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Lipo for JR transmitter

Old 08-13-2008, 03:34 AM
  #1  
vonveska
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Default Lipo for JR transmitter

Hi,
I saw lipos for JR transmitters. But the lipos have 11.1 V and the NiCds have 9.6 V. Do you think it's OK to use the higher voltage batteries without damaging the Tx? Advantage of lipos is that they do not have memory effect so you can charge them any time.
Thanks for your advice.
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Old 08-13-2008, 05:22 AM
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rcflyair
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Default tx lipos

I used an 11.1v lipo in my Futaba 8UAPS for years without any trouble. The higher voltage will affect the voltage regulator in the transmitter, and since it has to handle an additional 1.5 volts, it will generate a bit more heat.

I'm sure it will work ok, but the real question is: Has the tx been designed to take 11.1v for long periods of time without shortening its lifetime? Will the additional heat degrade the electronics?

I would check with JR and see what they say. Also Common Sense RC markets the tx lipo packs and you might check with them....

Oh yes, one more thing. If your tx has a low voltage alarm, it won't be accurate with lipos. You'll want to monitor the battery voltage yourself, and charge it before it drops below 9v!!!
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Old 08-13-2008, 08:26 AM
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vonveska
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Thanks rcflyair for your reply,

I bought the battery already (I am waiting for delivery) so I will use it and I'll try to find out if there is any voltage regulator available. It would solve the problem. The heat is a bit worry, because even now I can feel the heat from the back of the transmitter using 9.6 V nicads. If it's too bad I'll go back to the nicads.
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Old 08-13-2008, 01:48 PM
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Morning,

I emailed JR last night and asked them about transmitter lipos: Will it work? Will it work, but degrade the lifespan? Will it affect the warranty? Their automated email response said we'd get an answer in 3-5 days.

Here's a trick as an alternative from a voltage regulator - simpler and cheaper. Wire two diodes in series between the lipo and the tx. 1N4001's (Digikey 1N4001GOS-ND) are rated for 1A at 50V and would work well. Each diode will drop about 0.7V, so the transmitter will see approx. 1.4 volts less than the current battery voltage. Since the tx already has a voltage regulator, you won't have to go to all the trouble and expense of duplicating it.

The only thing with the diode trick is you'll need to wire things so you don't try to charge thru the diodes (won't work). If you're charging thru the balancing connector, that would be perfect.

I'll post if and when I get an answer from JR.
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Old 08-13-2008, 02:38 PM
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everydayflyer
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A few points.

Charged voltage for a 8C Ni is approx. 11.6 volts and in a DX7 it drops to approx. 11.3 as soon as Trans. is powered up.

A charged 3S LiPoly will be approx. 12.45 after charging and will stay at >12 under load.

DX Transmitter's RF section works at 3.3V and they use a Linear regulator which in fact runs hot and waste a lot of energy (mAh) . Some have replace the regulator with a switcher type and it elinates all of these problems.

I use Ray-O-Vac Hybrids NiMH 200 mAh AAs in my DX7. I fly most everyday and average about 10 hours per week. I charge my DX7 with the supplied Wal charger every 7 to 10 dyas and have never had it to go to low voltage alarm except when I was testing it by leaving it on for over 12 hours continious..

The preminum high capacity low self discharge AA cells are Sanyo Eneloops and there are several vendors who will build a Trans . pack from these for the non DIY type. Plenty of run time, will not go dead setting for months and much simplier / safer than LiPolys.

I checked the timer on my DX7 and during the past 8 months I have 58 hours of transmitter on time with just my 3DHD Extra 300 SHP. I also use the same Trans. with my EF Yak-54E, My MUS (44 hours) a Zero Gravity Pitts Phytoon and my Ascent glider.




Charles
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Old 08-13-2008, 06:17 PM
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sgf323
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I've been running a LIPO in my Spektrum for months at it works perfect. I also modded the voltage regulator so that the battery would last even longer.
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Old 08-13-2008, 06:43 PM
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Hey sgf323,
Did you replace the voltage regulator in your tx with a switching regulator?
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Old 08-13-2008, 06:46 PM
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Ok guys, here's from the Spektrum website.....


--------------------------------------------
Heads Up, Use the right batteries in your Spektrum transmitter for best results
Monday, March 17, 2008

Warning concerning use of non-standard transmitter batteries
Spektrum transmitters are designed to be operated on 9.6 or 4.8 volt Ni-cad or NiMh batteries only. Use of Li-Po or other power devices operating at higher voltage can add heat to the system, possibly overloading the power regulating transistor for reduced output. Despite what aftermarket battery manufacturers might suggest, use of non-standard batteries offers decreased reliability of your Spektrum. Our service department has received failures associated with Li-Po packs.
For increased flight time, please use increased capacity NiMh cells, like the JRPB5011 2500 Sanyo pack. Charge these packs with the JRPC223 9.6 volt 270mAh output charger.
--------------------------------------------------------------

Looks like everydayflyer called it.

Here's the link to the info.
http://www.spektrumrc.com/Articles/H...t=DSMChallenge


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Old 08-13-2008, 06:59 PM
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Figure.N9ne
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i use a 3 cell lipo in my dx7 and havent had any problems, a few other friends do too and we've been fine. thats not to say its 100% safe though.
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Old 08-13-2008, 07:06 PM
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Yes, I followed this write up: http://www.dimensionengineering.com/...ektrum_mod.htm

More info here: http://www.rcgroups.com/forums/showthread.php?t=548325

The mod was very easy. I simply used a dremel to cut the legs of the existing regulator, soldered wires to the remaining legs still on the board and routed the new regulator to a new location and hot glued it in place.
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Old 08-13-2008, 07:13 PM
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Thanks sgf323, that is excellent info.

I'm a little disturbed that JR/Spektrum (and probably everyone else) designed their power supply (voltage reg.) that way. A switching regulator is WAY more efficient. Oh, well, I guess its cheaper.

I'm flying the DX6i now, and it uses four Nimh batteries, which makes way more sense......
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Old 08-13-2008, 07:48 PM
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Another cheap part in the DX6 are the buttons at the bottom for Scroll/Channel, Increase/Decrease. After a while they just stopped working. I replaced the buttons on the board with similar ones from Radio Shack. It all went back together like stock so you can't tell, but it sure works much more reliably!
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Old 08-14-2008, 02:40 AM
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vonveska
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Thank you all for your excellent posts and help. I have a JR PCM9X II and I think all you have said here applies for this Tx as well as for the Spectrum etc.
I am surprised how long your batteries last (everydayflyer), I have to charge Tx after approx. 5 hrs flying time, I use 2200 mAh NiMh (Panasonic) and charge them either with Hyperion 606i or iMAX B6. Most of the heat comes from the RF module.
I like the idea of using the diodes to drop the voltage - I'll try it (thanks rcflyair), well if I decide to use the lipos. I crashed one model already, when the Tx batt. alarm went off and I was reluctant to leave the sky when the lift was so great ... The Tx went blank when I was about 5 m high approaching the landing area.
There is one more thing I'd like to mention - the discharge of Tx batteries. If I want to discharge the batt. I have to remove them from the transmitter and put them on the charger. If I leave them in the Tx and plug the charger in the Tx through the plug provided, the discharge does not work.
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Old 08-14-2008, 04:09 AM
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rcflyair
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The transmitter has a diode to protect itself from a charger being hooked up with reverse polarity. The diode will block the discharge.

The best choice is the Dimension Engineering switching regulator. Eliminates heat and increased efficiency (longer time between charges).

Let us know how it works out.....
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Old 08-14-2008, 02:09 PM
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mickey t
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Hi guys,
lets look at it this way. A TX originally didn't have rechargeable batteries, but it had AA alkaline batteries. Correct me if I'm wrong but, don't 8 AA alkaline's add up to 12V? There is no problem running a lipo in your TX, or the battery companies wouldn't be selling them. Just my 2c worth.

MT
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Old 08-14-2008, 04:26 PM
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1.2 x 8 = 9.6v
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Old 08-14-2008, 05:20 PM
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Yeah, brand new fresh alkalines start out at 1.5v per cell. Depending on the current draw (load), the voltage will drop off fairly quickly. So with a 500mA load from the tx, they would be down closer to 1.2v in the first hour or so. Alkalines have a sloped discharge curve vs. a more flat curve for NiMH or NiCad's. The more you use them, the lower the voltage gets. To make things easier for calculations, we use the nominal voltage (or that's about what the voltage is most of the time).

The question isn't really if the tx will work at 12 volts and up, rather will the additional heat shorten the life of the electronics.......
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Old 08-15-2008, 01:06 AM
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mickey t
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Originally Posted by rcflyair View Post
The question isn't really if the tx will work at 12 volts and up, rather will the additional heat shorten the life of the electronics.......
I don't think it's a problem, I have been using a lipo in my TX for the last 18 months and seen no problems.

MT
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Old 08-16-2008, 01:32 AM
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vonveska
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I ordered a switching regulator from Dimension Engineering - they shipped it next day after ordering (P+H only $1.25 to Australia), good stuff.
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Old 08-26-2008, 05:53 AM
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Default Lipo Tx - update

Probably nothing new for most of you guys, just an update:
I received my lipo yesterday and installed it in the Tx. The voltage was 11.8V, I left the Tx for 4 hours switched on. The heat was about the same as using NiCds and after 4 hours the lipos showed 11.3V.
A very good result for me. I don't think I will need another regulator. However, I will have to watch voltage rather then bar indicator on the Tx while flying.
Thanks for our help.
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Old 08-31-2008, 04:49 AM
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Originally Posted by everydayflyer View Post

I use Ray-O-Vac Hybrids NiMH 200 mAh AAs in my DX7.
Charles
Charles -- how do you connect those AA's to the plug-in in your DX7? Is there a battery holder a la the "old fashioned" ones like I used to have in my old Airtronics 3-channel car tx?

Thanks,

Ben
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Old 08-31-2008, 06:13 AM
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Ah -- think I found it -- are you using this?

http://www.jrradios.com/Products/Def...ProdID=JRPB971


And can I charge the Rayovacs with this charger?

http://www.keithscameras.com/servlet...Compact/Detail

(I already have one... )
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