I am looking to power the radio in a just built Toledo Special. After hours of research, giving me a good size headach, I came up with using 2-two cell Lipo,s, with a Smart Fly Sport Regulator. The outputs will be plugged into a Spectrum AR6200 receiver.
Can anyone chime in and let me know your thoughts?
Thanks.

Mike

I had to check the - Notify me via e-mail when someone replies - in this reply.

You don't need to post again, just click the "Subscribe" link (now that you are subscribed, it says "Remove Subscription" )

I forgot to paste the link to the Smart Fly Regulator in my first post.<a href="http://www.airwildpilotshop.com/MoreInfo-1.asp?title=product&amp;id=843">


http://www.airwildpilotshop.com/MoreInfo-1.asp?title=product&amp;id=843</a></p>

That's a 40-sized, old-school, plane right? Two batteries plus a $60 regulator sounds way over the top to me....
What's wrong with one good NiMh battery and a voltwatch?

G'day I agree with Mr Cox, a 5 cell pack of Eneloop or similar high quality NiMh cells is more than enough. AND it is simpler and so less likely to cause problems. LiPos are wonderful where you need very light weight for power but they are fragile in crashes and can be easily destroyed by incorrect charging. Simplicity for me.

The most reliable configuration you can achieve is to just leave the wing off and leave it in storage.

Seriously though, if this is a typical 40 size trainer, there's no reason to spend a lot of time and effort adding weight with extra batteries and regulators. Modern radios are reliable when properly installed (padded), and nearly all the choices for batteries are reliable. The dual battery setups, regulators, etc. are for the guys spending megabucks (read thousands) on large scale models where vibration may be significantly higher, and there's far more at risk.

If you install all the equipment properly, clip or tie connections together that you don't undo after a day of flying, follow good pre-flight procedures, there's no reason, other than pilot error, that your plane shouldn't last a very long time.

Brad

Even with the most sophisticated aircraft that I own, I have a basic radio battery setup, exactly as described by Mr Cox. Keep it simple. This removes any additional points of failure. If you are concerned about voltage, get 5 cell NiMh or NiCd and a voltwatch and go with that.

Hello again. I currently have about 30 planes of various sorts and over the last 10 years or so I have probably had another 30 or so. To date, I have only had one failure that was traceable to a battery failure and that was simply that I had not checked it for some time and a battery connection was loose and let go in flight.

I have never had a battery fail in flight. To make sure this does not happen I have voltage sensors in all the planes I fly regularly and I keep an eye on them. Planes that I fly less regularly get their battery cycled a couple of days before I fly and I write the capacity on the battery on in the place so I can compare it next time.

Lately I have been using Sanyo Eneloop NiMh batteries when I can get them. They have a very low loss rate in storage and do not loose charge over many weeks though I usually top them up before use and cycle them every couple of months. They really are worth the little extra they cost.

The other problem these days is the huge numbers of cables and connectors coming out of China. Some are fine but many do not fit properly and are either too tight or too loose. Worse, hobby shops are tending to stock the cheap imitation cables and switches because they are cheap and it is becoming harder to get real JR or Futaba or Hitec cables and switches. I am sure this is going to cost people some models.

Thanks to all of you. Simple is the way I wanted to with originally, untill someone told me stories of false peak readings on Nimh batteries causeing planes to go down. Maybe they purchased the batteries and charger from Radio Shack. I beleive that I am now convinced on keeping it simple. I have worked in electrial and electronics for 30 years and realize that the less used, the better.
Thanks for all advice once again.

If you really, really want the redundancy, you can use two separate receiver batteries and two switches. Just plug the second battery into any un-used receiver port or connect it to an occupied port using a Y-harness. Doing this with two NiCads or two NimH is a lot cheaper than all the lipos and regulators. Also, I may get some disagreement on this, but I have seen lipos fail and I have seen regulators fail far more often than I have seen problems with NiCad/NimH batteries or quality switches.

The second battery will add some weight though so I generally only do it in larger airplanes where it isn't as much of an issue. For smaller airplane like a .40 size, I usually just run one good 5-cell battery, generally 1500-2000mAh.<br type="_moz" />

redundancy explained.
a well respected member of our club and i have gone over this system for quite some time now.
charge each battery seperatly or disconnect one if charging both at the same time as the system uses a shared ground that some chargers except wall warts don't agree on.
haven't seen anyone use lipos or regulators tho.

Summerwind's picture says it all, by far the most reliable and simple way to solve the redundancy problem. I also suggest the use of Eneloop cells for the ultimate reliability. Much cheaper than LiPo's yet chargeable with the most simple of chargers including the wall warts that come with most RC transmitter/receiver combos.

+2 for summewind's suggestion.

Switches don't weigh much and if you use the AAA size NiMH packs you will have less problems than with the AA size packs.

I use two 750mA.hr4.8V packs but through one switch in my trainer.

Current planes have LiFePO4 packs in them but only one through one switch. Thus far them seem reliable

I'll third that suggestion. I have two pattern planes with exactly that installation, using a pair of 1200 mah NiMh packs and a voltwatch. This configuration saved a plane when one of the battery packs went bad during a flight. The other pack was there and I never noticed a difference at all. Once I landed, I did the usual battery check and found one of the two to be dead, or near dead. I replaced it with a spare that I had with me, put both on the charger to get them both peaked and then went back in the air.

CGr.

Thanks again guys. This is helpful to hear multiple suggestions. The only thing that I think about is if one of two packs short out causing the other pack to go low in voltage. I have not put much thought into the possibility but with little thought, the chances of a shorted battery pack would prob. be limited to one cell of the pack. If that were the case, I beleive the higher voltage of the good pack would stay constant. I also beleive that I think too much.
This is what 11 years off of the Budweiser can do.
I am going to check into Eneloop batteries.
Thanks.

Mike

It would have to be a pretty serious short to cause any problems I think. Nothing is 100% fail safe. There is always some remote disaster scenario with any system. The receiver could fail, the tail could fly off, a multitude of things could go wrong. The 2 reliable batteries and 2 switches in parallel has far less chance of failure than lipos, regulators, and stuff like that in my opinion though.

I'd never use a Lipo for a receiver pack. The fact that they have to be run through a regulator puts me off since these things tend to fail quite frequently if I cast my eyes around toward fellow flyers tool boxes...

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I don't understand the purpose of the two batteries and two switches...

The only thing I can think of is that if one switch would suddenly fail in flight (I don't know how), then you would fly on one battery rather than none, so that's a good thing.

For all other events it appears to not do much at all. Forget to charge a battery and you drain the healthy one. One battery shortcuts in the air, and you drain the healthy battery. Forget one switch and you have half the flight-time etc, etc.

I'm still all for one good NiMh battery, one good switch (protected from glow fuel) and a voltwatch that is visible from the outside of the plane.

Another good thing about using two batteries in parallel is that the equivalent internal impedance is cut in half, very beneficial for systems which draw gulps of high current (thing several digital servos in violent maneuvers) as there is less chance of getting a voltage depression on the receiver bus and causing a reboot on 2.4GHz systems. Another plus, it is often easier to find a place to mount two smaller packs than one large pack. Since switch failures are probably the most probable cause of in flight failure, the two switches also add to reliability. Note that most switch failures are where they start to have significant voltage drop due to contact contamination rather than a catastrophic open. That type of failure is very hard to analyze or even find when you are having intermittent drop outs or reboots.

Yes, compared to a single battery of the same size. But putting two smaller batteries in parallel, compared to one larger battery, I don't see any gain.
A voltage drop over the switch, or the impedance issue, would both show up on the voltwatch as it shows the voltage reaching the RX when it is in use.

For a beginner with a 40 size trainer I still think that one good battery and a voltwatch is hard to beat, considering the simplicity and room for human error.

From all I have read and from experience, the switch fails more often than any other part of the radio system. That is why having redunant switches and batteries is a good idea.

Bruce

switches will fail more often because it th one item in the power system where the builder spends the least amount of brain power. I have never, other than on my own planes seen a switch mounted  with silicone rtv between it and the fuselage. These little items are seldom vibration isolated. yet, the batteries, fuel tank, reciever, servo's everything inside the aircraft is vibration isolated...........not the swtich.

isolating the switch goes a long way to preventing its failure. HAving two of them I now believe is a good idea with a smaller battery connected to each.

Forge to switch one on? Well maybe once, but twice in a day? then perhaps the user needs to retake their solo test because airplane operations and checklist are part of the test.

I thought loose connectors, reversed aileron servos, failing servos, loose crystals, glitching radios etc were far more common reasons for failures than a poor switch?

I have only had one switch that failed on me, and that was when it hadn't been used for about 25 years. Problem was then intermittent but appeared mainly when switched on, so the preflight revealed that.

If the two batteries are only in order to avoid a switch failure there should also be an indicator for when that happens. In the scheme above, the only indication you get is a reduced flight-time as one battery has to do all the job.

Technically speaking, in order to have a fully redundant system from a reliability standpoint, we should have two completely independent control trains. In other words, two batteries, two switches, two recievers, and they should be from different manufacturers/designs. That is to further reduce the likelihood of a "common mode failure" experience by two identical components in separate trains.

Since we don't have any real probability numbers, or failure rate data for any of our components, we are left with qualitative statements about "the most common source of failure". Some believe LiPo batteries are the most likely failure. Others think switches. Still others think servo connections. Bottom line is that for the basic trainer setup, there are enough of them flying with just a standard setup (one battery, one switch, one reciever) to demonstrate they are reliable, and good preflight checks will reveal nearly any failure in the system (regular voltage checks, known battery discharge curve, range checks, routine assembly procedure, inspection).

The most common failue IMHO is the loose nut holding onto the transmitter.

Brad