BEC's? whats the advantage? also, what servo

[axeten]

I just bought an Axial AX10 scorpion kit and will be running the Tekin FXR/45t combo with an intellect 2300mAh lipo. Still need to get a higher torque servo.

The tekin says it has a built in BEC (6V) so what is the advantage of running a castle creations one seperate? I have searched BEC to try and find out, but all i can find is that you should run them. fair enough with a 3S lipo but isnt the internal tekin one going to be ok with my 2S? why does it seem to be so important to run a BEC in crawlers when i have never run one in my tourer/1/12th scale/F1 or electric offroad?

Also, what is a decent servo to use for steering. i only wanted to spend around $50 but it seems that wont be enough? any suggestions on cheapish ones?

thanks
Alex

 

[Sharkey]

the internal bec in the tekin is 6v 3a, it is enough to run one servo on 2s. a rock crawler puts a lot more strain on the servo and stalling a servo is common, and a servo at stall draws a lot of current, some high end digital servos will pull over 4 amps at stall. with 3s lipo the internal bec tends to become weaker and shutdown can become an issue. for most budget servos, the internal bec should work fine. i dont have issues with a single hitec 645 on my crappy esc's internal 5v 1a bec.

for a good servo, the hitec 645 is decent for the money, or for a few bucks more go with the digital version, the 5645. the hobbico cs150 is also a decent servo for the money

 

[Duuuuuuuude]

X2 on what Sharkey said. The 645 and 5645 are good servos with a fair amount of power. I've got both and like them. They also do not pull enough amps to make a bec mandatory if you have a decent esc.

I run a 5645 and Sidewinder in my sportsman rig, minus a bec. Never had a stalling issue.

 

[KBrog]

When I ran a Sidewinder on 3s I would get the steering in a bind and the whole thing would cut out. Would lose power to everything. I could pick the ruck up and get it out of the bind and everything would come back on. I installed a BEC and everything worked great after that.

 

[Duuuuuuuude]

When I ran a Sidewinder on 3s I would get the steering in a bind and the whole thing would cut out. Would lose power to everything. I could pick the ruck up and get it out of the bind and everything would come back on. I installed a BEC and everything worked great after that.

What servo were you running?

 

[canibalpenguin]

I think he's asking more about what a bec is.
A bec (battery eliminator circuit) i more or less a voltage regulator. It allows you to run run a vehicle (elec) with just the main battery which is usally 7.2v or more with out having to use a rx batt for the servos which usually only run at 6v. Almost all esc and rx have bec's built in to them and limit voltage to 5 or 6v to the the radio gear. i would be willing to bet if you checked the cases of your gear or the specs of the gear for your other cars you find that they have bec's. As far as needing an external bec, that depends if your rx/esc has a bec. If not then get an external,i fthey do, don't worry about it.

 

[landon4]

A built in bec is not enough especially if running a 3s, the only esc with a built in bec that is powerful enough is the Holmes BR-XL and the Mamba max pro the only downside which isn't much is that they are bigger and would be a little tighter fit on some chassis, but I would run the cc bec on any crawler as it is only $20-$25.

 

[Duuuuuuuude]

A built in bec is not enough especially if running a 3s, the only esc with a built in bec that is powerful enough is the Holmes BR-XL and the Mamba max pro.

Not always.

 

[Rthlss]

The 645 is a good one, at 133 oz/in torq, it will get tired eventually...
The 5645 is not bad either at 164 oz/in torq.. However I like to recommend for a crawler to have 200 oz/in or more..
Spektrum just released a new servo that they say is for aircraft, at 278 oz/in of torq I have been selling them as steering servos for crawlers with much success, with titanium gears all the way thro and a price tag of only about $85 its a great choice for the beginner..


http://www.horizonhobby.com/Products/Default.aspx?ProdID=SPMSA6030

 

[rmdesignworks]

Not always.

X2,,,the only one powerful enough huh,,someone better tell my rooster crawler it isnt powerful enough to drive the ds8711 then,,yeah my servo gets warm cuz it does need a bit more than the 5amps that the rooster puts out but it does the job even in bad binds...i am waiting to get my ccbec back from repair but the N.R.C. is doing the job.

6vdc @3amps is pretty low though even for a 645 sized servo,,if the internal bec is only putting out 3 amps i would add the external ccbec

You really need a servo pushing 300 plus ounces,,,ds8711, or ,one of the new futaba high torques,,or one of the new hitec high torques

 

[landon4]

X2,,,the only one powerful enough huh,,someone better tell my rooster crawler it isnt powerful enough to drive the ds8711 then,,yeah my servo gets warm cuz it does need a bit more than the 5amps that the rooster puts out but it does the job even in bad binds...i am waiting to get my ccbec back from repair but the N.R.C. is doing the job.

6vdc @3amps is pretty low though even for a 645 sized servo,,if the internal bec is only putting out 3 amps i would add the external ccbec

You really need a servo pushing 300 plus ounces,,,ds8711, or ,one of the new futaba high torques,,or one of the new hitec high torques

All this makes sense but the Rooster is only good for a 2s lipo plus it is geared towards crawlers so it has a better built in bec, but I'm saying with running a 3s lipo, my son had a rooster in his rig with a 645 and 2s and yes it did great but I know in my scaler with a sidewinder and 3s with a 645 it would cut out until I added a ext bec then I had no more problems out of it.

 

[axeten]

Thanks heaps everyone.
I did know what a BEC was, i just wasnt sure why external was needed (prefered) when the ESC has one built in. Like you's say though, your talkin much more stress and power pulled compared to a touring car.

The Tekin that i have on the way has a 5A built in. and running a 2S with a cheap no brand servo (around 100oz). I will run it and then save some cash up.
I think i'll get this:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=330375211518&ssPageName=STRK:MEWAX:IT
and just run it at 6v with the castle creations BEC.

thanks again and i look forward to gettin this thing running

Alex

 

[spcpicard]

On my son's axial, he's running the CC sidewinder with the Hitec 7955tg. He's running it on 2s lipo so I just pulled the red wire on the esc and wired a battery servo connector in line (parallel) with the Battery connecters coming from the esc and feeding the full 2s lipo voltage into the reciever. The servo gains alot of torque and speed, and the esc runs cooler. Keep in mind that your receiver and servo have to beable to handle the higher voltage.