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HomeAircraftHelicopterAerial Photography and Video › Battery Redundancy
10-26-2006 10:51 PM  11 years agoPost 1
TCGliderguy

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Albuquerque, New Mexico

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To follow up on something that AceBird said in the "Maintenance" thread.... and I am ASKING the question, not stating an opinion....

>Using two batteries is not redundancy by themselves. It would require some kind of monitoring and switching circuit to provide any advantage at all. It is a bad idea to just put two batteries in parallel (it seemed like this was the case for one example).<

I recently found myself refereeing a heated argument on this subject. There are a number of products on the market that will provide the switching, between two battery packs... as AceBird suggested..

On the other hand, Red Scholefield (who is often credited as being the Battery Guru in the R/C hobby) has his http://www.rcbatteryclinic.com website, and openly recommends plugging two packs, each with its own switch, into two channels of a receiver. He even says that the packs don't have to be the same current rating... just the same voltage.

If you go to his website, in the frame on the left side is a link titled Parallel Operation = Reliability and Flight Time.

I'd be very interested in hearing your comments on this subject....

Thanks!

-Taylor

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10-26-2006 11:13 PM  11 years agoPost 2
Brett Horton

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I am going to start this thread of with AP ship Maintenance ideas.......wait.... never mind...

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10-27-2006 01:38 AM  11 years agoPost 3
rroback

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Irvine (UCI), Ca

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I used two 2300mah 4 cell nimh packs on my maxi for a while, with dual switches. Now I've got a lead I made up with 3 servo connectors ( plugs into receiver) and ends at a deans ultimate, and I made a 4 cell, gp2200 receiver pack, with deans.

Rhett..... I can't fly, but the Profi sure can.

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10-27-2006 03:56 AM  11 years agoPost 4
Wayne Mann

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United States of America

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I was told by Futaba to use two packs with two switch harnesses just like I described in the other thread. The only thing that could get you in trouble with this set up is if one battery shorts out. I have also talked with another person about this and I trust his opinion on anything electric.


Wayne Mann

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10-27-2006 04:32 AM  11 years agoPost 5
Toadster25

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Iowa

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If nothing else it would save you if a switch goes bad or battery comes unplugged. Might even help in a crash if one battery gets thrown off the heli and unplugged atleast you might still have control to kill the engine rather than stuck at full throttle and dacing around on the ground.

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10-27-2006 05:22 AM  11 years agoPost 6
GauchoVolador

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Tx

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Had bad experiences with switches. Two batteries on spare channels work really nice.
We use No switches One battery, the only drawback is wearing out the extension and the battery connector.

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10-27-2006 06:30 AM  11 years agoPost 7
CKY

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Sunshine Coast, BC, Canada

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I like the two batt/switch config also. I find it will give the optimum current to the rx, which in turn feeds the servos. If using digital servos I really notice the improved voltwatch reading.

Very cheap insurance.
Chris

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10-27-2006 05:47 PM  11 years agoPost 8
AceBird

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Utica, NY USA

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On the other hand, Red Scholefield (who is often credited as being the Battery Guru in the R/C hobby) has his http://www.rcbatteryclinic.com website, and openly recommends plugging two packs, each with its own switch, into two channels of a receiver. He even says that the packs don't have to be the same current rating... just the same voltage.
Oh Darn … again I find myself saying something that conflicts with an expert except this expert I have great respect for. The following is a few clips from his document.
The use of redundant parallel fight packs is an excellent way to increase the available flight time and significantly improve the reliability of the on power system.

The dual redundancy concept is to protect against the failure having the highest probability - that being the circuit path from the battery to the power buss in the receiver.

These concerns show a lack in the understanding of the charge and discharge potentials involved in Ni-Cd cells.

Parallel charging of Ni-Cds is not recommended
I know you all have made up your own minds but let me give you a couple of things to think about.

1. I think the highest probability of a power failure is flying with a dead battery. I have seen it a hundred times, you’ve seen it a hundred time. People take off thinking they have enough left in the pack and it doesn’t make it. THIS WOULD NEVER HAPPEN TO RED SCHOLEFIELD.
What happens if one battery is not up to snuff? True the good battery won’t charge it but the weak battery will put a load on the good battery so the system goes dead even sooner! With a nitro you stand a better chance of getting away with it because of the shorter flights. Not so with a gasser. We set our timers on the transmitter thinking we can make it to the end.

2. If I take a single pack that has the same capacity as the two he suggest and put two switches and two inputs to the receiver then I have accomplished the same thing (failure of the circuit path from the battery to the power buss in the receiver).
But I have also decreased the probability of failure because I only have one battery that can short, go dead or be at low capacity. Simple mathematics…
If you subscribe to the thought that eliminating the switch all together is a good practice you may or may not lower the risk of failure. At least a switch is designed to be connected and opened frequently. RC connectors are definitely not designed for that so you need a regimented policy for replacement to be safe.

3. Red has always been a proponent of Ni-Cd cells. So am I. But do all of you strictly use Ni-Cds? It would be a wrong assumption to take Red’s words on Ni-Cds and directly apply what he says to all the other battery technologies in use today.

4. I don’t think Red emphasizes the charging requirements of using two packs enough. You must not charge them is parallel and you must fully charge both packs if you use two or else the highest probability (power failure) will get you. You become accustomed to getting a certain amount of time out of your batteries. When a source becomes a sink you are in a world of hurt.

The last thing I would like to say is Red’s site is a great place to get a good understanding of battery knowledge. It surely has helped many a newbies, me included. Most of his information is for newbies getting into RC airplanes that typically start with the standard .40 glow. It would be great to get his opinion on the best battery circuit for a gasoline helicopter rather than extrapolate what he has said for other hobbies. I am thinking he would lean for the use of a generator. But maybe I am wrong. Anybody know him personally?

Ace
What could be more fun?

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10-27-2006 06:21 PM  11 years agoPost 9
aambrose

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Pana, IL

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OK, so what's the best way to charge dual Rx packs? Individually? That's how I've always done it but it would be nice to be able to charge both at the same time to save time. I always charge both packs (ie. if I charge one, I charge the other too -- just not at the same time). I realize a separate charger for each pack would do it, but I'm wondering if there is a safe reliable way to charge both with one charger.

Thanks!


Tony

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10-27-2006 06:39 PM  11 years agoPost 10
Wayne Mann

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United States of America

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First off this is about aerial photography and not 3D or endurance flying. It is rare that I would fly for more than five minutes at a time. We get up, get the shots and get down. I check both packs individually before each flight with a one amp load. I also charge both packs individually. Once the batteries dip below 4.8 volts they get charged back up. There is a ton of battery left in both packs if you do not dip below 4.8 volts under a one amp load. That is the other part of the saftey in using two packs in that I get twice the run time which means that I can usually get about 5 flights if I stay around the five minute flight time or less, without going below 4.8 volts.

"edit" I should also mention that I cycle these batteries probably every twenty charges or so.


Wayne Mann

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10-27-2006 06:57 PM  11 years agoPost 11
CKY

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Sunshine Coast, BC, Canada

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I have an old Alpha 4 charger so multiple packs is not a problem.

Trying to charge two packs in parallel can cause some grief, especially if both packs have not evenly discarged. I smoked a wiring harness by trying to adapt a plug to charge both packs at the same time. When the smoke cleared I decided to never try that again.

As far as shorting packs go, it happens, but usually gives you a LOT of notice if batteries are monitored (voltwatch) and cycled on a regular basis.

I am not familiar with LiPo's, bec's, etc. for electrics. They will have their own set of issues. For good old fashioned 4.8 volt systems a monitored 2 pack system almost eliminates any power issues for the heli controls.

The less you have to concern yourself with during a shoot the better.

Chris

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10-28-2006 01:02 AM  11 years agoPost 12
AceBird

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Utica, NY USA

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I'm wondering if there is a safe reliable way to charge both with one charger.
You plug them in series and set your charger for 8 cells instead of four. In order to insure that they are at the same level discharge both packs to the cut off point and then charge them. But remmember you now have 8 cells total so the chances of getting one off balanced is greater.

Ace
What could be more fun?

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