DIY $8 Lithium Transmitter Battery - Futaba FX18 ?

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DIY $8 Lithium Transmitter Battery - Futaba FX18 ?

Postby dufan_98 » Tue Jun 08, 2010 9:09 pm

Dear readers!

I really like this idea! Anyone who did this projct on his Futaba FX18?
The problem for me is, how to find out where/how to fool this transmitter about the different voltage.
Is it also just a resistor?
Where is the right place in the FX18 to install it?
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Re: DIY $8 Lithium Transmitter Battery - Futaba FX18 ?

Postby RCModelReviews » Tue Jun 08, 2010 10:12 pm

The only problem is that all radios use different methods for measuring the transmitter battery voltage. If I had a Futaba FX18 sitting here it would likely be a relatively simple task but without one I have no idea what components would need to be changed.
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Re: DIY $8 Lithium Transmitter Battery - Futaba 2.4Gig 6EX ?

Postby FBURDEN » Wed Jun 09, 2010 5:19 pm

Hi, Great Website and Reviews by the way!!


Hey, I'm thinking about buying those $8.00 Lithium batteries. 2 packs of 2 so I can solder together 3 so I can replace the nicad 9.6 vold, 600 mah that comes with it. Just the battery, no electric mods.

3*3.7 is 11.1volts which I'm guessing should be ok for this transmitter.

Think that will work?

Greetings from Vancouver Canada!!

Looking forward to your review of the new Turnigy 9x errrrr... 8x V2!!!
FB
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Re: DIY $8 Lithium Transmitter Battery - Futaba FX18 ?

Postby FBURDEN » Wed Jun 09, 2010 11:23 pm

Oops I just realized that those Lithium batteries are bigger than AA batteries... humphhhh!! Not sure how that will fit in my 6EX without butchering the plastic cover. Maybe I'll have to stick with the Hobbyking nimh, get 8 of them and solder them together? How tricky is it to solder these things together?
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Re: DIY $8 Lithium Transmitter Battery - Futaba FX18 ?

Postby RCModelReviews » Wed Jun 09, 2010 11:39 pm

Soldering the AA cells is pretty easy but you have to avoid using too much heat.

Here's how I do it.

1. make sure you have a soldering iron that's hot enough (40W is about right)

2. use some wet-and-dry sandpaper to clean up the ends of the cells (get rid of tarnish)

3. apply a hot iron to the end of the cell and feed solder onto the cell, right next to the iron (not onto the iron itself). The solder should melt and flow within a second or so. Don't hold the iron on for more than 3 seconds or so.

After you remove the iron, blow on the end of the cell to cool it as quickly as possible.

If the solder balls-up and doesn't flow then clean the end of the cell again and make sure you've got all the tarnish off before trying again.

Lead-free solder is crap -- use regular flux-cored lead/tin solder for this job, it works much better.

4. repeat step 3 until you've got a nice shiny puddle of solder on each end of all eight cells.

5. take the wire you're going to use to join the cells, cut into suitably sized lengths and strip about 1/4 inch (6mm) of the insulation away on each end.

6. using the hot soldering iron again, tin the ends of the wire so that they've got a good coating of solder. Again, when doing this, don't apply the solder to the iron, heat the wire and apply the solder to the wire -- it should wick-up the solder like string wicks up water.

7. attach the wires to your cells by placing the tinned end of the wire on top of the solder-puddle you've already made on the cell-end then apply the soldering iron on top so as to cause the heat to first melt the solder already on the wire and then the pool of solder on the cell. This is called "sweating" the wire onto the cell. This should take no more than 3-4 seconds. Remove the soldering iron and avoid moving the wire while the solder cools.

Repeat step 7 so as to get all your cells wired in series then connect the wires to the last + and -

8. Now make sure your batteries aren't going to move around -- you can use tape, heatshrink or the odd drop of CA to keep them together.

All done!

The key thing to note is:

Don't overheat the cells. Using a soldering iron that's too small or not cleaning the terminals properly are the main reasons why you might end up overheating the cells. The solder should melt very quickly after the iron has been in contact with the cell for a second or so.
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Re: DIY $8 Lithium Transmitter Battery - Futaba FX18 ?

Postby FBURDEN » Wed Jun 09, 2010 11:45 pm

Super Excellent!
Thanks!
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Re: DIY $8 Lithium Transmitter Battery - Futaba FX18 ?

Postby FBURDEN » Thu Jun 10, 2010 6:28 pm

What do you think of the following option:???
HobbyKing, just restocked the following - Turnigy 1450mAh 3S 11.1v Transmitter Lipoly Pack, which fits my transmitter.
(Great price at $7.95!!!!)
It has a Discharge rating of 1c. (is that safe enough? or do we need a put in a small fuse as well???)

I'm wondering about the idea several people suggested about soldering on 1 or 2 diodes to the above pack to drop the voltage a bit, for those of us who
are nervous about putting a freshly charged 12.5V!! pack in our Radios.
If I do that will, this battery now be as safe as nicd or nimh batterys? now that the voltage is lowered a touch???

******************************************************************************************************************************************************
Either that or I'm going to see if I can dremel a few grooves out of the lower part of the battery compartment, so that those Lithium batterys could fit in there nicely.... hmmmm... I also love soldering!! and those Lithium batteries are rated at 2400 mah... Nice!!!!!!

Thanks!!
Ford B.
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Re: DIY $8 Lithium Transmitter Battery - Futaba FX18 ?

Postby RCModelReviews » Thu Jun 10, 2010 9:46 pm

It depends a little on what RF module you're using as to whether the 3S lipo is a good idea.

Looking at the circuitry, the 9X board itself should take a 3S lipo without any problems but some RF modules with linear-regulators (like the Corona) will get pretty toasty inside.

The FrSky (and some other) modules have a switching regulator which is much better and they'll run cool.

The only problem(s) with a lipo battery is of course that if you leave your radio on accidentally and the battery becomes fully discharged -- it's stuffed.

Likewise, you should be *very* careful charging that battery and (as with all lipos) never leave it charging unsupervised due to the fire risk.

That's why I prefer the protected lithium-ion cell.s
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Re: DIY $8 Lithium Transmitter Battery - Futaba FX18 ?

Postby FBURDEN » Thu Jun 10, 2010 10:17 pm

Yep, I've got a Futaba 2.4 Gig 6EX. Futaba via my local Hobby Shop guy are totally against putting a lipo in it... no reason, just don't do it, "it could damage your radio".

So the $8 Lithium wins, now I'm printing off your Soldering Battery Instructions!!

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

Postby FBURDEN » Fri Jun 11, 2010 5:29 am

Very Rookie Question here?

If I solder 3 of these lithium batteries together how do I recharge them with the HK Accucell 6 or Accucell 8?

Besides the connection to the radio, what other connectors to I need to have to attach it to the Accucell? So that the 3 cells get properly balanced?

Thanks,
Ford
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