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Futaba 9 Cap with a 11.1 Lipo... safe?

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Old 02-14-2012, 04:58 PM
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Richard39
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Default Futaba 9 Cap with a 11.1 Lipo... safe?

I have been using a 11.1 Lipo battery in my Futaba 8U and it works fine.... I just acquired a used 9C Futaba transmitter and want to up grade the battery with a lipo 11.1 battery... Is it safe to do so in the 9C.... I have a couple of 11.1 transmitter batteries and would like to to use them.... thanks..
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Old 02-15-2012, 11:04 AM
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Default RE: Futaba 9 Cap with a 11.1 Lipo... safe?

Is there any info out there on using lipo batteries in Futaba 9C? is it safe for the transmitter to use the lipo batteries?
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Old 02-15-2012, 11:47 AM
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Default RE: Futaba 9 Cap with a 11.1 Lipo... safe?

Did it use the same battery as the 8u?

If the 8u used 8xAA it will be safe as the AA will have a voltage of at least 1.5v when full charges (12v), very similar to a fully charged 3 cell lipo?
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Old 02-15-2012, 04:07 PM
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Default RE: Futaba 9 Cap with a 11.1 Lipo... safe?

The 8U used the Futaba battery pack that came with the radio ... 8 batteries...( 9.6 volts?) I am not sure but are all rechargeable AA batteries 1.2 volts? I would think that both radios, the 8U and the 9C used the same battery pack but I am not sure....
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Old 02-15-2012, 11:34 PM
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Default RE: Futaba 9 Cap with a 11.1 Lipo... safe?

AA batteries have a stated voltage of 1.2 but when charged this is much higher, 1.5 or more.
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Old 02-16-2012, 07:45 AM
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Default RE: Futaba 9 Cap with a 11.1 Lipo... safe?

No, they will max out between 1.4V and 1.45V, but this voltage will drop off like a rock as soon as a load is applied. A 9C will display 11.4V at most fresh off charge with Nimh or Nicd, and quickly drop to the high 10's.
A Lipo will deliver 12.6V for some time. The issue is with the radios regulator, at that voltage it will run hotter. Now the bigger issue comes in with running a 72Mhz RF module. In this case there is no voltage regulator. Full battery voltage is used for the final RF output. Futaba Mhz RF modules were not very tolerant of running with the antenna collapsed for any length of time. Run a full 12.6V to the RF module and then do a range test, that extra voltage will eventually kill the output transistor. The safest way to run a 3S lipo in any 8 cell transmitter is to add 2 diodes in the battery output. That will drop the 12.6V of the battery down to about 11.4V to the radio (I've done it with my 9C), better yet, if you run it to low voltage warning, then the lipo will not be over discharged. Adding the diodes also has the added safety benefit of disabling the regular charge jack, you will only be able to charge thru the balance tap, a good thing in my opinion
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Old 02-16-2012, 11:51 AM
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Default RE: Futaba 9 Cap with a 11.1 Lipo... safe?

I have been using my 9 cap with 3s lipo for the last 3 years and works fine.

Take carte to charge lipo outside of radio.

Cheers,

Juan
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Old 02-17-2012, 02:46 PM
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Default RE: Futaba 9 Cap with a 11.1 Lipo... safe?

Thanks to all for the replies....
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