ign. module with a stand alone battery pack, go for it if it lets you sleep well. Just know MANY are using the same battery the receiver is using - without incident. There have not been ANY reports of problems using that method. -Al

Joystick TX

It is mostly a matter of preference. There are pro's and con's with every setup.

I used two batteries for years. Post #3016 shows the two NiMh batteries and two switches (ignore the charging note). That solution gave true redundancy. If one battery fails open, the plane can fly with no problems. I only used my NiMh batteries for two years before I replaced them, but I put over 500 flights a year on each one of my planes. I never lost a plane that had two NiMh batteries with the way I had them connected.

I never liked a separate battery for the ignition and receiver, that solution did not provide any redundancy. In the "old days" it made sense to have a separate battery when the ignition voltage was different (lower) than the receiver voltage. Now the new ignitions can use the same battery voltage as the receiver. With the separate ignition/receiver battery setup, if the receiver battery failed, there would be total loss of control and the engine could continue to run if the the fail-safe was not set correctly. About half of the ones I've checked at our field were not set right. If the engine battery failed, the second battery would allow control with a dead-stick ASAP. Also, the new ignitions only draw about one-fourth of the power of the old ones, so a high-capacity battery for them is no longer required. A 2100mAh battery would run my ignition for almost 20 hours.

The only problem I have now with two LiFe batteries is cost. I have four airplanes to support. The initial cost is high, also like ahicks mentioned in post #3013, if you forget to turn off your system it may trash your batteries and that could be very expensive. The NiMh batteries could recover, with the LiFe batteries that is not guaranteed and I would not trust them if they did appear to recover.

Since the each 6.6V LiFe battery only has two cells and does not seem to be susceptible to the single cell failure like the Nicad and NiMh batteries I'm willing to take the risk and use a single battery now. has two cells which is the equivalent of two separate batteries, I like the redundancy that provides, so I don't need a separate battery.

I don't fear deadsticks with the GSS, I've had hundreds of them and have only peeled off the landing gear a few times. The fuselage mounted gear is great.

Tom Nied

OK, be patient with me, I'm trying to understand this and I'm fascinated with it. Almost got it. But you say " The only problem I have now with two LiFe batteries is cost". Are you using two batteries per plane? I don't think you are.

Joystick TX

Removed.

Tom Nied

OK, thanks. Could be me too. I study the written and compare to the diagram, and just kind of get confused in it. I'll stay tuned. Thanks

Tom Nied

That's pretty slick. I looked at that battery on Tower and it goes for about $35 a piece. Isn't that actually a savings? Weighs less too than two NiMh batteries.

Joystick TX

No problem Tom, thanks to your question, I found a big boo boo in my diagram and had to correct it and some of my posts.

The LiFe batteries cost me more than the NiMh types. If I forget to turn off my plane and fry the LiFe battery, it will cost about $35 instead of $70 with the two battery setup. The cost of forgetting to turn off a plane with the NiMh battery was zero.

I'm in the process of modifying one of my planes tonight to have just one LiFe battery. Hope to have them all done by next week.

Your two NiMh (five cell) battery installation is great except I don't recommend the separate ignition battery due to the loss of redundancy, but that is up to you.

The most common failure mode for the NiMh type of battery is an open cell, and since they are in series, that gives zero volts output. The one battery that I had with a shorted cell killed the ignition, but with a second one in parallel it still gave me enough voltage to power the servos and receiver and get back to the field and land safely.

I've been flying RC planes since 1971 and have had many switch failures and only a handful of battery failures. I fly all year and a lot, so I've had way more failures than most people. I was also an Avionics and Weapons engineer before I retired, so I like redundancy and for things to work well.

I almost forgot. With a single battery, I only have 2100mAh available for flying, which is half of what I used to have with my two battery setup. I also used to fly 8 to 10 flights a day, all about 15 minutes each. Now I only fly four or five flights with 10 minute flight times, so that gives me enough of a safety margin to feel good with only one battery.

Joystick TX

It is not a "savings" if you have a LiFe battery and you forget to turn off your receiver and trash the battery. If you have two LiFe batteries you may even cry.

Fortunately, I don't do that very often. I'm more likely to forget my wing, or transmitter when I go to the field.

As far as the weight difference, with the GSS, you probably won't notice any performance difference.

ahicks

My Feedback: (2)

Might be worth pointing out as well, is the fact that as airplane size and power are increased, the weight and size advantages of a single battery system decrease considerably for most of us. In that case, this same wiring diagram (post 3026 above) can be used equally as well by substituting 2 batteries feeding the 2 switches, rather than the one as shown.

As far as battery removal to balance charge, nope. There's a way around that too. It requires that you modify the battery slightly. Using the standard J type connectors, you can use the white/3rd wire as your balance wire. This mod in place, you can make an adapter for your charger to allow the use of the switch's charge port to balance charge. The one "gotcha" to this plan is the need to cut the white wire on the output side of the switch. The receiver has no use for 3.3 voltage on the signal buss. -Al.

Tom Nied

Whew, I better stick with my two NiMh batteries for awhile. It has some advantages for me.

Joystick TX

Here is a diagram to help with a dual battery setup:

Joystick TX

Are you going to use one battery for the ignition and the other one for the receiver, or are you going to set them up to do both so you have a backup in case one fails?

Tom Nied

I have it setup as two independent systems. One battery for the ignition, the other for the receiver. If I have a deadstick, I've got plenty of practice at that, and I'm not going to worry about that. Losing power to the Rx shouldn't occur, I check that battery every flight. Flawed thinking? My ears are open. I studied your diagram for a two battery system. The most flights I've ever gotten in one day only amounted to 5. I do utilize a DLE Engines Opto Gas Engine Kill Switch (RCEXL)

Joystick TX

Your system will work okay. You just don't have any backup for the RX system when something does fail. The flights per day does not enter into it, unless the number of flights is zero.

Since you already have two batteries, your system can easily be changed to give you almost double the reliability, with very little effort and only a couple of dollars for a Y connector.

Don't confuse "reliability" with "life expectancy." When you say "Losing power to the Rx shouldn't occur"; I agree, but stuff fails. The two highest times for failures are when things are new and when things are old. A dual system takes care of those two times.

I quit using the Opto Kill Switch a few years ago due to failures. I see about five failures a year at our club. The good part is they hardly ever fail in flight. They just cause a lot of heartburn when trying to restart the engine since they are the last thing people check.

Tom Nied

Yeah, I get it now. Now I see how the Y connector makes the difference. Will consider that. And yes, I've already done the failed restart when another flyer distracted me from my starting checklist and the kill switch on the Tx was thrown to "kill" from the previous flight engine shutdown. Thanks for the enlightenment. I will have to keep a keen eye on this part of the system.

silverwings

My Feedback: (21)

I know this thread has been dormant for a while, but I have a question. When installing Robart hinge points, do I need to install more than the CA hinges it had originally? I purchased the plane at a swap meet and need to do the hinge upgrade.
It already has the tail bracing and langing gear moved to the fuselage. I will also be constructing carbon fiber linkages for all flying surfaces.

Joystick TX

I'm not exactly sure what you're asking. I think you are removing the CA hinges and replacing them with Robart hinges.

If you are replacing the CA hinges with Robart hinges then you can replace them on a one-for-one basis. If you feel that more are required, you can add more. It's a good idea to have not less than three hinges per moveable surface.

On gas powered planes I like to use four hinges on the short surfaces like the rudder and elevator halves and 5 on the ailerons.

The Robart hinges can also fail or come loose after enough flights. I have run three engines to destruction on my GSS, I'm now on engine number 4, and have had to replace a few Robart hinges.

silverwings

My Feedback: (21)

Thanks, Joystick, that is what I was asking. Sorry for the confusion. Also, thanks for the information about the robart hinges also failing. I probably will not fly mine as hard as you fly yours so they should last me a lifetime.
Rick

silverwings

My Feedback: (21)

Glad to see someone is still monitoring this thread. It has a lot of great information in it.
Rick

Joystick TX

It does, unfortunately it is hard to find the wheat from the chaff.

The control surfaces are subjected to a lot of forces that we don't think about all that much.

I used the stock control rods, etc. when I first built mine and beefed them up a lot after reading some posts on this thread.

Here is a great video of what vibration is doing to the control rods on the ailerons.

If you look close, near the end of the video, you will see the horizontal stab leading edge moving up and down at the tip. That twisting can be bad news too. That's a good reason to brace the tail feathers even though it is not a requirement in the instructions.


If the video does not play you may need to copy the link and paste it into your browser.

Tom Nied

Joystick TX, you have run three engines to destruction? How does one do that? I don't think I've ever run an engine to destruction. I'm not doubting you, but just curious.

As far as the hinges I agree with Joystick TX. In fact I wish I had used the Robart. I used the DuBro heavy duty with the brass cotter pin and I've had to replace a couple already. The good thing about the DuBro heavy duty hinges is that you can pull the brass pin and get to the broken ones easily.

Another area of concern is the tail wheel assembly. I didn't use the stock version that was supplied but used the Sullivan for that weight class (14 lbs.). It only lasted until the first marginal landing. It got bent out of whack and I never could get it straightened out. So I've swapped it out for a carbon fiber type used on gas arfs. I'm in the middle of the flying season and threw a curve ball at myself by buying a new transmitter. So now I have to reset all of the throws and check that all out.

I've really got finish my fixes and mods and get her back up. It's really a "Great Plane" to fly.

Joystick TX

I was doing engine testing for a UAV project. I was testing different oil types. I ran through 2 to 3 gallons of fuel every week all year long on a 30cc sized engine. Usually the engine bearings would get rough, or the connecting rod would get some slop in it and rather do preventative maintenance like most users, I ran the engine until it failed. Usually the rear bearing race would come apart and FOD the engine. We were trying to get 500 flying hours, none of the engines I tested made it, the most I had was around 250 hours.

The tail wheel that comes with the kit won't hold up long on grass runways if you like to do touch and goes. I think I'm on my fifth or sixth tailwheel assembly.

I only fly 50 to 100 hours a year now, old age and cancer slowed me down a lot so my planes are holding up much better.

Tom Nied

OK Steve that pretty much explains all. Hope you're feeling fine. I don't get nearly any kind of time like that on an engine. What you describe is pretty intense. But from what you tested, what did you learn? Can you disclose what you did learn from your testing? Like what are the things that help an engine prolong its life? I'm running a DLE 35ra on my GP GSS and if I get 4 flights an outing, I'm doing pretty good. Thanks for sharing.

Tom Nied, Carol Stream, Illinois