DIY $8 Lithium Transmitter Battery - Futaba FX18 ?

If you've been building electronic bits or modifying stuff you've bought then tell us all about it here. A good place to discuss the installation of 2.4GHz DIY modules too.

Re: DIY $8 Lithium Transmitter Battery - Futaba FX18 ?

Postby RCModelReviews » Tue Jun 15, 2010 3:24 am

JR expressly state that using a 3S lipo will invalidate their warranty, Futaba don't but it's still not such a good idea, especially when running 2.4GHz.

Most radios will tolerate a 3S lipo okay but some will inevitably fail due to overheated regulators.

Putting a couple of diodes in series with a 3S lipo will drop the voltage by about 1.2-1.4V to a maximum of about 11V when fully charged and around 10V for much of the charge -- which is within most manufacturers' specifications.

However, lipos are not without their other issues -- such as the ever-present fire danger and the worry that if you leave your radio on unintentionally and the battery goes flat -- it's probably going to be stuffed.

That's why I opted for the protected cells -- they're not likely to go bang through overcharging (they just disconnect themselves) and you can't over-discharge them because again, they disconnect themselves when they reach the minimum safe operating voltage.
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Re: DIY $8 Lithium Transmitter Battery - Futaba FX18 ?

Postby FBURDEN » Tue Jun 15, 2010 5:14 pm

Bruce, re. Lithium Protected Cells, is it ok to charge these with the HobbyKing Accucell 6 chargers? I read somewhere, or thought I did, that one shouldn't put protected cells in these chargers, but I could be wrong...


Thanks for all the info. Great Website by the way!!!!
Can't wait to read your review Turnigy 9X, latest version!!!
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Re: DIY $8 Lithium Transmitter Battery - Futaba FX18 ?

Postby FBURDEN » Tue Jun 15, 2010 6:36 pm

HK Accucel 8 Documentation:
"Do not connect more than one battery pack to the charge lead at any one time.
Do not attempt to charge or discharge the following types of battery."

"Battery pack, which consists of different types of cell (including different
manufacturers).
-Battery, which is already fully charged or just slightly discharged.
-Non-rechargeable batteries(Explosion hazard).
-Batteries that require a different charge technique from NiCd, NiMH, Lilo,
LiPo, LiFe or Pb.
-Faulty or damaged battery.
-Battery fitted with an integral charge circuit or a protection circuit.
"
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Re: DIY $8 Lithium Transmitter Battery - Futaba FX18 ?

Postby RCModelReviews » Tue Jun 15, 2010 9:46 pm

Well I charge my protected cells with an iMax B6 charger and it works just fine. I'm not familiar with the Accucel charger but I'll see what I can find out.

So long as you don't try to over-charge them (by using too much voltage) then the protection circuitry on the cells doesn't kick at all -- although it pays to use the LiPo setting (4.2V per cell max) rather than the Li-Ion setting (4.1V per cell max) because there is a small voltage drop across the protection circuit.

And the 9XV2 arrived late yesterday so I'll be working on the review today.
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Re: DIY $8 Lithium Transmitter Battery - Futaba FX18 ?

Postby jomarx » Tue Jun 15, 2010 11:57 pm

AFAIK, the HobbyKing Turnigy Accucel6 is more or so the same as the iMax B5...
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Re: DIY $8 Lithium Transmitter Battery - Futaba FX18 ?

Postby FBURDEN » Wed Jun 16, 2010 12:12 am

yep, going to order one very shortly...
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Re: DIY $8 Lithium Transmitter Battery - Futaba FX18 ?

Postby TG72 » Mon Nov 08, 2010 5:00 pm

Hello All :!: , I just did a 2 cell trustfire battery conversion for my JR XP-6102 after hacking with the FrSky hack module. :o I would like to foil the tx low voltage alarm with an 8.2K resistor rather than cut out the alarm altogether. I was wondering if anyone has done this with a similar JR transmitter and might have any pictures to post for an electronics novice like me :oops: . I saw Bruce install a Corona Diy on a JR X-378, but he didn't elaborate on whether he made the low voltage modification like he did on the Turnigy 9X. I'd also hope to perform the same mod on an older Futaba T6XA if there any pictures on that also. This is a great forum with a great bunch of guys. I would have never been able to do a lot of this without your much needed help. Thanks again, Tom
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Re: DIY $8 Lithium Transmitter Battery - Futaba FX18 ?

Postby RCModelReviews » Tue Nov 09, 2010 9:27 am

The problem with doing the $8 battery mod on other transmitters is that most manufacturers (unlike FlySky) guard their schematics as if they were gold. That means it's a very difficult task to work out where the relevant resistors are located.

I didn't modify the JR radio I converted to Corona -- I just left it on 9.6V.
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Re: DIY $8 Lithium Transmitter Battery - Futaba FX18 ?

Postby TG72 » Tue Nov 09, 2010 12:31 pm

RCModelReviews wrote:The problem with doing the $8 battery mod on other transmitters is that most manufacturers (unlike FlySky) guard their schematics as if they were gold. That means it's a very difficult task to work out where the relevant resistors are located.

I didn't modify the JR radio I converted to Corona -- I just left it on 9.6V.

Thanks Bruce! I guess as a last resort, I'll just cut the alarm wire and use a cheap clip on timer.
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Re: DIY $8 Lithium Transmitter Battery - Futaba FX18 ?

Postby Sugna » Sat Jul 02, 2011 1:32 am

Hi
I am think of doing the $8 battery mod to my 9x and I was about to buy the batteries but I heard some batteries aren't as good. :shock:
Can you guy tell me which "brand" of Li-ion is a good, reliable batteries for the 9x radio?

Thank you :D
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