Ansmann Max-E cells are probably even better than Eneloops (I've been working with them professionally), if you can find them with tags. The only thing I'd say about Low Self-Discharge (LSD) NiMH cells is that they don't like high currents. However, R/C duty cycles probably won't trouble them unduly.

i think what Mr. Cox is trying to say is that the redundancy system is making something that he already has trouble with even more difficult............and it is, but only if you aren't one to stay on top of things and have a good routine checklist on paper and in your head.

certainly no one has to use a redundancy system, but for those of us who have seen switch failures or a failed cell bring a model down, then the system becomes commen sense.

LOL, that is classic, along with the one who isn't willing to advance to the next level eh?

Just so everybody nows what I am trying to acomplish, the reason I started this thread is because I wanted to see what others out there are thinking, and doing. I do have my own ideas, which I am now juggling around due to some of the posts in this thread. This thread is helping me decide which way to go. For example, I have been trouble shooting electrical and electronic equiptment for a solid thirty years. I never liked the idea of switches due to the fact that I have replaced dozens of them in many aplications. I was going to go with 13 dollar switches until one of you guys mentioned vibration. Now I am thinking, good quality or not, is it worth chancing. Maybe I'll go with a Deans plug for a switch. More of a pain to plug and unplug but it seems to be more reliable. Point being, I might know, or think I know quite a bit, but there is often something overlooked.
Some of the replies have sort of mentioned, for a 40 size plane, there is no need to go to any extent. I don't get that. The way I see it, my Toledo Special cost $225.00. Saito 72 - $225.00. Spectrum AR 6200 - receiver - $99.00 and misc. bring the plane to a grand total of $600.00. Why not spend another 50 or 100 at this piont to cut down chances. Guys at the feild I fly at talk of bad switches, connections, and batteries too often in 40 size planes. I am not trying to make the plane bullet proof. Just trying to change the odds a little. How would I feel at this point if I lost the plane to a bad switch, battery, or connection if I do not spend the $50.00 for a back up. To me it makes sense to go with two quality Nimh without regulators, and check voltages and current draw before and after each flight. Maybe no switches. I'll tell ya, that was a good point made about switches and vibration.
More than the money that will be lost over a bad connection is the agravation building the plane due to poor instructions, and some shakey material.
I know you can only go so far, but it is deffinetly worth the money from what I hear, to double up the power source with minimal added connections.

Thanks again for all the input.
Mike

There is an old German hunting saying:

All skill is in vain if an angel pees down the touch-hole of your musket.

In other words: many things are outside of your control.

It is not truly a bad thing to build redundancy in a system: provided you don't over-complicate it and ADD failure points. Remember Occam's Razor. In a .40 size model the added weigh of a second battery pack may increase the wing loading to the point that it flies poorly and/or lands overly fast . . . increasing the risk of a calamity. I've got a 15-1/2 pound Giant Super Sportster that I fly with a single switch and battery. It is much easier to remember to charge one battery and keep abreast of it's condition and discharge characteristics. I check it before and during the time at the field (between flights) and have a VoltWatch 2 wired onto the model's dash so I can eyeball it just before I taxi out. But I've also got a pretty sophisticated redundancy set-up in my 27% Ultimate (THREE heavy-duty switches: two flight packs and an isolated ignition pack).

I haven't decided which is the better system. Neither has shown any signs of failure . . . yet.

This also makes me think of the odds of failure and how they don't stack up the same. I have seen planes fail with more redundancy just as much as those without. Just think how some can fly for 30 years and rarely, if ever, have a failure and one does all this redundancy and his system fails. Granted redundancy can be good but at what level is it really needed and how much should be implimented?

The more complexity you add, the more levels of risks you might be adding. That is why someone can fly 30 years without a failure because they do not introduce additional points that might create even more risks, but use good components and keep proper check on them. As you stated, "...charge one battery and keep abreast of its condition and discharge characteristics."

My philosophy is buy decent components from good manufacturers and do proper checks. You could also put this in the term, pay close attention to sound and any abnormal behaviour that could be a possible failure waiting for a place to happen. Think about it. Any one mechanical failure can bring your plane down.

Say you take all the redundancy you can build into the electrical system, but fail to pay close attention to your elevator servo and one day you hear a sound while flying, "SHPLICK...GGRRUNNK" and your plane comes tumbling down (add sound effects as needed here

The best path is to pay close attention to any changes in your planes characteristics. Are there different sounds, change in vibration to the airframe, servo acting strange, was that a flutter you heard, landing gear secure, engine firewall solid, engine smooth as normal, servos solid in their mounts, all screws tight, etc.? A watchful eye and ear will keep you flying longer with much less failure and will minimize risks.

That is my .075 cents [X(]

LOL, yes that is indeed the main cause of failures. It often masquerades as "interference"
Well at least at my airfield.

I will reinforce the point I made earlier, the humble switch is the most overlooked component in the entire planes power system.
We spend hours trolling the net and LHS's to find the right servo for each control element, we are eligious in our brand devotion to TX / Rx manufacturer, we even go so far as to re glue an ARF that for all intents and purposes wil remain glued no matter howunskilled we believe the hands that made them are..... but we spend bottom dollar and 30sec in LHSwhen selecting the humble switch and even less time installing it.
I have seen planes with a toggle switch on the top of the wing. The toggle swithc had a light spring and the Off direction was toward the tail....

In the interest of full disclosure, I recently had an experience where the "watchful eye" saved my big investment (30% PRC Yak 54). I noticed as part of my preflight checks that the spinner appeared to be vibrating excessively. Further inspection revealed a cracked firewall support. Had I flown the plane, chances are the firewall would have come apart completely and I'd have lost the plane.

The only redundant system I installed was the switch. I have a single battery that goes to two switches, and both provide power to the same reciever. I subscribed to the notion that the switch is the weak link in the chain. With two switches, its easier to identify a failing switch, and by checking each switch on startup, I improve my odds of finding it before disaster. Batteries are A123 that I keep track of the capacity. Voltage feeds back to the transmitter real time, and I know my "no-fly" voltage.

The trick is knowing what behavior your plane exhibits, and when its different, finding out why. Does the radio glitch if the switch is jiggled? This is usually the first indicator of a worn or failing switch. Do servos glitch when wires are shaken or tapped? Is the plane vibrating more than it used to? Does it sound the same?

Brad

Ihave actually tested the possibility of having a dead battery drain the good one. Idischarged a battery and connected it in parallel with a good one and let it sit overnight. The low battery did not get charged at all and the good battery did not get discharged. The good battery just isn't capable of charging a dead one. Even using them to power a receiver and servos showed no issues.

Shorted cells might be a different story of course.

Forgetting to turn on one switch could be a problem too but you'd likely get a good flight out of the one that was on. the next flight you would turn them both on and it would probably be no big deal.

Like I said before, I might not run a redundant system in a 40 size airplane where weight and space were a concern. I would just use quality components and keep track of the battery condition. When it comes to larger airplanes though, I like the added security. It isn't foolproof but it can make a difference.

IMHO simplicity is good. Since many years I use to power my onboard radio system with one unregulated 5-cell NiMH battery connected to the Rx trough an electronic switch that has no mechanical parts.
The most common failure mode for NimH batteries is internal short circuit. The probability of this happening to more than one cell in a battery pack at the same time is as close to zero to be neglible. If one cell fails through internal short circuit four cells remain to deliver 4.8 V which is enough voltage to power any R/C radio system.

Here is link to the electronic switch I use:

[link=http://shop.rc-electronic.com/e-vendo.php?shop=shop&SessionId=&a=article&ProdNr=A1 7000&t=6&c=26&p=26]EMCOTEC DPS Switch[/link]

Great catch! Just last week I had a similar situation and I even noticed something the week before. I kept hearing a slight variation in engine sound on my Pulse XT. I have flown the plane around 175-200 flights and I heard a small but noticeable pitch/vibration change and I had noticed the week before my switch on the side had two screws loosened. I checked my engine and she was smooth as silk and really could not find anything wrong. Well, I was flying it Sunday and I went to start it and noticed that the engine seemed to move back slightly. After further inspection I saw the firewall was cracked and would move about an 1/8 of an inch.

The point of this is that the sound or change in the characteristics of the plane was giving me an indicator that something had changed. Careful inspection is vital and is the real key to save planes. I do agree that switches are probably the weakest points outside of connectors. You have to make sure your connectors are vibration free and well connected or you will soon find out just how good they are [X(]

Along these lines, I never heard any noticeable sound, but my RTF PTS P-51 mustang had its firewall floating about 1/8" forward under power and when I bent it by hand. I took it to the hobby shop and asked some of the seasoned veterans of the hobby, and they recommended quickly sealing it with epoxy if possible. I did just that, and it no longer moves, however they were very surprised by it (I guess nobody should be surprised considering the discussions on here about the quality of ARF/RTF glue joints.... but they were). I've learned not to trust ARFs, but at my green/newbie level in the hobby, and considering my shortness of room in my college dorm/apartment, I certainly can't build my own planes (my most recent plane was built from a kit by a professional carpenter).