rustyrivet

My Feedback: (6)

Instead of me buying a 1600 MAH battery pack to power my 1/4 scale, can I simply y harness together two smaller packs? Say a standard JR 600 mah receiver pack, and a Sanyo brand X 1200 mah battery pack?

I want to make sure that mixing and matching any variety of RX NiCd packs will give the same good results and duration, without sacrafice of some sort.

Jazzy

Sure, you could do that.
They must be charged separately.
You'll probably find that using just the 1200 mAH pack will be sufficient. (Knowing the aircraft type, number of servos, and intended flying style would help.)

Depending on the circumstances, moving up to say 'A' or sub-C size cells might be beneficial in the long run.

Ask yourself this: Is my plane and all it's components worth a few extra bucks?

rustyrivet

My Feedback: (6)

Thanks Jazzy,

It seemed obvious it should work, but I just wanted to make sure. For some reaon, it seems most large rc planes I've examined always have one big battery pack.

Only once I have seen it done the way I mentioned with two seperate packs tied together, and I thought to myself "How novel. Howcome I didn't think of that!!?

sfaust

My Feedback: (11)

Most large airplanes that I have seen use two batteries, two switches, and are plugged into the receiver. This provides the same benefits that you cite, but also gives you independent power sources for redundancy. Should a pack or switch fail, you still have the other pack and switch working.

All you have to do is plug the second battery and switch into any unused port on the receiver. The receiver power leads are just a power distribution bus, and only the signal leads are separate.
Most switches with a charge connector separate the battery from the receiver, so you can charge both batteries at the same time, but they will be charged independently.

rustyrivet

My Feedback: (6)

Thanks Stephen,

I have heard about the benefits of redundancy mentioned in the past, but it didn't dawn on me that with the second battery I'm looking to add, that this is exactly what could now be easilly achieved with little extra effort.

I'm a guy completing his first 90" big bird that will have a Nelson glo driver, and a Perry pump added for extra safety. So this redundency system is right up my alley since I like the added measure of security. I need to add an extra battery anyway for the 6 heavy duty servos, so throwing in an extra switch too, won't make a big difference in overall weight.

Appreciate you knocking me on the side of the head to have me recognize what I should be doing.
If I have any more questions, I now know who to come back to, to get knocked on the other side of my head. In that case who knows what other smart gadgetry we could come up with to cram in this plane!!??

sfaust

My Feedback: (11)

There is little other gadgetery that is needed. The simpler the plane, the more reliable in most cases. Adding more gadgets adds more potential point of failure, which means less reliability. The biggest offenders in our planes are batteries and switches, with switches being the higest failure points. User error is second, such as not fully charging a battery, not measuring and understanding capacity checking, dumb thumbs, or missing items during the pre-flight inspections or maintenance.

The dual switches and batteries are really all that you need, with proper maintenance and pre-flights if it is built properly. Doing these things will go so far to keepting that plane reliable and brining it home after every flying session. The rest is up to the pilot not push too hard, get stupid in the air, or decide to miss a pre-flight or maintenance item to save time.

mulligan

One note not yet in this thread- when combining multiple packs, they must be the same voltage rating (i.e., the same number of cells).

- George

rustyrivet

My Feedback: (6)

Ok, let me see if I have this right: For redundancy, I can actually plug a second battery pack with a switch on it, into any remaining open channel in my JR600, JR700 orJR 549 receiver without damaging the receiver. Then I would simply turn on both switches and battery packs when flying? Right?

PS Stephen, you don't know me. I love building, but I'm still trying to get comfortable flying. I feel like flying my planes is more of an assignment I have to do to pass the course. I shake like a leaf while the plane's up there!!! They nicknamed me the "Deadstick King" at the field. Dead stick flying causes the hair on my back to pop through the weave in my shirt! Just what I need to calm me.

An ARF isn't too bad with mishaps and bad landings, but a year long project is a heart breaker. SO I WANT THE ENGINE AND ELECTRONICS TO STAY THE HECK ON! Hence, why I have the fuel pump, Nelson driver, and redundant battery system going in it. Maybe when I get more comfortable and confident, I'll throw away one or two of these crutches. Meantime, the extra few ounces seems like a bargain to me.

sfaust

My Feedback: (11)

Yes, you will not damage the receiver. Think of it this way. There are three pins for each servo lead that you plug into the receiver. The pins for the black wires are all connected together on the circuit board to the pins for the black wire on all the other ports. The same goes for the pins for the red wire, in that they are all connected together on the circuit board. The only pins that are separate are the white wires, which go to the circuits that control the output for each channel. Hence, it doesn't matter where you plug in the battery, since the reds are all connected, and the blacks are all connected. Here is a pointer for more info.

http://www.fly-giantrc.org/technical/parallelbatt.html

Using the two batteries and switches, you gain redundancy for the most common failure points. The switches, and the batteries. Lets say you forgot to fully charge one of the batteries, and during the flight it runs down. The second battery will take up the slack and keep on ticking. If a switch fails open, or one of the battery connectors pop out, you won't even notice it till you land safely. Its a great easy method of solving the most common electrical problems. Foolproof.

Couple of things. Always charge the batteries separately. If you use switches with charge leads, that guarantees that you can change them at the same time with separate chargers, and they will be charged independently. Second, always test them before every flight. Turn on one battery, and make sure everything looks fine. Then, turn it off, and turn on the other battery and check. Then turn on both batteries. Also, measure each battery with a loaded ESV meter before each flight. Do these things, and a power failure would be almost non-existent for you.

I know how you feel about the fear of loosing a year long project. While I might have $7,000 in the air during a flight, its not the money that bothers me the most. It would be the time lost on that project, that I could never regain, and the next 300 hours building a new one. When these things take on the order of 300 hours to build, you don't want to loose that much time and effort for some stupid mistake. Unfortunately, it can still happen at some point. There are no guarantees.

The pump on your engine, and the Nelson drivers are valid ways to solve your dead stick problem. The extra few ounces seem to be worth it in this case. If they are working, don't throw them away, since with your nickname "Deadstick King", it appears that they aren't crutches at all.

rustyrivet

My Feedback: (6)

Stephen,
Very informative web site. Appreciate the detailed input and time you've taken to help out. -Randall

strato911

Most switches only interrupt the positive wire, and if you charge the packs from two seperate chargers at the same time, there may be problems with the common ground (especially in dual-port chargers). Either disconnect one battery completely, or make sure at least one of your switches interrupts BOTH wires (+ve & -ve). This was recently discussed in this thread: http://www.rcuniverse.com/showthread...569&forumid=24]

sfaust

My Feedback: (11)

Your'e right Strato, I should have mentioned that.

I only use the JR Charge Switch every since I started taking switches apart to see what is inside. I am sure both the red and black are interrupted on these switches. I know the Futaba standard switch only interrupts the positive lead, because I hate the way the black leads are soldered together, then run right across and on top of the switch posts for the positive wires. Sure there is insulation, but there is also vibration. One will destroy the other over time, and I bet we all know which one will suffer

I also use the Alpha 4, which is a single charger with 4 ports. I am not sure if this charger is capable of handling the common ground, and thus why I never had a problem prior to using the JR charge switches. I've never tried to use anything else on dual battery setups, since when I first started seeing the need for redundant batteries, I saw the same need to get a charger with more ports. The dual batteries and Alpha almost came simultaneously.

rustyrivet

My Feedback: (6)

OK, professors;
before I finish mounting the two seperate Great Planes combination switch and charge jacks on the bottom of my fuselage, let me be sure I'm not going to have problems.

I'm using the Great Planes combination switch and charge jack plastic recptacle.
One switch I have on one of theses Great Planes recetacle is a Futaba, and the other switch on the other receptacle is a heavy duty JR switch. If you're familiar with this Great Planes jack I'm referring to, you know it mounts both the switch and charge jack nice and neat in a little 3/8"wide x 1 1/2"long black face plate. But theres no sence in using this style device if I can't utilize the charge jack feature of it.

So, if I leave one switch off, and hook up my standard accucycler to the other receptacle will I have problems? Or did I understand that charging the two batteries using the two seperate recptacles as I will have them might work ok if I change out the one Futaba Switch to a JR switch? ( and have two Jr switches)

If I still have to manually reach into the fuse to disconnect one battery pack, then there will be no sense in me using these Great Planes switch/jacks which will be pretty looking, but useless. (pretty useless)

strato911

As long as at least ONE of the switches interrupts both wires, you can charge both batteries at once without concern. :thumbup:

Since I wire up my own switches, I don't know the specifics of Futaba and JR switches, but previous posts by sfaust indicate he has researched it thoroughly (JR cuts both wires apparently). If you have any doubts, you can verify the switch interrupts both wires by testing for conductivity of the individual wires while operating the switch.

rustyrivet

My Feedback: (6)

Dennis,

If worse comes to worse, I'll hold off on mounting the two receptacles on the fuse tomorrow, and first play around with the electrics of the switches, checking continuity as per your mention.

Unless Stepen might know. But this might be tricky for anyone to visualize and know what's going on unless they actually have the plane in front of em with everything there to check out.

Appreciate it.

rustyrivet

My Feedback: (6)

....the bottom line, according to that informative thread you referred me to, is NOT TO CHARGE THE TWO PACKS ON ONE COMMON LOOP. So yes, I quite now understaand I need one switch and batterycircut totally open/disconnected, practically as if I had another seperate kill switch on the on/off switch!

strato911

Randall,

Stephen (sfaust) seems to know what he's talking about. Past posts of his have shown he knows his stuff.

However, in the end, it's up to you. Conductivity tests on a switch are easy to perform.

rustyrivet

My Feedback: (6)

Easy for you to say. -A guy who splices microprocessors with a Microsoft edged Guillotine for the fun of it!

strato911

Actually, I am a computer technician, with an engineering background. I thought it was an appropriate avatar.

sfaust

My Feedback: (11)

Here is a photo of the Futaba switch. It shows the black lead indeed bypasses the switch, and would allow a common ground if two of these were used.

sfaust

My Feedback: (11)

Here is the JR switch. Even the negative leads go to posts on the switch, and are switched open or closed.

sfaust

My Feedback: (11)

The best thing you can do is to bench test your switches. Plug each switch into the receiver as you would normally. However, leave the batteries disconnected, so that you can use the connectors to put a meter on each black lead. Then test to see if you get continuity. If you do, you have a common ground, and need to either charge them separately, or unplug the battery from one switch if you want to charge them at the same time.

If you don't get continuity, then you're all set.

And if anyone wants to send me some old switches, I'll tear them apart, take photos, and post them with the other switches on my web site. Here is what I did on the comparison between the JR Charge Switch and the Futaba Standard switch. I wanted to know what the extra money was going for

http://www.giantscalerc.com/technical-switches.htm

rustyrivet

My Feedback: (6)

Thank you Gentlemen,

Gosh, only on the internet can one find a disection and full thesis about an on/off switch!!

Very interesting though Stephen, as the particular manner with which how the ground wire is strung on each of these switches, likely has direct bearing on the question I have raised. It's nice to know the internal construction of this simple but never the less, vital component of our rc system.

As far as anyone else requesting input, or furthering your study of switches by submitting one to you for examination, I wouldn't count on it. I think, you me and Dennis are the only ones out here in this purgatory. Those igneramuses! All the fun they're missing out on! I mean is this thread where all the action is or what!

All kidding aside, I'll invesitigate this matter in my lab...errr...I mean garage tomorrow if I get the chance betweeen work. Thanks. Appreciate the fussin. -Randall
PS Sorry to keep everone up past their bedtime.

strato911

If you think this is a strange topic, I read a book once titiled "How to Sh*t in the Woods" (non censored spelling). Very humerous, and insightfull reading for those who spend considerable time camping / canoeing / kayaking or similar activities communing with nature.

http://www.epinions.com/content_58615959172

AS for the late hour... I typically don't hit the sack before 1:00 AM.

sfaust

My Feedback: (11)

Based on the hits I get on my web page for the switches, I would say there is a much larger group that has a passing interest in the quality of the switches they put in their airplanes.

Its one of those things that if people have a way to get a quick and easy answer, they will go click once or twice to read the answers someone else has provided. However, they wouldn't take the time to disassemble a switch to find out for themselves.

I did it on a lark because I wanted to know what I am risking my high dollar airplanes to. $25 for a quick foray into switch design was cheap. I've had one offer for a switch already, so I'll revamp my web page to make room for another couple switches.

What compulsive people we can be at times when it comes to our hobbies

Oh yea, I might need that book above. Flying season is coming up and many fields don't have facilities