How many volts (futaba)

[OceancityMD]

How many volts can my futaba reciever handle??
My ESC keeps cutting out 3 amp bec at 3/4 throttle can I plug a reciever Pack in to keep the voltage up
I am using 3s lipo packs they are getting old cant handle high discharge

[AndyOne]

Most Futaba receivers can handle a fully charged 5 cell ni-cad pack which will be around 7.2V, personally I wouldn't like to use more than 8 volts. A more pertinent question is how many volts can the servos handle, most are rated at 6 volts (5 nickel cells) some are only rated at 4.8V (4 nickel cells). Running servos at over-voltage will burn out the motor or amplifier.

[Malc C]

Andy, isn't 5 cell Ni-cad pack 6V not 7.2 ? (5 x 1.2v)

I think anything more than 6v will damage both receiver and servo. If there are problems with the BEC not being man enough to power all the radio gear, then look at getting a U-BEC from Koolflight and run it straight from a flight pack (8 cell 2400 Nicads for example).

[pilotpete2]

OceancityMD,
I'm confused, the BEC should never cut out in an ESC, if you are drawing too much current thru the BEC it will overheat and eventually fail, but not cut out as in low voltage cuttoff, only the motor should cut out if your pack can't deliver the goods ;)
Pete

[AndyOne]

Malc,

Battery packs are are referred to by their nominal voltage, a Ni-cad nominal voltage is 1.2V and Li-Poly is 3.7V but this is only part of the story.

When you charge a Ni-cad pack the voltage ends up well above 1.2 volts per cell, check your Tx readout at switch on immediately after charge, it can go over 11V for a 9.6V pack.

You have to take into account this maximum voltage when powering up sensitive equipment.

Andy.

[alibodin]

ANdy is correct I recently measure my feeshly charged packs, 5 cells was 6.5V and 4 cell was 5.2V and I have been using them for about a week setting up controls and testing some software,

Alistair

[slipstick]

How many volts can my futaba reciever handle??
My ESC keeps cutting out 3 amp bec at 3/4 throttle can I plug a reciever Pack in to keep the voltage up
I am using 3s lipo packs they are getting old cant handle high discharge
Can you be a little clearer about what exactly is happening ? Unless you're doing something very strange your ESC will be cutting power to the MOTOR not the receiver/servos. That's what normally happens when batteries are weak. There's not much you can do except use a better battery or a smaller prop (to reduce the current the motor takes).

BECs can overheat but that has nothing to do with the throttle setting. So the odds are it has nothing to do with the BEC circuit and adding a battery to provide the relatively tiny amount of power needed by the Rx/servos isn't going to help.

Steve

[OceancityMD]

All my packs @ 3/4 throttle will cut off with this GWesc35A, TP and Tanic 3s lipo
AXI 2816/10 9X6 or 10X4.7 or the like looks like about 18 to 20 amps @160 or so watts is all I can get.the ESC keeps cutting off it has the 3 amp rating

[pilotpete2]

Your ESC is cutting off because your lipos can't maintain adaquate voltage under load, as Slipstick said the BEC is not an issue here, you are pulling too many amps for your lipo packs, if I read correctly you are pulling 18 to 20 A at 3/4 throttle, that means you are pulling a lot more at WOT, what capacity are the packs and what is the "C" rating of the packs?
Pete

[OceancityMD]

TP 2100 think 15C and Tanic 2500 10 to 12 c

[Malc C]

Have a read of the following thread

http://www.rcgroups.com/forums/showthread.php?t=555129&page=2#post5982900

If I follow it correctly, the suggestion is that the ratings for the ESC are the peak rating not constant. So it's possible that it's not a 35 Amp constant rated ESC, so maybe you are pulling more amps that the thing can supply and causing an overload or your ESC is getting too hot and causing a thermal shutdown of the ESC (seems the ESC needs to be kept cool by good air flow

I may be wrong here, but I think that there is a relationship between voltage and current, and if you exceed the current the cells can supply, the voltage can drop, and the voltage drops below the low voltage cut off point of the ESC.

[pilotpete2]

This is where a Watt-meter comes to the rescue, it'll show you exactly what is happening to the pack voltage as you advance the throttle, if the battery voltage is dropping down to LVC at partial throttle either replace the packs with higher capacity or prop down for less current draw ;)
Pete

[slipstick]

All my packs @ 3/4 throttle will cut off with this GWesc35A, TP and Tanic 3s lipo
AXI 2816/10 9X6 or 10X4.7
There's no such AXI motor which makes it hard to work out what you're talking about.

Steve

[OceancityMD]

So you guys think prop down first. Dont I need X amount of watts to fly the plane so no matter how far down I prop I'll still need more stick position right??
I wish these companies had the same standard for rating the ESC's

[OceancityMD]

I'm a firm believer of You get what you pay for 45 bux for the esc and I have problems the motor calls for a 9x6 I have a Thunderpower 3 s lipo 2100 pack 3 of them alll the same result
the ESC seems to be the problem or TP has a bad product this stuff pisses me off to no end when I bough this stuff I looked at ratings and watts I needed to fly and it still dont work AAAAAAAARRRRRRRRRRRRRRRRRRrrr

I mean why should I prop down why dont the packs deliver whats advertised
why doesnt the ESC do what it says 35 amps sheeeeeezzzzzz

OK now the same packs-- himax 2812/850 jeti 18 amp esc & 11x6 prop no problems 3 clicks from WOT 9 min flight go figure

[Malc C]

The other thing that may of been overlooked is that the ESC is actually faulty, causing
a) too much current draw from the packs
b) thermal shutdown
c) incorrect feedback to the LVC circuitry

If its new ask the retailer for a replacement.

The other possibility is the motor is not as efficient as the Himax (or possibly that has a fault and is drawing too many amps). Try the Himax and GWS esc to see if that has the same effect !