RobinLeblond

Hello All !

First, here is what I was using for years without any problem, and after what I ask your opinion for.


I was using two lipo 2S 7.4v 2500ma connected in my Smartfly Super Reg and then the Super Reg to my receiver (through 2 receiver slots). And I have a BIG lipo 2S (30C, 5000ma) for the turbine.


Yesterday, one of my (receiver) lipo died. Here is the question: can I use the big turbine 2S 5000ma with the small lipo 2000ma as input in the Super Reg ? (it is mainly for saving weight and space.)


Is the power drain from the turbine pump/glow plug will affect my setup (receiver and servos) ? Is the setup (receiver and servos) will affect the pump action ?


If it’s ok, should I connect the ICS in the Super Reg (I guess not) or directly to battery (meaning the battery will be connected through a split cable to the Super Reg) ?


What do you think?

(PS : It is a Jet Central Rabbit turbine setup (not kero start))


Thanks,

Len Todd

Anytime you parallel two batteries, they should be the same capacity, voltage and S rating. The manufacturers also say the batteries should be the same age. But, I have used a new one of the same type with an old one w/o any detectable problems.

As you know, the turbine really sucks the current during starts and uses very little power when running after the start. After a couple starts, you could see voltage sags during starting that could impact the SmartFly. And, ... after several starts the two batteries will try to equalize voltages. With the Smart Fly coupler in there, I am not sure how that would be impacted. I know SmartFly tells you not to do what you are suggesting on their Bat Share, which I imagine is basically the same as what you have.

RobinLeblond

I thought the Smartfly was to avoid unbalanced batt problem. I thought that both batt input were isolated from each other?

ravill

My Feedback: (11)

Robin,

I set up all of my jets in the fashion you describe. It works flawlessly. Two 2S lipo's to the turbo Reg with one Lipo "y"-ed to the turbine. If my jet has smoke, I "y" the other Lipo to the smoke system.

The only problem I've ever encountered was when I hooked up one 3S and one 2S to the Turbo Reg. The 2S never got discharged. And the higher voltage from the 3S lipo turned into less amperage available.

So, I say, as long as you have the same voltage batteries hooked up, you should be fine. It is a back up, redundant system. You will be checking your batteries often and making sure that the voltage drops run accordingly.

speedracerntrixie

My Feedback: (29)

Agreed, I have run Smart Fly products on IMAC airplanes for years. The Turbo Reg will always pull form the battery with the most capacity. This is why Robert suggests using the same capacity batteries. If the same capacity the regulator will alternate between the two. If different capacities are used it will pull from the larger and then the smaller will just go along for the ride unless a failure of the larger occurs then the reg will pull from the smaller alternate battery.

RobinLeblond

Great !

Everytime I open the canopy and see those 3 batt of the same volage I wonder "why the ... should I have 3 batt?? It's kind of a little bit overkill !".
But I still want to keep the redundancy for obvious security reasons, but 3...

I will do some test before going "on air" with this, but thank !

Len Todd

https://www.smart-fly.com/Products/B...are_Manual.pdf

RobinLeblond

Thanks, I had the Super reg manual, but not this one (which better explain the batt sharing process).

rhklenke

My Feedback: (24)

Its not capacities of the batteries (which the regulator can't measure) that matter, its voltages. The Supereg (Turboreg) draws from mainly from the pack with the higher voltage until its voltage goes down and then it will draw from the other pack. I'm not sure if its an analog switching mechanism (which I would suspect it is) or a digital one (not as likely). The bottom line though is that if both packs are the same number of cells, same capacity, and relatively the same health, it will tend to draw them both down equally.

If the batteries have the same number of cells, but one is higher capacity, its voltage, under load, will tend to be higher, so the regulator will tend to draw mainly from that one until it gets low on charge - or at least lower than if the packs were equal. At that point, it will start drawing from the smaller pack. This is true as long as both packs are healthy. If the larger pack has a cell going bad however, its voltage may be lower and thus the regulator may draw from the smaller pack first.

If you use a 2 and a 3 cell pack (I wouldn't do that), it will draw from the 3 cell pack exclusively until its voltage totally collapses and then switch to the 2 cell one. At a minimum, this is going to over-discharge your 3 cell pack...

I think what you are suggesting for your setup is fine - as Rav suggests. When your turbine is drawing more current from its pack (starting, high throttle settings, etc.) its voltage will go down and the smaller pack will pick up the load. Otherwise, the larger pack will likely be the main source for both functions. What you'll need to watch for is how fast the large pack that supplies the turbine and the radio discharges in this setup and make sure you keep it charged. If it gets too low in flight, the smaller battery will take over the radio function, but if the voltage gets too low to run the ECU, you're dealing with a dead stick, which is generally not fun in a jet...

Bob

RobinLeblond

Bob, that's a good point ! So, a better setup should be to have two medium pack of the same capacity (let say 3000ma, 30C) (one Y ed to the ECU (and the reg) and the other alone in the regulator.)

That's bring me to a NEW QUESTION : How big is your ecu batt ? Mine was 5000ma, but was a lot overkill I think... What about your setup (keep in mind that I run a Rabbit, small to medium turbine class)...

rhklenke

My Feedback: (24)

Well, I still think you'd want a larger capacity for the one battery that is doing two functions - its going to have a larger current draw over each flight, so a larger capacity is warranted. If your engine is kero start, the additional energy drawn out during starting can be significant. You just want to make sure that the battery that is doing double duty doesn't run out during flight. Its backed up on the radio function, but its not backed up on the ECU function, so if you draw it down too far - poof, dead stick...

I use a 3700 MAh, 2-cell pack on my ECUs and 2, 2-cell 1750 MAh packs on my Smartfly regulators. I generally recharge after 3 or 4 flights (which is one day's flying at my local field - I do get 6 or 7 a day at flyins sometimes...). There's usually 50% - 60% capacity left in the batteries after 3 or 4 flights, but my engines aren't kero start...

Bob

ravill

My Feedback: (11)

My kero-start turbines get one battery to themselves.

Otherwise I share two 2500mAh 2S packs.

Sparhawk

I used to run the same set-up.
I have since ditched the lipos in favor of LiFe packs that I run direct into the smart-fly expander. No switches, no regulators.

Dan

melvin

My Feedback: (3)

In the opening post the gentleman declares one of his lipo's died. He doesn't tell us if the batteries are the same age,same brand and if they have been used exclusivly in this airframe. One could have been sitting on a bench for a year and the other in a 3d aerobatic plane. Let's assume they were in the same aircraft the whole time for a second. If one battery died what's to make him think the other one isn't too far behind!! If it was me in this situation i would replace both batterys with reputable manufactured batterys and replace the turbine battery at the same time. The turbine battery should be a Life battery because that is what jet central supplys when you purchase a new turbine. Batterys are cheap compared to total loss of a jet due to a dead stick or a brown out on the reciever. Go first class or stay at home

4ptroll

My Feedback: (35)

I would call Robert Richey at Smart Fly (Quest Engineering) and ask him directly. He's a great guy to deal with and full of information on his products.

Then you can report back to us

RobinLeblond

Melvin, the batteries was not those provided by JC. The one which died was the one I use during winter for any test on the "table". So it's kind of normal that THIS ONE died first. But you are right, I will change it to. The goal was not ot be cheap nor to do recup. It was just to better understand and to reduce weight and space (as I will be a little tight in the next project).

4ptroll, I may not CALL him, but if you can help me to find his contact info (meaning email), I will write him and ask a few questions for sure.

I will do some testing this winter and some more complete tests next summer.

Again, thanks all for your help,

ravill

My Feedback: (11)

I now place a date (month/year) on my lipos when I buy them, and replace them every two years or/if they start dropping voltage prematurely. I check my voltage before EVERY flight.

I've already learned my lesson with dying Lipos.

4ptroll

My Feedback: (35)

Quest Engineering & Development, Inc.
6125 South Ash Avenue, Suite B-8
Tempe, AZ 85283
Ph: (480) 460-2652

you can email SmartFly at the following:
[email protected]

Product Link: https://www.smart-fly.com/Products/Regulator/3.htm

I use the Turbo reg in all my aircraft and love the unit.

rrritchey

You can do this. The BatShare in the SuperReg will use the higher voltage battery (unless they are
within about 0.050V in which case both will be used at the same time). The input voltage to the
SuperReg should not exceed 8.5V. I know the directions say higher voltages can be used up to about
13V but I really do not recommend it as this means the current rating of the regulator is derated (reduced)
to about 25% of its stated current rating (about 2A at 13V vs 7.5A at 8.4V in and 6.0V out).
Personally, I would not do this on my jet. To many factors involved. I would just use a couple 1500-2000
on the SuperReg just to be sure I had my redundancy even if a battery failed and a turbine battery separate.
It really amazes me that so many people want to save 2oz or a bit of room and risk something worth $5000
to $10,000 on the cost and weight of a $20 battery. I see this all the time but still have trouble understanding.

rrritchey

The input voltage to the TurboReg should not exceed 8.5V. I know the directions say higher voltages can be used up to about 13V but I really do not recommend it as this means the current rating of the regulator is derated (reduced) to about 25% of its stated current rating (about 4A at 13V vs 17A at 8.4V in and 6.0V out).

rrritchey

I keep the switching simple, special very low Vf Schottky diodes. If both packs are equal voltage both diodes are conducting. If they are different then only the higher voltage conducts through that diode.

mauryr

Sorry to revive an old thread, but I am a little bit curious as to find out why you think this would be risky:
Personally, I was looking at this thread because with the 3 batts. setup, the turbine batt is single and not redundant, so if it fails, the engine will shut down.
I was wondering what can cause issues with the output from a diode based battery coupler Yd into the ecu.
I understand there could be feedback currents from the ecu itself or rf noise coming from the pump, so maybe add another diode to this Yd line wouldn't hurt, but besides that, what could happen?
Do you care to elaborate?

Thanks!

rrritchey

This is old and I did re-read it but let me take a stab at this. It seems you are asking only about the ECU and you could use a BatShare into the ECU depending on the current demand. Instead of running one big 5000mAH on the ECU you could use a BatShare Ultra and run two 2500mAH batteries into the ECU. Then if one battery failed the other would keep the ECU running. This thread was mostly about sharing the ECU battery with another battery for the receiver. Usually the ECU has a battery voltage higher than 8.4V which causes a problem for a regulator or most receivers. Also, diodes provide no noise protection, only reverse current protection. Don't know if this helps.

mauryr

What I was thinking was more on the line of:
1) a HV setup (rx and servos)
2) a single coupler (batshare or other diode based coupler that can withstand enough current, say 20A)
3) 2 bats, such as 2x2500 mAh straight into the coupler
4) one exit from the regulator, which would power the radio bus and the engine, all at 2S unregulated

If the issues are possible reverse current (would it be eaten up by the servos?) and rf noise, is the latter the only real reason why this setup would be risky, or is there something else to worry about?

rrritchey

I will say that as far as I know, an ECU is much less noisy than a gas engine ignition so RF is less of a concern. I guess the only concern here would be a shorted ECU which could then rob your receiver of power. In my opinion, its best to keep the radio redundant and separate from what ever the engine uses for power. That way you have a better chance of getting the plane down if something happens in your engine system.