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Futaba FASST Transmitter max voltage.

Old 06-30-2011, 08:29 PM
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Electrolight
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Default Futaba FASST Transmitter max voltage.

So I have some spare Samsung 3000 mah, 3.7v Lithium Ions (4.2v fully charged)... I want to replace my 9.6 600 mah NiCd... So I was wondering... what is the max voltage that I can safely apply to my transmiter?

Any thoughts?
Thanks!
Old 06-30-2011, 09:31 PM
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BuschBarber
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Default RE: Futaba FASST Transmitter max voltage.


ORIGINAL: Electrolight

So I have some spare Samsung 3000 mah, 3.7v Lithium Ions (4.2v fully charged)... I want to replace my 9.6 600 mah NiCd... So I was wondering... what is the max voltage that I can safely apply to my receiver?

Any thoughts?
Thanks!
9.6v batteries are commonly used in Transmitters, not Receivers. Receivers commonly use 4.8v or 6v batteries. Your receiver should operate with 2cell LithIon Rx packs (8.4v). It is the Servos that limit what Rx voltage you can use. Unless the Servos are labeled HV, they are probably limited to 4.8v or 6v. The Servo box should list the Servo Speed and Torque for each voltage range.

If the servos only work with 4.8v or 6v, you can still use 2cell LiPo or LithIon Rx packs, but you will need to use either a 5v or 6v Regulator.
Old 06-30-2011, 10:37 PM
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Default RE: Futaba FASST Transmitter max voltage.

Thank you for your input! But I meant to say transmitter not receiver... I fixed my OP... But ya I'm basically wondering if I can connect 3 X 3.7 v Lithium Ion 18650's for my transmitter (directly and have the transmitter be ok) or do I have to add a buck converter to drop the voltage ( they are pricey so if I could just do 3 lithium I could save some nice coin and multiply my transmitter battery life by 5 (and lighten it by 55 grams lol))
Old 07-01-2011, 05:21 AM
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Default RE: Futaba FASST Transmitter max voltage.


ORIGINAL: Electrolight

Thank you for your input! But I meant to say transmitter not receiver... I fixed my OP... But ya I'm basically wondering if I can connect 3 X 3.7 v Lithium Ion 18650's for my transmitter (directly and have the transmitter be ok) or do I have to add a buck converter to drop the voltage ( they are pricey so if I could just do 3 lithium I could save some nice coin and multiply my transmitter battery life by 5 (and lighten it by 55 grams lol))
For many years, most transmitters came with 9.6v batteries. Some newer transmitters operate on a lower voltage. I have two JR 9303 transmitters, a Futaba 9CAP and a Futaba 8AUPS. I have been using unregulated 3cell 2500mah LiPos for the past 4 years, without issues. There are threads, on RCU, where modelers have used inexpensive Diodes, from Radio Shack, to drop the voltage of the transmitter LiPo pack .3v per Diode. I do not know the exact part number. Some just charge the transmitter LiPo pack to 11.7v (a fully charged 3cell LiPo is 12.6v). You can buy transmitter LiPo packs from many sources.

A good alternative is a LiFe pack (lower voltage) or Eneloop batteries (but now you are adding some weight as these are a form of NiMh).
Old 07-01-2011, 10:19 PM
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Electrolight
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Default RE: Futaba FASST Transmitter max voltage.

I really don't mind weight. I decided I's make my own pack of NiMh batteries with Eneloop batteries. Better safe than risk it with the 3 cell lithium ions. (normally I would because I don't mind messing up something in the pursuit of knowledge... but I just don't have the cash for another receiver) (I got the slightly more expensive version that has 1500 cycles). I think by the time I hit 1500 cycles It will be time for a new receiver lol

But thanks!
Old 07-05-2011, 11:25 AM
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Electrolight
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Default RE: Futaba FASST Transmitter max voltage.

Just reporting for others out there... My NiCd pack was old and apparently had a terrible memory effect affecting it... So I finally made my NiMh pack and I'm just reporting that WOW what a difference. I went from 45 minutes of operation to 6 hours of operation. Those Eneloop cells also use some fancy chemistry to keep them from having a memory effect so I think I will be able to count on them for years to come.

Anyways have a good day!

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