Seperate battery for servo

[darkangelv24]

Right, i know this isnt the normal way of doing things but im a bit pushed for time. I have a high voltage servo (7.4) in my wraith which is pushing some heavy weight wheels. i dont have a spare castle bec at the mo and wont be able to get one in time for when i need it. The rig is also running a 3s battery.

So my question, in order to power the servo at 7.4 V could i remove the red and balck wires from the reciever leaving only the signal wire in place, then wire in a small 2s battery directly to the servo?

[Johnnysplits]

That will work, but you need to leave the ground wire besides the signal wire.

[darkangelv24]

so i need a negative to the battery and reciever?

[Johnnysplits]

You can use a "Y" connector. Plug servo into the Y. Remove the positive lead from one plug and run it to the Rx. Remove the signal lead from the other plug and then connect the positive and negative leads to the battery. There are places online that make plug and play harnesses to do this, but this way is less expensive.

[Calderwood]

If the servo pack is lipo then it will need a separate lipo cut off as well.

[Trubble]

Before I got my BEC, I pulled the red wire from the ESC's connector and ran the 2S in an open slot on the receiver. Worked fine. I'd imagine if you wanna go direct, that'd work equally well.

Originally Posted by nigels_world

If the servo pack is lipo then it will need a separate lipo cut off as well.

Yup! Luckily my Heli LiPos have a built in cutoff/balancer board. 500mAh got me somewhere in the neighborhood of 20-25 minutes.

[darkangelv24]

i think your right running the whole reciever off the 2s pack will prob work best. so remove the red wire from the esc.

thats prob the simplest bit of wiring as its only for the weekend. will order a castle bec and do it properly after that.

[Dostradamas]

I am planning on running a LiFe 2s (6.6V) RX pack, do LiFe packs need a low voltage cutoff as well?

[Calderwood]

Originally Posted by Dostradamas

I am planning on running a LiFe 2s (6.6V) RX pack, do LiFe packs need a low voltage cutoff as well?

That depends on who you ask...

[Dostradamas]

Originally Posted by nigels_world

That depends on who you ask...

OK what do you think?

[Calderwood]

Originally Posted by Dostradamas

OK what do you think?

I wouldn't be using a rx pack in the first place since I don't run nitro but if i was using a life pack I would put it on a lvc set for 2.2 volts or so per cell just to be safe. Maxamps says you don't need one though, if you trust they say.

[AutoCrawler]

Originally Posted by Dostradamas

I am planning on running a LiFe 2s (6.6V) RX pack, do LiFe packs need a low voltage cutoff as well?

I have read that LiFe's typically operate in the 3.0 to 3.3 v range and that they are damaged if you discharge them below 2.1v. I have also read that they "cut off themselves" at around 3v whatever that means.

From that I think its a good idea to have a battery alarm or cutoff somewhere between 2.1v and 3.0v. Closer to 2.1v to maximize run time and closer to 3.0v to to warn of impending doom

[Dostradamas]

Originally Posted by AutoCrawler

I have read that LiFe's typically operate in the 3.0 to 3.3 v range and that they are damaged if you discharge them below 2.1v. I have also read that they "cut off themselves" at around 3v whatever that means.

From that I think its a good idea to have a battery alarm or cutoff somewhere between 2.1v and 3.0v. Closer to 2.1v to maximize run time and closer to 3.0v to to warn of impending doom

Indeed.
I am new to the LiFe's & am planning on a digital voltmeter onboard & I will just have to keep an eye on it.
I am going to try running my rx / servo off the LiFe & the ESC/Motor off my 3s LiPo

[Calderwood]

Originally Posted by Dostradamas

Indeed.
I am new to the LiFe's & am planning on a digital voltmeter onboard & I will just have to keep an eye on it.
I am going to try running my rx / servo off the LiFe & the ESC/Motor off my 3s LiPo

I'm curious as to why you are doing this instead of an external bec?

[Dostradamas]

Originally Posted by nigels_world

I'm curious as to why you are doing this instead of an external bec?

Fried my CC BEC & this will be a cheaper fix &
To confirm / deny my personal curiosity of why not.

$16.94 for LiFe & onboard voltmeter shipped to my door.

[Calderwood]

Originally Posted by Dostradamas

Fried my CC BEC & this will be a cheaper fix &
To confirm / deny my personal curiosity of why not.

$16.94 for LiFe & onboard voltmeter shipped to my door.

How did you kill the bec?

[Dostradamas]

Originally Posted by nigels_world

How did you kill the bec?

Stupidity.
Testing with exposed wires & shorted input power wires.

Here is what I am getting. I will probably attach the meter to the pack & the meter plugs into the balance plug & checks cell voltage & cycles back & forth from 1 to the other (with 2s)

[Johnnysplits]

Originally Posted by Dostradamas

I am planning on running a LiFe 2s (6.6V) RX pack, do LiFe packs need a low voltage cutoff as well?

No they don't. You can beat life's like a rented mule and they come back for more. Been using them for six years now... great batteries.

[AutoCrawler]

battery alarm
Amazon.com: Bluecell 1-8 Cell Lipo Digital Battery Voltage Checker with Warning Alarm + 2-6 cell Lipo Digital Battery Voltage Checker: Toys & Games

Alarm connects to balance connector 2s-8s and is settable between OFF and 2.7-3.8v. It chirps loudly a few times when the the voltage you set is reached then stops.

The voltage meter is just a 2-6s voltage meter thrown in which does the same display thing.

[monkeyracing]

Back to the original question: Yes, you can, and you can probably run just the signal to the servo, but its just as easy to only disconnect the red.