BarracudaHockey

My Feedback: (11)

Wow. Mythbusters time.

1. 2 batteries, two switches, works perfectly. Unused servo ports first choice, Y harness to another channel works, but my first choice is an open channel.
2. Power board not needed for something like this.
3. Pam is right, batteries don't short and they for damn sure don't drain each other when and if they do, they "might" but it would take days not minutes that people that sell battery isolators imply.
4. Any servo rated for 6v (5 cell pack) will run on an A123 pack w/o any problems.
5. Twisted servo extensions do nothing for RF rejection, they look nice, but thats their only benefit in RC.

Did I miss any?

Teus

Just deleted all my input in this thread, Thanks.

pkoury

My Feedback: (7)

from post 20- "Remember when digital servos are used, they can all be moving at the same time. Analogs are sequential".

Huh?

Don't know what brand radio he is using but I have never had a radio of more than single channel that moved the servos sequentially.

Bottom line is I agree with BarracudaHockey, keep it simple.

Frank Ts Stuff

My Feedback: (130)

Here is how I set up my models....simple setup.

1. 2 x LIFE batteries (A) feeding 1 x "battshare" (B) from "smartfly"
2. "battshare" (B) has two leads which then feed my RX (C)
3. notice I do not use switches.....I simply have make the final connection between the batteries and battshare (A+B connection) whenever I am ready to fly. I use the little servo keepers on these connections....

With the Paulisthina P-56, we had one with a ZDZ80cc for power (way overkill!), the connections will be easy to make through the cockpit door opening

-Sean

PS - on a more complex model, like my Vailly Tempest, I still keep it very simple but with more connections. I have 2 x recievers, 2 x battshares, 3 x LIFE batteries. Each LIFE battery has 2 x output leads and I use both leads on two of the batteries to feed the two battshares (4 connections). Each battshare is split between the two recievers with one lead going to each. The third battery is for my ignition (1 connection). When I go to fly I have 5 connections to make which takes me less than a minute.......

PPS - be careful with those 3305's. We had a few fail and after discussing with Futaba (as it appears you have also) we were told that they are designed for RC cars and do are mfg'd to a lower tolerance than servos for planes...

acerc

This is all true, but, not the only reason for what most are referring to when thinking redundancy. As a big scale guy myself I understand quite well that two batteries are just an extension of flight time, nothing else. But there are those that lack the knowledge yet that true redundancy is, in conversation, for the entire system. In my 3-10K builds my redundancy is for a servo going bad, or a switch failing, and even for that one in a thousand battery going bad. With a power board one can obtain a constant throughout the system with separating circuits in the event one of the afore mentioned parts go bad, short, or just die. Many, if not most, of us have experienced a servo going out for what ever reason. With the amount of money and time we are putting into these airframes a little extra security is a smart move. Of course one can argue what are the odds, but, for me I would rather cut those odds down as much as feasibly possible. I have had the power system I use save a couple planes by isolating a servo. of which probably saved me a few thousand dollars. Is any of this a necessity? No! But a very good option.

landeck

My Feedback: (1)

Sorry Drac1, A123 batteries are 3.3 volts per cell and are a type of LiFe battery with a patented manufacturing process which is designed to produce a better cell.

Bruce

dbsonic

My Feedback: (3)

Off topic, but technically Teus is right regarding servos and over-voltage. You have to look at specs for any servo and go from there.
Operating a 4.8v/6.0v rated servo on LiFe is technically risky for a number of reasons. In the case of Futaba, reps have stated this in the Futaba forum and part of the reason they designed the HV series of servos which spec both LiFe and Lipo nominal voltages. Empirically many have found the LiFe combined with 4.8/6.0 rated servos to work likely owing to the fact that reputable electronics companies design and characterize for margins beyond nominal conditions. How much of a margin depends on each company but often a max of 10% on the voltage aspect of the DRCs is the rule of thumb in the digital world (barring waivers).

BarracudaHockey

My Feedback: (11)

6v ratings mean a fully charged 5 cell nickel battery, which is what A123's operate at.

speedracerntrixie

My Feedback: (29)

I remember when the popularity of using 5 cell NiCad/Nickel batteries gained speed that there were a good deal of servos that were having issues. Now with the increase in voltage with LiFe and A123 this is somewhat a replay. Futaba allegedly has a certain RX that has a regulator that will go into thermal shut down if used with a Life pack. Sounds to me a regulator is a good idea, Yes one additional failure point but over volting servos and RX would be at least 5 possible failure points.

drac1

My Feedback: (4)

I'm not concerned, just curious. I don't regulate 6.6 volt packs.

Thanks.

drac1

My Feedback: (4)

OK. But how do you explain this?

BarracudaHockey

My Feedback: (11)

A123 are Lithium Iron phosphate

thepamster

Drac, go to the actual site and read what it says and pay attention to volts/cell at the bottom of the pages.

jwrich

My Feedback: (17)

I have the Hitec Aurora 9 with Optima 7, 6 & 9 receivers. I fly WW I 1/4 scale airplanes, with Hitec 645 and some Power HD 1501 MG, standard servos for the throttle, all are analog servos. Recently I began replacing my receiver batteries with Life batteries with 2 switches, 2 batteries, plugged into 2 ports in the receiver or a y-cord as needed. A friend suggested I plug one switch into the normal battery port and the other into the SPC (Supplementary Power Connection) port. His reasoning was that if one battery failed the other would not drain the other battery. In this configuration, when the system is powered up one switch powers the receiver and the other powers the servos. He said should one battery fails the other battery will still power everything. Using this configuration, I don't understand how this would work. Your thoughts on this please.

Thanks
Rich

BarracudaHockey

My Feedback: (11)

Simple, one battery doesn't drain the other if one fails. Even if they are plugged into each other directly, it will take hours.

radfordc

My Feedback: (14)

You've made the statement...now provide the evidence. What happened, when, etc. How did you know the battery shorted and that this caused a crash?

speedracerntrixie

My Feedback: (29)

I too use an A9 and would never hook up anything to the SPC unless flying an electric airplane and want to use the SPC for it's intended purpose. The SPC has a built in regulator and with a 6V pack you may not be getting enough voltage through the reg to power the RX.

Lightspeed1551

My Feedback: (4)

+1

speedracerntrixie

My Feedback: (29)

+2, For the last 8 years everything I build 100cc and larger has gotten an Expander. Can't say enough about the Smart Fly products.

BarracudaHockey

My Feedback: (11)

Good stuff, but way overkill for the OP's proposed use

Flyfast1

My Feedback: (1)

I hope this is not too off topic, but since the Futaba 3305 servos were discussed in the thread, I thought I would mention that about two years ago I did my own testing of a few different servos that I have used in my warbirds over the years, including the Futaba 3305, Hitec 645mg, etc., and the 3305s drew much more current than the other servos, both with no load and when loaded. I built a test jig and applied several different loads to each servo and measured the current draw. I would have to go dig up the paper on which I recorded my test results, but I recall the Futaba 3305 had 3X the idle current of a Hitec 645mg and more than double the current draw when loaded. On their website, Futaba for several years had a table that indicated that the 3305s are not appropriate for use in aircraft. I corresponded with them about this and never received a detailed explanation, but perhaps the current draw was a factor in their usage recommendation. The difference in current draw is probably less of an issue with modern battery technology, but maybe there were issues when used with older NiMh battery packs that had high internal resistance?

-Ed B.

Flyfast1

My Feedback: (1)

For those that use the powerboard type products (of any brand) with two battery packs, is only one battery pack electrically connected to the output of the powerboard at any given time? I looked around the SmartFly Website and didn't see answer to this. I didn't read all the information about all their products, so perhaps someone here knows the answer.

Thanks,

-Ed B.

Boomerang1

drac, easy to answer! I don't know.

Keep in mind too that the examples I gave (and backed up by bench testing) are based on nickel based cells which are nominally 1.2 volts per cell.
The shorted cell example I gave was based on the very unlikely chance of just one cell shorting in the pack, probably a ten thousand to one chance.
The voltage drop (minimal) & the current draw involved (very low) is because the voltage difference between the two batteries is very low, just 1.2 volts.

That's probably the only scenario worth considering, the chances of two cells, in the same pack, suffering the same type of failure (shorted cells) at
exactly the same time would have to be ten thousand times ten thousand!

Your situation is different because I read you use Li-Fe two cell packs which give 6.6 volts. if you suffer a shorted cell the difference will be 3.3 volts
between the good & bad battery, twice as bad as the examples I gave. I don't know if regulators would protect you from that.


My experiences with regulators is limited mainly because I still use Ni-Mh batteries which don't need them. I have made my own simple regulators
so I can run servos from electric flight 3 cell packs & I have used the Powerbox regulated switches with Li-Fe batteries only because I forgot my
usual batteries & had to improvise something to allow me to fly at an interstate jet meet.

I'd rather tell you I don't know the answer than give you the wrong information. Perhaps the (many) manufacturers of regulators can help? - John.

abufletcher

A terminology question: As people are using them here are the terms "powerboard" and "regulator" the same? (And is the BatShare a "regulator?")

speedracerntrixie

My Feedback: (29)

A power board is a device the will supply power to the servos and lets the RX simply handle signals. In some cases it will have a servo matching device included as well as a regulator and Batt share. Regulators simply reduce the voltage to a set level, mostly 6V. If running Lipo or Li ion batteries without HV servos a regulator is a must. A Batt share is a device that allows you to use 2 RX batteries and isolates the batteries from one another. Some powerboards ( Such as the Smart Fly EQ6 Turbo that I use ) has all these features built in. For more detailed information you can visit Smartfly.com