Avalanche2

hey, can anyone tell me how to set up a 2 battery RX sytem... Its for an Aeroworks Edge 540t.. Ive got an extra channel on the RX but, Im not sure about the actual hook up... not even sure if it needed but after reading about batteries its a thought... thanks for the help

bruce88123

Use 2 battery packs and 2 switch harnesses. Charge each battery through it's respective switch harness. Plug switch harnesses into any 2 channels on the RX, typically the BATT and another unused channel. If all channels are used you can use a Y-harness (one side to servo and other to batt switch) but DO NOT connect both batteries to the same channel slot.

overbored77

My Feedback: (11)

Avalanche set both of them up as you would for a single battery (seperate switches etc) then plug one into the BATT channel
and the other into any unused channel. Using this system is good insurance. Please remember to check the CG of the palne after
adding the second RX pack.

Edit: Bruce types faster than I do

Avalanche2

thanks guys... are any of you using this set up? is it needed??? and my thumbs work better than my typers too...

alan0899

G'day Mate,
Yeah, I'm using this setup, & I may never need it, I have 2 packs both 4.8volts, 1 is 1700Mah the other is 1100Mah nicad, I also have an in plane indicator that tells me the lowest voltage that the receiver saw during a flight, & it has never gone below 4.8 volts, this is with a AR7000 RX.
But I'm pretty sure my RX voltage won't drop to an unacceptable level, so it stays.

j.duncker

My Feedback: (2)

I do not like dual battery systems. There is more to go wrong. Simplicate and add more lightness! Just pick the correct battery size to begin with and install a battery monitor if you are marginal or have doubts. I do this on my helis with digital servos because the current consumption is huge and variable depending on what kind of flying you are doing.

I would rather fast charge between flights than rely on seperate batteries. The model shops will advise 2 batt setups for obvious reasons.

TWO EXCEPTIONS

1 If you are using mechanical retracts then have a seperate battery that feeds the retract servo only. Eventually most people get a retract jam - stalled retract servo - very high drain during the flight.

2 If you have a split servo system with TWO rxs and the ability to fly the model on either RX then obviously having TWO batteries one per RX is a safety feature.

48 years of radio flying.

alan0899

G'day Mate,
I would rather have 2 switches & 2 batteries, so if one switch or battery failed, which can happen easily, most electrical failures are open circuits, not shorts, I have another backup switch & battery.
I am an electrician by trade, so I know about redundency, in the hospital, where I work, we have 2 high voltage power supplies, & an emergency generator as backup, plus UPS power supplies, so I use the same principle of redundancy, especially if it can save my plane.
Just my opinion, since I have lost planes recently. from failed batteries & switches, & that was before my DX7.

CGRetired

My Feedback: (1)

Interesting issue. What happened to me is probably the best reason to go with dual batteries (as setup explained by Overbored and Bruce) and after this incident, I added voltwatch to the setup which worked out very well.

What happened is this. My Venus II (pattern plane) has dual NiMH batteries, 6 volt packs, both 1200 mah. That's lots of available amps for this plane to fly just about all day... or so I thought.

After the third flight, the plane seemed to be acting somewhat sluggish, so I just decided to check both batteries to see how they were doing. The first battery read 6.3 vdc which was just fine, and the second battery read.... hmmmm.... didn't read anything. The display on my Dubro voltmeter showed a flashing display then nothing. Hmmm what's wrong here.

So, I borrowed someone else's voltmeter and checked it thinking that perhaps my voltmeter was going bad or something. Same reading. Flashed the LED's then nothing.

I started to get a tad concerned so I called the "club pro" over.. he just happened to be around that day.. and he checked it both in the plane then we removed the wings and removed the batteries (both of them) and checked them both again. One read 6.3 under load the other.. well, flashing LED's and then nothing. WOW! A bad battery!! And it was only a few weeks old.

Fortunately, I had a spare, so I put that in, put both on the field charger and let them recharge.

The charger jack is disconnected when the switch is turned on so the VM only works with the switch off. But, we decided that the bad battery (which I checked after I charged it on the way to the field that morning) had failed during flight and the good battery had taken over the load.. and was also trying to charge the bad battery. So, had I just checked one battery thinking that both would be the same, I would have added some fuel to that fire and had a serious problem.

Moral to this story is, yes, dual batteries are a great idea and frequent checking of batteries is even a better idea.. or a great way to insure that your setup, either single or dual, is working properly.

I just have to think about this a bit and consider what would have happened if I had a single battery setup in that plane, and that battery failed in flight. Ah my nice Venus would be history now.

Oh, by the way, the voltwatch is always connected to a vacant channel (I had one more left..ha..) and monitors both batteries. You just have to learn the trends of discharge during operation to realize what is going on. Of course, you cannot see the voltwatch during flight, but before and after, you certainly can. I usually start the plane, make engine adjustments, check controls (make sure the ailerons are not reversed for instance), then I turn off one battery switch and watch the voltwatch... if ok, I turn it back on and turn the other one off and check the voltwatch. If all is ok, I turn it back on so both are on, then play with the controls and watch the voltwatch. You can detect binds in controls, end stops for throttle, and so on. Cheap insurance.

Sorry for going on and on, but I feel this is an important issue and thought it worthwhile to add my 2 cents worth.
DS.

bruce88123

From what I read a lot of guys are starting to use dual 6 volt packs on larger DX7 planes with high servo loads. This is to avoid the RX reboot problem they appear to be experiencing.

CGRetired

My Feedback: (1)

RX reboot problem?

Please explain, Bruce.

I use DX7 and the only thing I've seen is one time the TX display came up reversed (like looking in a mirror). Cycle the TX and it went away. I've never heard of this RX reboot problem.

Thanks.

Dick.

bruce88123

Read about it in the radio forums. Under heavy loads, especially spikes, the battery voltages can go too low and the RX's reboot. During that brief period, no control.

http://www.rcuniverse.com/forum/m_4888165/tm.htm Long thread

CGRetired

My Feedback: (1)

Thanks, Bruce.

I will head on over to that forum and read up on this.

So far, I don't have heavy loads.. that I know of anyway. The Tiger 120 does have 7 servo's (two aileron, two flaps, elevator, rudder, throttle) but I don't use the flaps and there is no end-point bind there either nor is there one in the throttle, so it's pretty much a normal load and I use a 1500 mah NiMH RX battery.

Thanks again.

Dick.

CGRetired

My Feedback: (1)

Ok, Thanks, Bruce. I scanned through then focusing on the areas about this re-boot situation and it appears that low voltage and range seem a big factor in this situation. Of course, the fix is to maintain battery voltage above the point where it will cause problems. Dual battery setup's using larger than typical capacity batteries is a good way to avoid this problem. Again, within reason. But with that Tiger 120 with OS 1.20 AX engine.. and that pound of lead I needed in the nose to obtain a proper CG, weight is not an issue.. [:@]

So... a pair of 1200 mah NiMH batteries seems just the ticket.. and voltwatch.. loading voltmeter.. all those bells and whistles.. plus a little diligence and perhaps I won't see the problem.

Dick.

bruce88123

Yep, carry batteries - not lead.

Avalanche2

thats the smartest quote Ive heard in a long time. I really appreciate all of the input... It does seem to be rare that battery failure is the cause of most crashes but, it sure seems to be cheap insurance to double up. If it was just a plane we could pluck off the shelf and fly it may be different but, most like me (I think) pour a lot of themselves into making a plane they are proud of and to see it dig a hole for a lack of 25.00 and a tad more effort is just a shame. Thanks again all... this has to be one of the best web communities on the net.

bruce88123

It's not just the battery(cell) that goes bad. The tabs that connect the individual cells to make up a "pack" can break or otherwise fail, the wires can come loose, a connector can come loose, a switch can fail and more. Redundancy is there for a reason. Why do you think full scale planes have triple-redundant fail-passive systems?

opjose

One caveat:

Do not mix batteries of different ages or capacities as one poster above has done.

Make sure that they are the SAME capacity and that you charge them both at the same time and for the same duration.

You want the batteries to be equally charged?

Why?

Well the "stronger" battery will discharge itself into it's weaker pair.

This is one reason we have balance chargers for Lipos... to keep all of the cells in a pack equally charged.

With two RX batteries connected to the same common connectors, things are no different.


One bad cell on one battery will adversely affect the lifespan and output of the other good battery as well.

That is why the "big boys" use special circuitry to switch from one battery pack to another when something happens to a pack. Effectively each pack is isolated from the other...

What you are describing does not do this.

alan0899

G'day Mate,
You could not be further from the truth, see here, http://www.rcbatteryclinic.com/
There is no problem mixing pack capacities, but must NEVER use packs of different VOLTAGES, as well as NEVER charge the 2 packs in parrallel, you must either charge one then the other or use 2 chargers.

opjose

No

His web page lists NiCD's only...


See:

http://www.supreme-brands.co.uk/usef...e-faq.htm#no15
http://data.energizer.com/PDFs/Rechargeable_FAQ.pdf
http://ask.metafilter.com/30954/Can-...nt-mAh-ratings
http://www.alltekpower.com/faq/index.asp?a=4&q=28

alan0899

G'day Mate,
Sorry, but you are still wrong, the web sites you quoted, were taking about replacing CELLS of different capacities, in a pack. I am talking about using 2 separate packs of the same voltage, same chemistry, & possibly different capacity, with 2 separate switches, & 2 separate charging leads in the same plane.
There are no problems when doing this.

CGRetired

My Feedback: (1)

If you talk to the "pro's", the guys that are real serious about their RC hobby.. and I know several Pattern type pilots that are just this way, adding some sort of switching unit now becomes one more potential point of failure.

Their answer to this is simplicity. Two batteries, each into a separate RX slot and a separate switch for each battery. Period. For a normal setup, if you are not using separate channels for dual-aileron servo's (using a Y connector into channel 2 (airtronics) for instance), you will need a 7 channel RX to do all this. Four channels dedicated for normal functions, throttle, aileron, rudder, elevator. Then the remaining three for power.. two battery connections and if you use one (highly recommended), one for a voltwatch type device.

Again, the more you add, the more points of failure you add. But, there is a big difference between redundancy and gadgets.

The key is to keep it simple, yet make sure you are adequately protected... within reason. Add more and you add more weight and potential problem areas... more stuff to check out, and so on.

Remember the KISS principal.. Keep It Simple Stupid (not pointing at anyone, by the way, it's just a saying so please don't get offended. If you do, then please... get a life.. if not.. then you understand what I am trying to say).

DS.

exeter_acres

My Feedback: (2)

Do you fly giant scale?? (ie 35% or more)
Do you use a single battery in Giant scale planes?

opjose

No sorry, you didn't get it then...

A cell is a cell...weather or not it is in the same pack or a differnt pack... it matters not. They are all electrically equivalent thanks to the common connections...

e.g. once you plug in TWO batteries into one RX their poles are common to each other, and it's the SAME as if you have CELLS of different capacities in parallel!!!

No difference to the above what-so-ever...


The references I gave you all apply... you can turn up hundreds of others with a simple google search as well... yet only his assertion to the contrary, which he acknowleges - IS - problematic, but " not overly so " when it applies to NiCDs...

... and the battery clinic did not deal with the issues of overdischarging the battery with the smaller capacity that this will cause too if you are not extra careful, since now you have to be more on top of things...

Move to other chemistries and the warnings against this become much more dire.

alan0899

G'day Mate,
I'm not going to argue, I am using the method of 2 batteries & 2 switches, but different capacities, NO problems at all, there would be a problem if I used different voltages, the higher voltage pack would try to charge the lower voltage pack, but the thing to remember here, is that you should never let a battery pack or packs, discharge to a low level, we MUST keep a watchful eye on them, no matter what we have, & the fact that with this method, we now have 2 current paths to the RX, so if an open circuit happens in a switch or battery pack, we have REDUNDANCY.
And that is useful in any plane, whether it is 2.4Ghz, or any other radio frequency.
The bottom line is, the RX MUST have a good power supply, or the plane in question will meet an untimely end.
And it matters not, how we achieve that power supply.
I hope everyone has a great weekend of flying.
Safe flying is no accident.

j.duncker

My Feedback: (2)

In response to Exeter acres.

I do not fly giant scale but I do fly a wide variety of models from ultra light indoor stuff, through 12th scale combat, club 2000 pylon racers, 3D profiles, 1/4 scale bipes and a high speed Gas Turbine scale model.

I fly a lot, my own models, other peoples on buddy box set ups [ I am an instructor at my local club] and am often asked to test fly models after checking them over.

I am an old fart who has been flying RC since the days you built your own RC equipement.

I agree with you if it was something like a 15 foot span B17 then it makes sense to use 2 RXs with separate batteries and drive multiple surfaces with sufficient redundancy to get the model back on the ground if one system fails. However the original post relates to An Edge 540
If this was mine I would use a single battery single switch set up. I fly Futaba and would be happy using an unregulated 5 cell 6volt NiMh pack of 1800 mah capacity and would expect to use substantially less than 200 mah per flight in the above model even with an all digital set up.