RE: Dual RX Battery & Switch
 

You've got it. All your statements are true.

Jim O

RE: Dual RX Battery & Switch
 

This is definitely very interesting guys!

I've heard of other solutions that claim that in an event of failure, the link will remain ok - so no power lost. Here in Italy one can buy a nice electronic switch that has that property: it is nice because all you see in the outside of your plane is a small jumper with a red band, like a "remove before flight" stuff. You remove the jumper by pulling the red band, and the switch is on. When you land, you put the jumper in his plug and the switch is off: nice to see and it seems to work, many top pilots use it.

But the question I have is: how that devices can guarantee that in the event of failure the link will be ok - no power loss? Is there an electronic expert here?

Thanks!

RE: Dual RX Battery & Switch
 

hey stek79 or any one i have a quick question in reguard to stek79 dual bec lipo setup in the first thread.



now im going to be using the same setup but with medusa bec's
Primary:Lipo 2000mah on a 6v reg/switch 3.5amp
Backup :Lipo 780 mah on a 5v reg/switch 3.5amp

the question is if i manage to pull all 3.5 amps out of the 6v reg will the 5v reg pick up the slack. is this because the voltage will drop on the 6v. or will the 6v reg just burn up because its geting to much of a drw??? help me out here plz

SPC Burrows

RE: Dual RX Battery & Switch
 

I wouldn't set it up that way. I fly with a pair of 730 mAh LiPo packs, each with my own design failsafe 5A programmable regulator set to the exact same voltage output. They share the load and the batteries drain down in a balanced way. If either side has a failure, the other side has the capacity to completely handle all the load that can be thrown at it.

Some seem to like the idea of having a "standby" battery instead of an active, redundant supply as I use. Ask yourself this question: How do you know the standby is ready to work if needed? If you use it every flight in an active mode, you can track the voltage drop after each flight and compare it to the other. If you never use it, you don't know what it can be expected to do the next flight.

Here's one real world example of why this can make or break your airplane. I recently bought 4 Thunder Power 730 LiPo packs, 2 per model. I was putting the 2nd set together for my backup Prestige, doing my normal bench testing of components, and saw a complete drop out of voltage from my regulator. New battery and a new regulator I had just built. I suspected my own regulator, just in case I had an assembly error of some type. Quickly did the troubleshooting to find it was the new TP battery with a bad crimp inside its connector, undetectable from outward appearances. It was an intermittent that had to have the wire held at a specific angle to cause it to fail. It happened on the bench test because I moved things around in between tests. Yet, you could static test this all day long and get perfect results, as long as you didn't arrange the wiring harness that specific way. In flight, with things moving from G's and vibration, it would almost certainly have failed. Had this been used as a "standby" that was adjusted to only work if the primary died, I might never know it had a problem waiting to bite me.

RE: Dual RX Battery & Switch
 

i wish i would hve gone that way but i alreaady bought the batterys and bec's i was hoping if i could get an electrical question answerd. for my next bird i think ill set it up your way NJRCFLYER2 but for now i wondering if my setup will work.

SPC Burrows

RE: Dual RX Battery & Switch
 

Assuming the primary 3.5A regulator is current limited at 3.5A, then the output voltage should start to sag as that point is reached and the backup may kick in and help sustain it at the lower of the two voltages. Keep in mind that in the event that this happens, you are driving the primary to its limit and if this is kept up for any length of time, it will get fairly toasty, unless it has a heat sink or some good air circulation around it. I never like to drive components to their limit, hence the approach I took. Your setup will work, but it has the potential to push things with the primary harder than they have to be pushed.

RE: Dual RX Battery & Switch
 

Stek,
You can take what Red says to the bank. No worries if you follow his recommendations.

RE: Dual RX Battery & Switch
 

Hi,

This is what i was looking for ... great setup!

just wondering about some few things ...
*Is the oddino`s regulator the same as Jaccio reg ? ... thinking about the reverse-flow..
* I was thinking about using two switches with two reg , and separate connection to the RX. Does it matter for the RX (jr ) connecting this to a servo-output ?
* Will a 400-500mah Li-po do the job as backup ? ( 2000-2200mah Li-Ion as primary)

The system is for my Integral, time for some new stuff, just for safety !

Thanks in advance
Kjell Olav

RE: Dual RX Battery & Switch
 

Hi all, I am new to the RX Batand regulator usage and am getting a Duralite regilator - 5.1V 7.5 A rated. The question is: Would it be OK AND stable to use a Flightpower Li-Po 2S RX bat for driving the receiver through this regulator?

RE: Dual RX Battery & Switch
 

Absolutely no problem.

I've used 2 batteries and switches for the past year with absolutely no problems at all - identical 4 cell 1100mah packs (nicads). I've also used a 2 cell LiPo 730mah with a regulator and no problems at all. One can't beat the safety of using 2 switches/batteries.

RE: Dual RX Battery & Switch
 

Kjell,

1. Yes, oddino`s regulator the same as Jaccio.
2. In the setup I described I did just as you are contemplating. 2 batteries, 2 regulators (5.4v and 5.8v) one plugged into the battery plug on the RX, the other into a spare servo plug. If you don't have a spare servo plug you can use a splitter.
3. 400-500mah Li-po will be plenty as each flight (glow setup) uses around ~180 to 250 mah depending on vibration and duration. Just check the main battery before each flight.

I've also gone to a Li-po for my primary battery, they are much lighter.

Keith B

RE: Dual RX Battery & Switch
 

Hi,Excellent work!

I have some 5.1 and 5.7v reg already by hand i will use ... good it was the same type then!
The battery-pack in the Integral is placed rear aft for CG reasons, and not so easy to reach .. i guess if i use Li-po, it should be removed when Charging !? ( safety reasons, and access to the balance-plug)
The backup is no problem to use Li-Po, cause i can put it in and accessable position.

Kjell Olav

RE: Dual RX Battery & Switch
 

The two battery, two switch, two regulator approach with two cables into the receiver is probably the safest approach. In pattern planes where weight is so important, I use a single two cell Li-Poly 900mAh pack and a Jaccio Perfect switch harness that serves as a solid state switch and a voltage regulator. I have never had or heard of a sudden catastrophic failure in a Lithium-Ion cell or a failure of a solid state switch in a model airplane and we've been flying them for close to ten years. In my electric powered planes I use about 50 mah per flight so I could use a smaller pack. I have always charged my Lithium packs in the plane.
By the way my wife's name is Jacci O and hence the name.
Meeky, I would be wary of a 3.5 amp BEC. Especially in a glow powered plane with digital servos. You can draw one Amp without any servo movement. I'd like to know how they behave when the current exceeds 3.5 Amps. I've heard the folks flying 2.4gHz receivers having major problems with voltage drop outs with BECs.

Jim Oddino

RE: Dual RX Battery & Switch
 

Things to consider ...When we are putting more receivers and more batteries and more swithes and more servos up in the air we are introducing more possible failures.
In my club there's a few electronic guys flying F5B and 10 cells racing gliders with big folding props in the nose and 100 amps flowing through the esc's and they have long ago designed their own heat sink circuits for the rx and servos. Us mortal F3A guys have adopted the system because it generates the best performance regarding instant supply of electrons without huge drops in voltage known from Nimh cells. For my Integral, which was the first all digital servo ship for me, I started with 4 2500 AA NIMH cells and did some testing on the table and I was surprised to see the voltage could easily go to 4 volts with all 5 digitals connected and operating under a little stress from my hand. Absolutely not good enough.
The circuit is based on the regulator from Micrel, MIC29502WT and it is usually used in harddrives or other constant voltage apparatus and I have put a picture of the setup in my Integral. 2 lipo's 1300 mAh provides plenty mileage for a flying day.

Note the big cooling fin, that is the required size fin whenever the regulator delivers up to 5 amps and 5,1 volts !!!! Without the fin to dissipate heat to, theres a risk the heat will destroy the regulator

RE: Dual RX Battery & Switch
 

Great!

Your regulators have been used ( and still are ) by the Norwegian pattern community (me included) for many years and flights without any problem, rock solid, a component you can trust for sure!

I guess i am too careful about batteries sometimes ... changing them too often .... Actually, my worries is about mechanical failure with them, shaken by the ys-stroker ...

Now, in this Lithium-days, i guess it is possible to use both primary and secondary batteries within the same weight as the "older" setup i`ve been used ...

Ok, i go for Li-po ,both packs then ! It should be possible to make an balance-extension cable , reaching the aft mounted pack ...

Kjell Olav

RE: Dual RX Battery & Switch
 

I had a Nmp pack that lost a cell after the first takeoff on the Friday before the Gardnerville, Nv contest. This pack had 50 or so flights on it. Was fully charged the night before.. Checked with a load before the flight.. I took off, came back across the field and had lockout from the low voltage. Scott Covey checked the voltage in the individual cells and found one at 0.. Cost me a great plane. I will not use Nmp again.. Now I fly with lipo's for my rec pack.. Wish I would have done the duals on that one as it was my "late" brother Jevan's plane..

Now you have heard of a failure..
I still stand by your switch-regulators though Jim.. They are the only ones I run.. Which brings me to the Q of what do you have for 33% planes? Or can I use these same ones..

Thanks,

C

RE: Dual RX Battery & Switch
 

Hello,
nice to see that the discussione went ahead!

I can confirm approximately the figures steted by Keith regarding capacity drained / flight. In my glow pattern plane, with 7 servos:

- 2 jr 8401 (ail)
- 1 standard servo (throttle)
- 1 futaba 9206 (rudder)
- 2 futaba 9650 (elev)
- 1 futaba 136G (gears)

Flying at least 14 min per flight I draw something between 200-300 mAh per flight. I use two packs of NiMH 1100 mAh.

Eggert, it is true that we add more components that can fail. But it is important to consider the topology of the system that is built. These components are added in parallel - this means that they can save a plane in case of a failure (switch, wires, joints, battery).

The only single point of failure that still remains is the RX... :)