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Old Sep 27, 2008, 03:59 PM
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Joined Dec 2003
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Question
Spektrum DX7 - 2 batteries to receiver?

Can I connect two 4.8v batteries to a DX7 receiver to prolong flight time?

If so, how do I do it?

BTW, would using a 5cell 6 volt battery pack fry the servos? Do I need to use a voltage regulator? Will be using 5 standard servos that came with the set + 1 Hitec servo for retracts.
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Old Sep 27, 2008, 05:16 PM
GreeneAeroFlyers
kenkey's Avatar
Greeneville, TN
Joined Mar 2004
287 Posts
Most standard servos will handle 6v fine. Check the specs on your servos to be sure. You can plug in a second battery pack into any unused ch. the two packs should be of the same voltage and mah to prevent lesser pack from drawing down higher pack.

Ken
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Old Sep 27, 2008, 05:25 PM
Tye
Chacotoma, NM
Joined Jan 2004
749 Posts
I suggest very strongly that you use a 5 cell battery pack, or two for greater capacity. Too many people have gotten into trouble by just using 4.8 v. with the Spektrum system.
Plug the second set into an unused channel like Ken says, and use a seperate switch and charge jack to charge it.

... zak
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Old Sep 27, 2008, 06:42 PM
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Frisco, TX, USA
Joined Sep 2001
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http://www.horizonhobby.com/Products...odID=SPMAR9100

Another option...
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Old Sep 27, 2008, 08:10 PM
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United States, UT, Salt Lake City
Joined Oct 2007
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I will likely be admonished for this ---but-- I use one (count em ) one 1100 ma A123 pack on models up to 50 cc. that's a tiny ,under 3 ounce pack--with a total usefulness of 1000 MA.
However the delivery is virtually constant for the entire 1000ma- and most other packs can't do that . AND-- recharge in 10 minutes no cooling off period - just hit er with 4 amps on a balance charger whilst you refuel - . My JR/JR Sport servo all operate perfectly with these packs -and no regs used (or wanted).
PS never combine unlike voltage sources!!! no 4.8 and a 6 volt This wil create a nice burned up wiring.
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Old Sep 27, 2008, 08:44 PM
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ebill3's Avatar
United States, WA, Puyallup
Joined Oct 2004
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Quote:
Originally Posted by gpang788
Can I connect two 4.8v batteries to a DX7 receiver to prolong flight time?

If so, how do I do it?
If you want to use two RX packs, go here and scroll down in the left frame to 'Parallel Operation......'.

Bill
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Old Sep 28, 2008, 08:24 AM
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Nice article there Bill, just to clarify, so using 2 packs is better at prolonging flight time then using a 5 cell setup??

At the same time, 2 packs will also double the time taken for the batt voltages to drop to min levels?

Am a little confused now. Should I go for the double pack or the 5 cell option?
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Old Sep 28, 2008, 09:58 AM
GreeneAeroFlyers
kenkey's Avatar
Greeneville, TN
Joined Mar 2004
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On my larger planes I use 2 5cell packs with separate switch and charge jack for each. Besides longer flying time the 6v packs also slightly increase the servo speed and torque.

Ken
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Old Sep 28, 2008, 01:34 PM
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United States, WA, Puyallup
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Quote:
Originally Posted by gpang788
Nice article there Bill, just to clarify, so using 2 packs is better at prolonging flight time then using a 5 cell setup??

At the same time, 2 packs will also double the time taken for the batt voltages to drop to min levels?

Am a little confused now. Should I go for the double pack or the 5 cell option?
A bit of apples and oranges here. Using two packs in parallel will increase the capacity - the flight time. Using five cells increases the voltage, but not the capacity. Five cells will help insure no low voltage drop out, but not increase flight time.

If you want the insurance of no drop out, increased servo performance, and increased flight time, go two 5 cell packs in parallel.

Bill
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Old Sep 28, 2008, 10:35 PM
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In my Super Stearman bipe with 6 power hungry Spektrum DS-821 digital servos (4 of which in the wings for the ailerons) I installed 2 5-cell packs. Each connects to its ow switch harness. The two harnesses plug into the AR7000 receiver - one via a Y-harness to the BATT/BIND/DATA slot with a Voltwatch into the other end of the Y; the second switch harness via another Y-harness to the ELE channel with the elevator servo plugged into the other end of the Y. This provides battery and switch backup in addition to the increased power and duration capabilities of the battery system.

i.
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Old Sep 29, 2008, 09:10 AM
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United States, UT, Salt Lake City
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Quote:
Originally Posted by ivanc
In my Super Stearman bipe with 6 power hungry Spektrum DS-821 digital servos (4 of which in the wings for the ailerons) I installed 2 5-cell packs. Each connects to its ow switch harness. The two harnesses plug into the AR7000 receiver - one via a Y-harness to the BATT/BIND/DATA slot with a Voltwatch into the other end of the Y; the second switch harness via another Y-harness to the ELE channel with the elevator servo plugged into the other end of the Y. This provides battery and switch backup in addition to the increased power and duration capabilities of the battery system.

i.
A local friend -has a big Stearman-with a 5 cyl radial - scale - a real showstopper -
I set him up with 2 ,2300 ma A123 -packs- As he is a professional welder - he appreciates the "power" in this setup.
I use two puny looking A123 cells (1100ma) for my Bucker Jungman - a TOC 31% design I did years back. plenty of amps -just nor many amp hours.
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Old Sep 29, 2008, 12:04 PM
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Quote:
Originally Posted by ivanc
second switch harness via another Y-harness to the ELE channel with the elevator servo plugged into the other end of the Y.
Could I connect the 2nd pack to any other channel? What about a direct connection to a spare channel without going thru a servo?

Guess I might go with the 5 cell 2 pack setup but will this get too heavy?
(Plane in question is a world Models Aeropet 50. Intending to power it with a OS55ax)
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Old Sep 29, 2008, 12:41 PM
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overkill - one decent 1000ma setup - is fine.
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Old Sep 29, 2008, 12:57 PM
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ivanc's Avatar
United States, TX, Round Rock
Joined Dec 2004
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Rich is correct - a 2-pack setup for a 50-size plane is an overkill.

i.
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Old Sep 30, 2008, 10:36 AM
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hmm.. but I am still worried about the voltage level.

What do u guys think of lipos?

Am planning to get one of these to power my receiver:
http://shop.rotor.com.sg/show-detail...894B6B2B}&pn=1

Apparently, its for helis. Comes with a 2S1P 7.4V 1900mAh/12C Li-Polymer Battery.

Would lipos be better both in terms of voltage margin and prolonged flight time over nicads? Killing 2 birds with 1 stone?
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