Lipo Direct to Servo Help!!
 

Hi guys,
Was speaking with my LHS today regarding becs, he's said that another option is directly wiring my servo to a 7.4v 800mah lipo. A) does anyone have diagrams for this? B) My receiver has a BATT channel, can I just use that?

If your receiver can handle 7.4v nominal you would be able to power it like that. Typically people buy a short servo extension, cut the red(+) wire and plug it in between the ESC and receiver. This stops the ESC from supplying power to the receiver and servo. Then plug your secondary power source in to the receiver. The batt channel would work fine. Again, this can only be done if the receiver supports that high a voltage.

There are wiring diagrams out there for supplying power directly to the servo while only keeping the signal wire of the servo connected to the receiver but i haven't done it.

Remember that a fully charged 2s lipo carries 8.4v. A servo or rx that can't handle that much voltage will go poof.

A bec is a safer, less hassle free way to go.

Poof is never a good thing. :)

A BEC isn't necessarily safer. If/When it fails all your stuff will fry if it's not HV rated. Running a separate lipo with HV equipment all but guarantees that there won't be a failure do to over voltage, etc... I had a BEC fail and watched the servo and ESC meltdown as I tried to unplug the 4s battery as fast as I could. Surprisingly, the receiver was/is fine.

If a failed bec caused an esc meltdown, you did something wrong like not pulling the + wire out of the esc to rx plug. $1 says that is what you did.

I've had one bec go bad and pump full battery power into my rx and servo. The servo eventually died, the rx was fine.

An 800mah lipo is going to power a servo under load for about an hour, maybe two. You'll have to worry about over discharging and making sure it is charged every time you go out. Not to mention is it quite a bit bigger than a bec.

My esc doesn't have a built in bec, so you're right. I didn't pull the wire because it's not required.

In my setup I use either a 300 or 460 depending on the weight I want. the 300 gets me through a pack without having to worry at all about the voltage level (although my telemetry monitors it and will alert me if it's low), and the 460 will get me through 2 packs. The 300 is the same dimensions as a castle 10 amp bec, the 460 is about 1.5 times the size.

WOW that would be a really small 2s 300mAh lipo. Question, how did the ESC get power from the receiver??? Makes very little sense. What ESC is it?

Yah, it's very small.

http://www.hobbyking.com/hobbyking/s...arehouse_.html

The ESC is a Castle Mamba Max Pro 1-cell.
http://www.castlecreations.com/produ...o-onecell.html

I run my Losi 22T on 6S, and it's about the only ESC that is reasonable in size (I only know of one other) that will handle that voltage. This particular ESC still keeps the 3 wires to the receiver for programming (even though there is no BEC), which is how it got the power back. The ESC on 6S is the smoothest/best I've felt. I haven't driven all brands, but close.

Here is a pic of my setup. You can see the 460mah battery just in front of the big one, and the ESC in front of that.

http://i514.photobucket.com/albums/t...ps02fe062b.jpg

Buy the castle bec... Program the bec... Get out the soldering iron... Solder the red wire to red wire on battery connector.... Black wire to black wire on battery connector... If not the mamba 1-cell, remove red wire from plug that goes to the rx... Plug bec in to battery slot on tx... Done! No need for additional batteries to manage, and extra weight... All that for a whopping $20... I cant for the life of me, understand why some people on these forums are so afraid of a bec... But will add an additional lipo into their car???

Speaking for myself, I'm not afraid, just not trusting. As I said, I've had one fail and don't want it to happen again. Plus, I like having the separate power supply not connected to the motor.

Edit: Additionally, the lipo is easy to move around if I want to try a different weight arrangement.

I was trying to think of an esc with no internal bec that could handle that much voltage. There is it. :lol: