rctech2k7

My Feedback: (1)

I don't think this is serious opinion but anyway let me explain briefly connecting batteries in parallel are safe as long as correct polarity, same # of cell and same battery type for the purpose of reducing battery resistance, increase capacity, increase power and now redundancy...

BarracudaHockey

My Feedback: (11)

While I don't sell rc batteries for a living, I do consider myself well informed about electronics in general and avionics and rc related stuff in specific, and I don't have a problem with two switches, two batteries, two reciever inputs, on my own personal giant scale planes.

Take that for whatever its worth.

rctech2k7

My Feedback: (1)

In the case of different capacity, the smaller battery must capable of handling the load current based on discharge rating and the amount of energy for the duration of flights. Batteries with larger capacity has lower internal resistance and therefore can carry large amount of current and has lesser power and heat dissipation than the smaller one. The smaller the resistance the tendency to hold end voltage at peak current. With that condition, battery with the bigger size will share the bigger amount of power to the load. However high current demand is not an issue anymore on our flight control system since latest batteries has higher discharge rate but instead the remaining energy left in the smaller battery in case the bigger battery failed. In order to serve the purpose of redundancy, identical batteries is recommended to have the same power supply if either one fails and that is capable of completing the entire flying time of a single battery.

Airplanes400

My Feedback: (349)

There is nothing wrong with redundancy.
There is nothing wrong with redundancy.
There is nothing wrong with redundancy.
There is nothing wrong with redundancy.
There is nothing wrong with redundancy.
There is nothing wrong with redundancy.
There is nothing wrong with redundancy.
There is nothing wrong with redundancy.
There is nothing wrong with redundancy.
There is nothing wrong with redundancy.
There is nothing wrong with redundancy.
There is nothing wrong with redundancy.
There is nothing wrong with redundancy.
There is nothing wrong with redundancy.

Except that sometimes it gets boring!

rctech2k7

My Feedback: (1)

As a matter of fact I've seen a lot good post on these thread, there are plenty of ways on doing these to avoid power failure on our flight control system, although we can still maximize its advantage but the most important thing is the correct circuit and rating. I found our Rx power bus has thicker soldered lead to provide higher ampacity and lesser resistance but I still practice to leave one to the battery port and others in between the load slightly farther from original port. Although it may not matter due to my servo normal requirements but connecting one or more power and load to any port contributes power network to my tiny grid. I also use redundancy on my main battery cable each can provide 5A. I used regulator that maintains 6.0V all the time and monitor battery and Rx voltage using 2-channel display as you can see on the photo. The backup power is standby and can take over whenever voltage at Rx drops to 5.7V.



Direct connection of 2 identical A123 battery to the Rx using deans connector is the simplest I can see but using HD power switch makes it more convenient. While providing regulator controlled by fail-safe switch has another advantage of technology since most of the regulator of today are not just regulator but provides redundancy.

gunradd

My Feedback: (9)

I like to run 2 switches and 2 batteries for the simple fact of an ops check of each switch and each battery before every flight.

I always turn number 1 battery on and test out all controls then go to both batteries and then I go to the number 2 battery and test all controls agian by itself. This ensures both switches and both batteries will carry the load by themselves if one side fails. While yes I can do the same with plugs it would be a pain to plug them in and unplug them back and fourth to check the systems out.

erbroens

Sorry Dave, I couldn´t resist:

https://www.youtube.com/watch?v=x56O4G8VsiA

OliverJacob

My Feedback: (12)

Using 2 batteries without a switch has the advantage of improving the capacity, you can simply add the capacities of both.
In case of a bad switch or plug connection or broken wire between one of the batteries and the rx, the other battery would safe the model.
If a cell shortens out (which odes happen) then the good battery gets drained and will not be able to safe your model.

So if I install a second rx battery, I will also install an electronic switch to separate both circuits. Inexpensive and lightweight.

Xairflyer

My Feedback: (1)

I find that hard to believe, I have seen loads of model crashes in 30yrs and pilot error, engine failure and bad installation are easily the majority of the reasons, if it was due to battery it was simply because the model was flown for another flight instead of charging up the battery, that is again is pilot error, not a fault of the battery, and if a direct battery related problem, it was because it was badly secured or no means use of connector locking, than the battery itself failing.


Yes on my twin battery setups I know the risk is less but to me batteries are consumables and makes economic sense to change them out. More for the case of batteries capacity as I would rather carry on having 5 flights per charge, than drop it to three because I know my batteries are getting old.
Using two battery setups is not really about the battery for me it is the connection of the battery to the receiver I am backing up. I would be more worried about a switch/connection failure than a battery. Lots of times the Battery may be 2ft away, so along with your switch you now also have another connection with a extension lead.

Airplanes400

My Feedback: (349)

Cons for installing redundant receiver batteries ?
Cons for installing redundant receiver batteries ???

Is this a movement starting within the Department of Corrections to rehabilitate inmates and give them jobs installing receiver batteries?

If it its, then I say, "No thanks."
I'd rather do it myself than send my plane to an inmate.

BaldEagel

I'm with Xairflyer on this, in the years (and there are a lot of them) I have been flying, I have never had a switch fail, a battery short out a cell, or any other kind of battery related problem in the air, what I have done is dumb thumbed plenty of airframes into the ground and I have seen others do the same thing and blame something other than themselves.

Preventive maintenance will find most of the sort of issues we are talking about if we know what to look for or take notice of what is happening when we operate our systems, if the switch does not connect properly the first time you switch on, do you investigate or just switch off and back on again and if it now works it must be OK to fly, so many times have I seen that happen, has your radio lost its bind, that's OK just re-bind and fly, these are the two most common problems I have seen that should be investigated to a conclusion, but in most case's are not, nothing may happen on the first couple of flights, but eventually...............................

Mike

G4guy

My Feedback: (13)

I'm sure other full scale flyers can chime in also. I have been flying the Gulfstream series of aircraft for 25 years without a battery failure of any kind, yet we have 2 main aircraft batteries and 3 emergency batteries for systems deemed necessary to continue for up to 60 minutes if required. Redundancy? I wouldn't leave home without it!

I have been flying my turbine jets for 12 years with 2 batteries(5 cell NICAD, NIMH) and 2 two switches directly into the receiver with no Regulators. I am switching to LIFE's now for the ease of charging. I never had a failure and the piece of mind for me is priceless....

Ron

mr_matt

My Feedback: (10)

There was an instant expert that posted on here for years, he was always the contrarion even on the most obvious questions.

His logic was something like "since we can't make_everything_redundant there is no benefit to redundant batteries".

My progression was the same as yours Ron, NiCad, NiMH and going to LiFe. I sometimes run a simple dropping diode or 2 to get the voltage down a bit (depending on servos I am using)but I have gone away from regulators.

rctech2k7

My Feedback: (1)

If the first time I turn it on and didn't work, I know the contact inside the switch is not working properly, could be the spring, dirty contact or it slip. When I turn it off and turn back on and work for the second and more, without back-up or redundancy I will hesitate to fly but still better to abort the flight and replace the switch.

I agree that regular maintenance prevents a lot of problem before it happen but having it will not replace a backup option and vise versa, aka "preventive is better than cure". It's been a practice on large scale battery bank that provides backup power. Similar to our system, it uses series and parallel combination. Single battery with 12V rating which are connected in series to provide higher voltage of more than 200V then combine it in parallel into other groups. This setup does not only provide redundancy but increasing capacity. During maintenance before battery gets weak we can find out easily, if not other batteries can still compensate and we can just disconnect one group of series and replace it without down time. In small scale NiCd battery, the least thing happened is shortened it's own cell once it's old and leave for a while without maintenance.

BaldEagel

Even though I have never had a switch or battery fail, I have been using A123's since they first came out, two of them through two switches, the Kodiak switch also read out the Mah used, will have to check when I first dismantled a DeWalt battery to get at the cells.

Mike

rctech2k7

My Feedback: (1)

I used 2S2P Lipo on my jet and now A123 but I still used NiCd, LiFe and LiPo depending on an aircraft.

rctech2k7

My Feedback: (1)

The pilot/owner or the one who did crash investigation is the best person who can explain what went wrong, the fact that he found it on the battery, it can happen because battery characteristic can be misleading sometimes when it passed halfway when it's old. For battery with plenty of capacity left recharging is not necessary after flights but since impedance is increasing, voltage reading can be misleading to the amount left for batteries with sharper discharge curve.

This following reminds me of life without salvation because there are two appointments a human cannot escape so I urge you all my friend to seek as He cares for us... Romans 1:16

To crash with power issue of a single battery is hard if we know we can be avoid it... We have plenty of options and free to decide but I urge to have at least a second battery because this is the blood life of our jet.

Speedy-Gonzales

My Feedback: (202)

The only problem I have ran into with redundant batteries is that if you have 2 Rx packs and they share a common ground you have to watch what you are doing when you charge them or you will fry your dual charger on one port. I am referring to the Hobbico Accu-Cycle Elite and NiMH batteries. You will get an alarm and "high voltage" alert but by then you will be smelling the pungent odor of electrical smoke. [:'(] Otherwise I give a double "Thumbs Up" to dual Rx batts.

Gonzalo38

I would never fly one of my jets with only one battery.... doesnt matter what system you use to connect them. With today's hungry servos I prefer not to take any risks.

In the past I was using the Smart-Fly battery share in my smaller planes, but in all my jets I have double batteries (Fromeco 5200 Lions), double receptor and a powerbox. Most of the time the additional battery works great for plane balancing purposes so why not use it ?

David Gladwin

Ron, you are of course 110% correct, both you and I all other fullscale operators have detailed knowledge of aircraft electrical power systems, clearly many modellers don't. I still don't understand why some jet fliers don't copy the long established practice of fullsize when such engineering concepts can so easily be transferred to model operation with very positive benefits and only very small penalties in terms of weight and cost. Dual batteries are the case in point.


In almost 40 years of operating fullsize jets from small trainers (even they had a standby inverter for A/C instruments) to 4 engine heavy metal (with at least SIX power supplies to critical instruments and radios) I got to know in great detail the electrical systems of these jets. There is one common thread on ALL of these machines whether military or civilian, US or British built, and that is that anything electrically powered which is critical to the safety of the aircraft or success of the mission ALWAYS has at least one backup power supply. What is always considered is not only the statistical likelihood of failure, however remote, but the consequences of failure. In a model jet with only one power supply which has a loss of electrical power in flight that means a crash with potentially disastrous results to people and property. That is totally and absolutely unacceptable when such a failure and possible consequences of that failure can be virtually eliminated by installing a dual power system, I don't get why some guys just don't get that ! Nor do I get the belief of some that if we can't give everything redundancy then we give nothing redundancy !

I have said it many times before and I would state it again to ANY organisation from local club to Chairman of the CAA or FAA that ALL gas turbine powered models MUST have a dual power supply, and this is becoming increasingly pressing as jet models become larger with greater fuel loads and more powerful engines. If we really value our freedom to continue to operate, almost without restriction, these missiles, then we have GOT to do all that we can to ensure the highest reasonably attainable standards of airworthiness and safety and one area we CAN do ourselves a favour is to ensure that all jet models have a highly robust electrical power system, its not rocket science !

No doubt some of the usual keyboard warriors will disagree !

Regards,

David Gladwin.

sidgates

My Feedback: (2)

Well stated David. I would probably go one step further. Dual supplies should be used in all large models. If the model will carry the load why not run dual supplies in all models. I have been flying R/C since 1952 and in my experience the battery, switch, wiring are the most likely failure points.

bobg

Am with you 110 per cent ,David ,cant honestly see how anyone can argue with that .

I always try to remember my model out of control could cause potential damage or even loss of life!!

And if Iwere ever unlucky enough to crash and hurt someone,

I could stand up in front of the judge and say" well at least on my model I took every precaution to build maintain and keep it as safe as possible"

and that would include a dual battery system back up !

gooseF22

re: batteries: Guys we are retreading years of old ground: David hit the most important point.. most of the battery packs are up to the task.. its the wiring/plugs/switches that we need to pay attention to.. Yes one pack will provide enough power, and yes, rarely does a cell fail.. but.... the wiring does fail thus redundancy is important IMHO.. I once had a battery tab come unwelded and become intermittent.. It was caught when I went to charge it.. hmmm... that would have caused a crash for sure.. but with 2 independent circuits, no issue..

re: two badgers vs. one wolverine.. Pick one wolverine because of batt sharing circuitry with "fail on". BUT... make sure it is ordered with redundant output leads.. same with one regulator.. Im so anal, I use 2 regulators too.. like a smartfly or powerbox does...cheap insurance.. each has 2 leads coming out, so if I dont have enough ports, I use Y cords, or you can plug directly into matchbox if used.. You can also power the data port on most receivers..

re: two batts on one bus... it works and it has been done for years.. no popcorn needed. Yes, the batts will bleed down at slightly different rates, so what.. Its worse when you add regs, because the reg with the higher voltage will load, but again, so what.. If you fly and manage so that you would never use up one battery's worth of MAH, then you are fine.. what causes a "load event" is if the impedence in the circuit goes up due to some event..like wiring getting hot..etc..thats where isolation would be nice.. but if you have a short downstream (tail pipe burns thru a rudder wire..for example), a redundant / powerful system might allow you to land if its sized well.. just ask John Roth... his wiring was smoking, burned..broiled, but the aircraft landed.. it had a 9 channel powersafe rx.with 2 batts.. I wish I had a pic.. it was charcobroiled, but still working..

lots of opinions... lots of ways to complicate things, but whatever you use, you have to be comfortable with it, or you can make a mistake and lose the plane.. A friend lost his plane because even though everything was wired correctly, his charger ergonomics allowed him to hit discharge instead of charge.. it beeps and all.. thinking everything's fine.. ..boom.. so its really an exercise in risk reduction, but you need to feel comfortable with what you are doing.. I know guys that still fly Nicads.. thats perfectly ok.. they are fully trusting and comfortable with it.. cycling.. replacement...etc.. but the wiring / circuitry/switches and plugs will always require attention and planning for expensive planes.. I think jets are less demanding on electrical systems than Giant scale, so I learned from the GS guys what works, I figure it works for me..so far so good....

GR7Racer

I have been using dual battery/dual switch setups for the last 15+ years in what is probably the most demanding/harsh R/C environment that I can imagine....Giant Scale Racing.
High Vibration, high heat, high current demands. I started using this setup per the suggestion by Red's Battery Clinic, whose work has been verified and also endorsed by Steve at No BS batteries... both of these guys are the authorities on RC battery systems, period...end of sentence.

I initially started out using dual Nimh packs with dual heavy duty JR charge switches. That worked flawlessly and I can document a couple of airplane saves to this practice. Both were related to wiring or plugs that failed on one pack/switch combo. The remaining pack/switch was able to complete the flight without loss. The problem was discovered before the next flight when only one switch would power up the receiver.

I have since moved on to dual LiFe packs (no regulators) going straight into either a Spektrum or JR powersafe receiver. This is by far the best setup that I have used or seen both for its current handling capability, reliability, redundancy and simplicity.

The dual pack/dual switch and Powersafe RX systems both also offer lower voltage drops under load as well. This is because of the dual paths to the receiver for current, and the splitting of the load between two battery packs. When you combine the LiFe packs and their great current supplying capabilities with the Powersafe RXs that use large gauge wire for their battery source, you have very very very low voltage drops under load.

As for splitting your desired capacity into two packs (two 1100mah packs give you 2200mah capacity), I have done this for weight considerations in our highly competitive racing series with no problems. A single pack (that is charged) will have no problem completing a flight. The issue is discipline in your routine as you need to make sure both batteries are powering your RX the next time you go fly. You also need to be well aware of how much current you need to complete a flight and also know that your batteries have enough charge to complete a flight if one of them were to fail. A prudent approach is to use less than half of the battery capacity before charging again. Two 700mah packs giving you a total capacity of 1400mah may work just fine for a small airplane that only uses 150-200mah per flight. You could fly it safely 3 times and still have some safety margin to complete a flight on one pack. For a larger airplane that uses more current per flight, you would want larger batteries to maintain that safety margin.

KennyMac

KennyMac

gooseF22

David,
Tidbit... The F-16 has 7 sources of electrical power for the fly by wire system.. Thats a complicated redundancy system!! Its Tiered failsmart