One Battery or Two??
 

How many of you 35% plane flyers out there are using only one (1) flight pack battery? I think most of us only use one (1) ignition battery so why not only one flight pack battery?

I welcome any and all responses, comments or debates one why or the other.

Bobby

RE: One Battery or Two??
 

Use 2 batteries and 2 switches. The extra switch doesn't weigh that much and gives you redundancy on the part of the system most likely to fail.

Instead of using one 4000+, use 2 2000+ batteries (you get the same flight time and weight, with added switch redundancy)

RE: One Battery or Two??
 

Hey Bobby. If its a plane over 30% I diffinatley use 2 batteries and switches. Personally I use 2 batteries, 2 switches, and 2 recievers. I will never fly my contest plane again without 2 recievers. I am the poster child for that. My antennae wire pulled out of the receiver in flight. If I had 2 of them I could had made at least a bad landing. Thats just my personal feelings on the approach to a big plane. 2 receivers!!!!....;)

RE: One Battery or Two??
 

Thaks Scott. The antenna on my AW 260 in all internal so the danger of it getting pulled out is minimul I also started using the synthesized JR receiver to keep breaking of the crystal to a minimum (ha, the synthesized RX has NO crystal)!!

But I did sling the ignition battery loose and had a dead stick a couple of weeks ago due to a severe left snap roll. That is where I came up with the question about one or two RX packs. I think our battey/switch equipment is so much better these days that the odds of a failure get less and less. BUT, how much less allows us to use only one receiver battery? That is the question!!!

Bobby

P.S. That's all for tonight - I'm hongery!!

RE: One Battery or Two??
 

Hi Bobby and Scott,

You guys probably now the most common reasons a plane crashes besides our dumb thumbs is because of switch and battery failing. There are switches on the market that fail in the on position only so that takes out the switch problem. Using two batteries allows the amp load to be split between them. JR type plugs that most of use are only good for about 3 amps. I would be willing to bet that your plane pulls that much during some high control deflection maneuvers. My vote is with two batteries and deans plugs (if able) on 33% planes and larger. That’s my 2 cents LOL.

RE: One Battery or Two??
 

You can always land a plane with no motor due to ignition battery failure........but you can't do anything but pick up the pieces of a plane after it crashes somewhere due to battery failure (whether by age or operator error)

RE: One Battery or Two??
 

35% Plane to me means a $3500 investment. As Sweatpea states, ingnition craps out, deadstick, we have all the time, warbirds, pattern , heli's, etc etc etc and most of the time, with practice (heli's) you still have flying surface control and can usually land w/o incident.

However, For $50 bucks, that bad cell and subsequent uncontrollable crash could have been prevented with redundency. I also fly 2 rcvrs in anything that size or bigger. In addition to redundancy (forgot to turn one switch on my extra 7 years ago and it flew fine, just snapped a little slower) it makes routing the amperage easier without useing the new fancy power boxes.

My $$ is important to me so I spend a little extra, use quality parts etc etc.

Ed

RE: One Battery or Two??
 

Bobby Just buckle down and get a 40% you know you want one, they fly slower, present better, and are easier to see.

RE: One Battery or Two??
 

Yes and no. I probably need to put the 3W prop back on and use better throttle management to slow my AW 260 down more. I have too much $$ invested in 35%/100cc size planes. Besides a bigger plane implies a larger engine which implies larger props which implies a larger trailer which implies a larger truck to pull the larger trailer which implies more $$.

I'll just stary will my little (ha!?) 35% planes and do better throttlemanagement and work on my presentation skills. I'll show youse guys!!


Bobby

RE: One Battery or Two??
 

I bought a 800lb 5x8 wells cargo v-nose (10' down the cetter of the V). With a shelf it will haul 2 40% planes and I pull it with my 4cyl Car.

RE: One Battery or Two??
 

Most of the FAI guys in the Uk are using a single 4300 5 cell battery with two leads into two switches these days, even if one cell goes down you still will have a 4 cell battery as long as its not shorted out, as someone said our batteries and switches now days are far more reliable than they used to be, just use heavy duty wire and switches, incidently in over 40 years of flying RC I have never (yet) had either a servo or switch fail in flight, had them but always noticed on the ground or during maintenance which I do a lot of.

Mike

RE: One Battery or Two??
 

I thank all of you who have responded to my question of 1 vs 2 batteries on this forum as well as the SA and SCIMAC forums. I will complie the "data" and present my conclusions within the next several weeks.

Again, thanks for providing me with practical infomation.


Bobby

RE: One Battery or Two??
 

Oh come on now Bobby. I have to be more financially challenged then you.;) But I still bought that "slightly" :) crashed 40% at our IMAC the other day. It may take be 11yrs, LOL..... to get all the funds to get her flying again. But If I can do it................................................ ................
Redneck Shaun

RE: One Battery or Two??
 

way to go shaun [sm=thumbs_up.gif]now dan can haul your plane around:Djust kidding dan

RE: One Battery or Two??
 

This is true, but you need to know what it means. The amperage rating for a connector means that it can handle that load continuously without a rise in temperature. It does NOT mean that the connector fails, overheats, etc.

Also, FWIW I have determined, and confirmed several times that my 11 servo 38% Extra draws an average of 3 amps, so split it is 1.5 amps average per battery. Emcotec setup a plane with a data recodred and got an average load on a 14 servo aerobatic plane of 3.2 amps, with a couple of short-lived peaks of 20 amps (20 milliseconds long).

Just some real world data worth knowing.

RE: One Battery or Two??
 

3A average per flight? You've got a real problem if that's really the case! You shouldn't be exceeding 1Ah average for the entire flight (assumed a 15 minute, energetic 3D flight). This, based on actual readings from flying a 40% Carden Extra with 8 digitals (600 mAh avg) and extrapolating to your 11 servo setup. Better check for some serious binding or mis-adjustment in yout servo centering/endpoint/tracking linearity with any ganged servos.

RE: One Battery or Two??
 

Duplicate or Eliminate any single point failure.

I have CD'd 6 IMAC's and seen redundant/batteries/switches/regulators save a 40% plane and seen dual Receivers also save a 40% Plane. In one instance the battery connection came loose in the pack, and in the other instance a single reciever went into failsafe and the plane was landed on the other receiver.

Yes you can, if wired properly, make a single pack/switch/reg provide enough current, and will probably never fail. But it is then a single point failure.


I wont risk it on my 28% much less my 42%.

RE: One Battery or Two??
 

No, the AVERAGE LOAD is 3 amps at any given time during the flight. Not the average CAPACITY used. So a 15 minute flight would consume +/- 0.75 amp-hours from the batteries, or about 50 milliamp-hours per minute of flight. I will use up +/- 3,000 milliamp-hours of battery in an hour of flying. With two 4800 packs 9,600 milliamp-hours of total capacity on board I can get around 12 flights pushing the limits.

RE: One Battery or Two??
 

Good advice.



How is this possible?? PCM failsafe on one RX but not the other?? How can one RX get interference, but not the other?? Either they are getting a good signal or they are not. I cannot see how one can and the other can't. I suspect something happened to the other RX and that it did not, in fact, go into true failsafe.

Remember, the TX is ALSO a single failure point. Oddly enough I have NEVER had a modern RX fail on me, but I have had THREE TXs die on me. All on the ground, but I have seen TX failures in flight too. Not pretty. Redundant TXs anyone??

RE: One Battery or Two??
 

OK, so if you were actually experiencing a 3A average load, you would be using 12Ah per 15 min flight. I think something isn't being reported correctly or maybe is being misinterpreted from the logger. Anyway, this is just a matter of getting terminology straught. At least you confirmed that things are running normally.

Sorry for getting things off track a bit, this is derailing the question of whether to use one pack or two. I would always go with two for anything I care much about. I recently did a pair of 2M pattern birds with dual LiPo's each. Of the 4 new LiPo packs I bought, one had an intermittent connector, right out of the package. It was a problem with the way the wire had been crimped to the connector pin. It worked most of the time, but in my normal bench testing, I caught it. Even so, it could have easily gone into an airplane and caused a crash if it had been a single battery setup. Murphy is there all the time and I like to go with some backup to try to defeat him.

RE: One Battery or Two??
 

No, if the load is 3 amps for 15 minutes then that consumes .75 amp-hours of battery capacity. NOT 12 Ah. 3 amps for an hour is 3 amp-hours, not 180. Put a 3 amp load on a 3 amp-hour battery and it will be fully discharged in 1 hour.

The load is in amps. The battery capacity is in amp-hours. Capacity divided by the load determines duration of the battery.

You are confusing loads with capacity and incorrectly calculating them both.

RE: One Battery or Two??
 

OK, try calculating a cross country trip this way, using gas instead of electrons. If you're in a car, bring a gas can, sunscreen and comfortable shoes. If you're in an airplane, bring binoculars (helps find your new landing destination). Let's not argue this OK? I'm sorry I got the thread off track.

RE: One Battery or Two??
 

I believe the receiver went bad don't know all the details, but it was sent back to the MFR and replaced.

Like I said before I have peace of mind with redunt packs, batteries, switches on my 28% and 33%, and redundant receivers as well on my 42%. I don't really care what the average current pull is. I fly and check my batteries under load after every flight. If I can get 10, 15 minute flights and still have safty margin I am totally happy. With $2000 to $7000 invested in each of my planes I am not taking any chances.

Duplicate or eliminate any single point failure.

RE: One Battery or Two??
 

I have CD'ed over twenty five IMAC type events, and have never seen a receiver, switch failure, or anyone land on one battery. The closest we got was a receiver that spit the crystal because the pilot mounted the receiver on the wing tube hence causing the "tape the crystal" syndrome. Not that it can't happen, but sometimes I think there is more hoopla then anything that actually happened. I just think of the famous line quoted by Mr Scott in reference to the newest Enterprise..."the more plumbing you put in, the easier it is to stop up the drain." this topic has been beaten to death many times over, but there are still some guys out there that insist that two receivers are necessary, and that off the shelf connectors are insufficient to handle loads - despite both being proven over and over to be hype.

RE: One Battery or Two??
 

Full scale aircraft have redundant systems to save pilots lives model aircraft have redundant systems to save our planes lives.

Flying without redundancy is like a fighter pilot without a parashute. 99.5% of the time the parashute will not be used, pilots can spend 20 years and never have to eject. But that one time that they do they are glad the shute was there. I don't care if My battery/connector will handle 100Amps, on giant scale planes for the safety of my plane and the personnell in the area I will run redundant power systems. A reciever is an electronic componet in a volitile environment. Electronic componets fail. The Mean time between failures could be 5000 hours, but I don't want a receiver in my plane that final hour.

Yes one battery, one receiver, one switch, and standard connectors will likely fly a giant scale plane and never have any issues the data shows this to be true. But would you want to fly in a comercial airliner with one battery, one pilot, one high capicity hydralic pump, one radio, one fuel tank, one engine etc..?

Dupilcate or eliminate any single point failure.