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Cannot charge Futaba Tx with Smart Charger

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Old 03-11-2008, 06:54 PM
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hiljoball
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Default Cannot charge Futaba Tx with Smart Charger

I cannot charge the battery in my Tx using a Smart Charger.

I have a Futaba Transmitter. (Model 6EXAS 2.4gig).

I took out the standard 600 miliamp battery and replaced it with a 9.6V 2200 NiMH.

I have a Multi-Current Smart Charger ( 1-2 A ) For any 4.8V - 10.8V NiMH / NiCd Battery Packs.

When I plug in the Smart Charger, the battery is not recognised. ie after the initial red/green test sequence, the light goes out. It should show RED while charging, and change to GREEN when battery is fully charged.

I have checked plug polarity and everything checks out fine except for the NO CHARGE.

If I remove the battery from the Tx and connect it to the charger, it charges fine.

The little wall wart charger that came with the Tx shows charging if I plug that in.

Is there something in the Tx that prevents 'smart chargers' from working. I would like to charge 'in place'. Taking out the battery to charge it is a nuisance.
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Old 03-11-2008, 06:58 PM
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Default RE: Cannot charge Futaba Tx with Smart Charger

I believe the TX has a diode in place that stops charging and discharging a pack through the Tx port if it's not the original charger. I know there is a bypass to the diode but is was something I didn't want to mess with.
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Old 03-11-2008, 07:09 PM
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Default RE: Cannot charge Futaba Tx with Smart Charger

Please check that you are using a Futaba charge lead and not a JR (I did that ones)

Doug.
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Old 03-11-2008, 08:58 PM
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Default RE: Cannot charge Futaba Tx with Smart Charger

The 9CAP series doesn't have the diode, but others do. One easy test would be to do a voltage check through the charging jack. It kind of susprises me that your transmitter might have the diode being it is a 2.4gig. Bypassing the diode is a simple project, if you are familiar with Printed circuit boards and can identify a diode from a resistor by sight. You may void the warranty though.

I would post this over on the Futaba direct support forum and see what Bax has to say. In the mean time, just unplug the battery from the transmitter and use a receiver lead from the charger directly to the battery. That is what I'm doing with mine.

One more point, my charger warns that you should not use more than 1 Amp through the transmitter jack as it may burn out the board. Just something to keep in mind.

Don
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Old 03-11-2008, 09:15 PM
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Default RE: Cannot charge Futaba Tx with Smart Charger

Follow this link. Your Tx needs to have the diode jumped. You can either use a single strand of wire like the picture shows, or you can buy a "Futaba" "Poly Switch" which you jump the diode with. I've used both methods, and as long as you can solder adequately, you should be able to do the job. The poly switch is available from Tower, in packs of two.
Hope this helps,
Sam

[link=http://www.siriuselectronics.com/diode_sheets/futt6EX_24.htm]Sirius Diode Jump Chart- Futaba[/link]
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Old 03-11-2008, 09:19 PM
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Default RE: Cannot charge Futaba Tx with Smart Charger

Thanks Daddysam and all other respondents.

Now I understand the issue and have a solution.

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Old 03-11-2008, 10:47 PM
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Default RE: Cannot charge Futaba Tx with Smart Charger

I jumpered the diode in mt T6XAS futaba Tx. Benn smart charging ever since... no problems.

The jumper location can be found on the futaba web site. I don't know if it voids the waranty though, being that futaba gives you the jumper location and all. but probably does.

I now use a 9C which does not have a diode(I would have jumpered it if it did).

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Old 03-12-2008, 11:26 AM
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Default RE: Cannot charge Futaba Tx with Smart Charger

Jumpering the diode voids the warranty, properly installing a poly switch does not.
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Old 03-12-2008, 11:44 AM
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Default RE: Cannot charge Futaba Tx with Smart Charger

I used poly switches on my T6XAs, 8UAPs and Polks Tracker II. All work just fine. Charge and discharge all the time.

Cheers,

Chip
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Old 03-12-2008, 02:56 PM
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Default RE: Cannot charge Futaba Tx with Smart Charger

You can also just use a different charger that'll charge thru diode.
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Old 03-12-2008, 03:31 PM
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Default RE: Cannot charge Futaba Tx with Smart Charger

The problem is not charging through the diode. The problem is getting voltage/current feedback thru the diode.
The diode acts like a one-way street for electricity.

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Old 03-12-2008, 03:45 PM
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Default RE: Cannot charge Futaba Tx with Smart Charger

Some peak chargers can do it, some can't. Apparently the op's "smart charger" is one that cannot handle the diode for reason above. It may be better to invest $20 in a different charger than to invest $20 for poly switch.

ps what is a poly switch?
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Old 03-13-2008, 11:28 AM
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Default RE: Cannot charge Futaba Tx with Smart Charger

A Polyswitch is a kind of solid state fuse. It can reset itself automatically. they cost less then $0.50 at electronics shops.

http://en.wikipedia.org/wiki/Resettable_fuse
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