JCINTEXAS

Can I used a 2S LiPo 7.4v battery for my receiver battery? This question pertains to late model Futaba and Spectrum receivers and Digital servos (not the High Voltage servos). This has been a topic of discussion in our flying group. Some guys say they are doing this and it's working fine. Some others say you need to use a voltage regulator to drop the voltage. Is anyone out there running unregulated LiPo 7.4v packs? Any information on this would be appreciated.
Best Regards
JC

I don't always fly R/C...but when I do, I fly FASST. Fly well my friends.

sidgates

My Feedback: (2)

My persnal opion is I would never run srevos, receivers or transmitter above their rated voltage.

JCINTEXAS

Thanks Sid. I'm agreeing with you. Just wanted to see if this is working for other fliers out there.
Regards
JC

DrV

My Feedback: (2)

The Rx "may be ok" (I would not do it) but the servos will burn out if not high voltage. Most current Rx have a regulator inside but output to servos are not regulated. I personally would use a regulator if using 2s LIPo. You can use unregulated 6.6v (2s) LiFe( A123) to Rx and most servos that are rated for 6v (meaning rated for 5 cell NiMH or Nicd) will be just fine. Lots of discussion about this in the jets forum if you do a search for it.

Good luck

JCINTEXAS

Thanks DrV. I'm gonna go with LiFe
JC

Mad Wax

I'm wondering could you drop the voltage (resistor?)

Goldenduff

Yes, many do. You can even buy a regulator however you are introducing more points of failure.

flyinwalenda

My Feedback: (5)

I'm running regulators on LiPo receiver packs with no problems .

IronButterfly

Not sure 8.4V, full charged Lipo is safe for your electronics.  I wouldn't chance it.  However I do use a 2s Lipo in my Futaba 6J transmitter but with a 1N4001 diode (cheap and available at Radio Shack) in series with the pack.  It drops the voltage about 0.8V.  The 6J normally uses 6V alkaline battery set.  I don't know how well your rcvr/servos will work as the battery discharges.  The 0.8V drop could be a problem. 

IB

BarracudaHockey

My Feedback: (11)

Receivers are fine, servos.....maybe if they are rated 6v but not HV. So...if the answer is maybe, then why take a chance?

Regulate or get A123's

You know the A123 won't burn up in a crash

mehrshad

Life and lipo both chrage to 4.2v/cell and 8.4v for a 2s pack.

pilotpete2

No, they do not.
A LiFe, or A123 pack will come off charge at about 3.6V and drop to its nominal voltage of 3.3V per cell very quickly.
Pete

mehrshad

Sorry your right.
I was confusing with li-ion...

Flying Brick

Using a resistor would be highly unsafe. As it acts as a current limit, the voltage dropped across it will vary wildly. Typically if a 100 ohm resistor is used it may vary from 1v at rest to 4v when 4 servos are active, see ohm's law. If you know anyone using a resistor bring a dustpan and brush.