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Old 02-03-2013, 06:47 PM   #1
B17man
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Build Review Ubecs and multiple Servos

Hi there peeps,

I am new to this Forum and looks like it will be coming in handy

I am busy building a large scale B17 Aircraft that takes 4x .52 nitro engines and what im planning on doing is making the servos and receiver run off of a Lipo battery, im telling people in advance that im a real noob when it comes to electronics lol so a little explanation will come in VERY handy lol

my plane has 9 servos in which will be digital and im planning on running 2 3000mah batts with 2 UBECS, im just not sure of all this amps and ohms stuff lol and how could i join these 2 bats to run as one.

Any Advice will be GREATLY appreciated hehe
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Old 02-03-2013, 08:07 PM   #2
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Why don't you just use one of these I use the smaller mah size ones for my planes love em. You will have no need to add a UBEC to the system.
http://www.atlantahobby.com/Store/pc...dproduct=14468
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Old 02-03-2013, 08:32 PM   #3
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The Life batteries would be the easiest and simplest way to go.
The voltage output is lower than Lipo, 2 Life batteries in series give you 6.6 volts, no need for a UBEC.

2100 mah would probably be enough, but if you want to parallel 2 of them to give 4200 just make a plug lead or buy one, that connects the red wires + from each battery together, and connects the black wires -- from each together, now you draw power from both batteries. DO NOT SHORT THEM OUT that equals FIRE

I don't think even the IMAC planes use a 6000 mah battery pack, and I have counted 13 large super fast digital servos in them.

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Old 02-03-2013, 08:46 PM   #4
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If you do not mind explaining how I would set it up with 9 digital servos, and a receiver I would glady appreciate it, and would this battery manage 9 servos?

Regards
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Old 02-03-2013, 09:07 PM   #5
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Just plug the battery into a free spot on the RX and your good to go. I use a smaller LiFe battery running 4 servo's they are not digital. I do 3 flights and only put back about 75 mah into it this is only a 1300 mah rx battery.
That battery should handle nine servos it is not like your going to be asking a lot of these servos flying a scale bomber.

I also have the LiFe setup so after I pull my main battery pack I just shut it off same as a wet fuel plane.
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Old 02-04-2013, 01:05 AM   #6
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Originally Posted by B17man View Post
Hi there peeps,

I am new to this Forum and looks like it will be coming in handy

I am busy building a large scale B17 Aircraft that takes 4x .52 nitro engines and what im planning on doing is making the servos and receiver run off of a Lipo battery, im telling people in advance that im a real noob when it comes to electronics lol so a little explanation will come in VERY handy lol

my plane has 9 servos in which will be digital and im planning on running 2 3000mah batts with 2 UBECS, im just not sure of all this amps and ohms stuff lol and how could i join these 2 bats to run as one.

Any Advice will be GREATLY appreciated hehe
Yeah
A two cell LiFe battery is a direct drop in to replace a five cell Nickel Hydride battery. These LiFe batteries do not require a voltage regulator, as compared to the LiPo batteries. The voltage discharge curves for the 5 cell Nih and the two cell LiFe batteries is nearly identical. If you are after dual batteries, the LiFe and A123 batteries can be connected directly in parallel without any issues. That is not true of the Nicad or Nih battery packs.

But, in high discharge circuits, like your 9 servos, there is no comparison between a good LiFe battery and your "AA" sized Nih battery. These LiFe batteries can easily put out 10 Amps, where those Nih batteries can not.

Most of my club members flying the larger gasser type models have gone to the LiFe batteries. They have been working very well.

In fact, two of my club members have gone exclusively to the 2300 Mah A123 battery packs. These two guys are flying $$$$ wet turbine models, and absolutely will not go back to either the Nicad or Nih battery technology. The LiFe and A123 cells are charged with the same setting on a quality charger. Both have the same voltage characteristics.

Those A123 battery packs are capable of perhaps 5 times higher momentary current output compared to a LiFe battery. We had a model crash last summer in SE Wisconsin where a $$$$ model with a big gasser up front had one of the high power aileron servos dead short out. The receiver battery was a two cell A123 pack. That pack burned all the insulation right down to bare copper of the wires leading to that servo, before it finally went dead.

These A123 cells have metal jackets on them, and their internal wiring is solid copper. (Don't ask how I know )

These LiFe and A123 batteries absolutely must be charged on a balancing charger though. They can be charged at pretty high rates. The A123's can be charged from full discharge to full charge in less than 20 minutes with a high powered charger.

I've got over 100 A123 cells in my various models, for electric motor power. Typical currents pulled out of them is on the order of 35 Amps per cell. And, they last a very long time.

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Old 02-04-2013, 01:33 AM   #7
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Denny I was hoping you would drop in your the one who turned me onto the LiFe for my RX, and I am happy I did.
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Old 02-04-2013, 04:20 AM   #8
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Originally Posted by gramps2161 View Post
Denny I was hoping you would drop in your the one who turned me onto the LiFe for my RX, and I am happy I did.
Thanks
Everyone in my club that has gone to the LiFe or A123's for receiver power has been very happy, and are trying to convert the rest of the club members to do the same.

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Old 02-04-2013, 10:14 PM   #9
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www.scriptasylum.com - BEC calculator
Why is it the more batteries I use, the less servos the BEC can handle?
Digital servos and BECs!!!
rcadvisor.com/model-aircraft-bec-guide

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Old 02-04-2013, 10:27 PM   #10
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I see so i see that those liFe batteries are much better and i think im going to be ordering me some soon hehe these look like the new way of flying! a new ERA hehe again ty for all your help this has put me to ease! and now i can finally get it all going

will send pics to show u all
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Old 02-05-2013, 12:50 AM   #11
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Originally Posted by B17man View Post
I see so i see that those liFe batteries are much better and i think im going to be ordering me some soon hehe these look like the new way of flying! a new ERA hehe again ty for all your help this has put me to ease! and now i can finally get it all going

will send pics to show u all

One more item on these LiFe and A123 cells. Their recharging characteristics is VERY efficient.

So what good is this? Say you have a 2200 Mah LiFe battery, and after charging it, you put on three flights. Now, with a LiFe charger that also shows how many milliampere hours you put back in, recharge the LiFe battery. Lets say those three flights took 750 Milliampere hours to recharge.

Since the recharging of these batteries is so efficient, that 750 Milliampere Hours will be within about 5% of what those three flights took out.

My personal limit on any of these receiver batteries is to NEVER NEVER take more than 50% of the battery capacity out during any days flying. Why, just because, one day you might do more acrobatics, fly faster, you name it. That 50% is reserve flying time.

Now since those three flights took 750 Mah, that's 250 Mah each, so with a 1000 Mah limit, you can get four flights. Since these LiFe batteries can easily be field charged, it's only a few minutes to top of your battery. As usual, your results can vary, you must do your own tests and derive your own safe flying limits.

If your charger does not have the capability to show milliampere hours put back into the battery, this alone would be reason enough to buy one that does.

DennyV
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Old 02-05-2013, 01:34 AM   #12
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Originally Posted by B17man View Post
I see so i see that those liFe batteries are much better and i think im going to be ordering me some soon hehe these look like the new way of flying! a new ERA hehe again ty for all your help this has put me to ease! and now i can finally get it all going

will send pics to show u all

Forgot to mention, I'd put together a thread in wattflyer on this very subject a bit over a year ago! What happened, is I caught a fellow club member flying a $4000 wet turbine model, with only a single "AA" type 5 cell 2800 Mah Nih battery for the receiver. That model had some 8 or 9 high current servos in it. He was danged lucky that he didn't loose the model. The peak current pulled by his servos was measured at over 14 Amps when all were moved at the same time. I put a 14 Amp load on his AA Nih battery, it dropped down to 3.5 volts DC in a fraction of a second.

He has since gone on to these LiFe batteries, that can easily handle these momentary 14 Amps plus currents.

http://www.wattflyer.com/forums/showthread.php?t=62916

DennyV
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