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Old Jun 17, 2002, 05:57 PM
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Joined Feb 2002
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Using Lithium Batteries for Receiver Pack

Folks,

I posted this in the sailplane forum, but the thread didn't get much traction. After reading through this forum, it seems the posting may be more appropriate here...

Here's the post...

I've got an Omega E Glider that I'm finally starting to get comfortable with. Recently, I had a flight that included a killer thermal on the last climbout. Came in for a landing and had the best landing to date with this plane.

When I got home, I was using the remainder of the charge in the battery to test some programming and found out that there was no "remainder" to the charge. I was incredibly lucky!

I'm now thinking of adding a receiver battery in addition to the battery for the motor. I've got a couple of 2 cell Lion batteries that are 750 MaH at 1.5 Oz (picked these up from Hobby-lobby for my Pico Stick - good long flights out of that and I've even had it in a thermal once). I Figure these should readily drive the 4 servos in the plane for something like a day and 1/2 :-).

What do I need to do to use these? Since the voltage out of the pack is something like 7.2 V, it would seem I need something to regulate the voltage to that required for the receiver. Is there something on the market that does this, or would it just be easier to get something like a speed controller (rated for 4 servos - any suggestions) and use that.

Any and all suggestions welcome!
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Old Jun 17, 2002, 06:28 PM
Master Crasher
sanjoh's Avatar
Sunrise, FL
Joined Nov 2001
162 Posts
I've been using li-ion in my giant scale stuff and just converted a tx over. You'll need a voltage regulator, I found the best deal at http://www.maxxprod.com/mpi-21.htm 6v for 19.95. 1500 li-ion would last a very long time. Next you'll be looking for larger tx batteries!
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Old Jun 17, 2002, 06:39 PM
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opualuan's Avatar
San Jose, CA
Joined Sep 2001
3,863 Posts
$20 seems a little steep... for $4 from radio shack you can get a 1A 5v regulator, they might have heavier duty ones there as well... or at other electronics shops...
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Old Jun 18, 2002, 03:43 PM
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Joined Feb 2002
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Sanjoh,

Quote:
Originally posted by sanjoh
I've been using li-ion in my giant scale stuff and just converted a tx over. You'll need a voltage regulator, I found the best deal at http://www.maxxprod.com/mpi-21.htm 6v for 19.95. 1500 li-ion would last a very long time. Next you'll be looking for larger tx batteries!
Thanks - that's the sort of thing I figured would be out there! Now that I know they exist (in a form other than just the raw voltage regulators), I'll see what options there are.

I may be looking for a 4.8V or 5V regulator as this would make the battery last longer and I'm not sure I really need the extra speed or torque on my servos.
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Old Jun 18, 2002, 06:25 PM
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United States, CO, Longmont
Joined Jul 2001
2,827 Posts
You might be interested to know that many receivers and servos run very well on 3.1 volts. This makes them a candidate for one cell with a nominal 3.6-3.7 volts. Consider puting your cells in parallel. I have only tested the Hitec 555 and FMA Extreme5. They are both flawless. The Extreme is even fully spec'd at 3.5 volts. I run my DLG glider with the Extreme, two HS-50's and a gyro on only one 830mah li-ion. It goes fro more than 5 hours.

Q
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Old Jun 24, 2002, 06:10 PM
Don't provoke my wife!
Fort Worth Texas
Joined May 2002
363 Posts
Quacker, so you think I could use one li-ion cell in my 2 meter sailplane using 2 micro servos and Hitech 555. What kind of charger do you have to use and how much are they.
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Old Jun 24, 2002, 06:19 PM
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Broomfield, CO, USA
Joined Jan 2001
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Regarding the regulator at http://www.maxxprod.com/mpi-21.htm, which makes it sound pretty slick about how it regulates down to 6v and then bypasses the regulator. This is actually a feature of most any linear vreg that you buy... once the voltage goes below that which it can regulate it just becomes a pass-through device. The trick is finding one that minimized the forward voltage drop.

I've seen Quacker's qualcomm powered DLG, very light with that single Qualcomm.
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Old Jun 24, 2002, 08:52 PM
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United States, CO, Longmont
Joined Jul 2001
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Ripley:

When servos are run at 3.6 volts, there is not much power available. For a DLG, that's fine. For a 2 meter, you need to judge carefully.

Q
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