BEC vs Rx pack?

[snowhack]

I have a MM and w/ 3s Li-Po and a future 8T conversion would warrant a 4s Li-Po. Do I need the castle bec or can I use the rx pack I already have? I know the added weight is a dis-advantage, but what other problems would I face if any? I never hear anyone talk about Rx packs in Nitro/BL conversions. Thanks.

Originally Posted by snowhack

I have a MM and w/ 3s Li-Po and a future 8T conversion would warrant a 4s Li-Po. Do I need the castle bec or can I use the rx pack I already have? I know the added weight is a dis-advantage, but what other problems would I face if any? I never hear anyone talk about Rx packs in Nitro/BL conversions. Thanks.

besides the weight factor, if the voltage gets too low you would lose the signal like a nitro vehicle can, but than you wouldnt have to worry about the BEC failing and the possilbilty that some components could fry

[GorillaMaxx360]

If i am not mistaken you can use a Rx pack instead of the bec. To my knowledge the bec takes electricity from the main battery source and sizes it down to about 6 volts(adjustable but just an estimate) for the servo. I have used a Rx pack instead of a external ubec on my maxx and worked great. Basically the Rx pack is powering just the servo so no battery juice is drained from the main source of power (with BTW is not much loss of runtime). Many people chose the bec over the Rx pack because it is no maintenance, light, adjustable, and one less thing to charge. On the other hand most people chose the Rx pack if weight is not an issue, they don't want to solder, would prefer to charge and extra battery to get more runtime, to keep it simpler, or they just don't understand how the bec works. For your situation the Rx pack would work fine and i would not worry too much about the weight because it is not very heavy. Also if positioned in the right place it could allow for more steering or rear traction ect...

[DRIFT_BUGGY]

Well said GorillaMaxx360. A CC BEC is only $24 aswell

[Steve Krug]

I bought a CCBEC, but then it failed before i even used it for the first time...so now i use an RX pack and it works flawlessly.

[Sammus]

Ive had a faulty ccbec 2 out of 8, both times castle replaced them for nix.

[snowhack]

Thanks guys. I figured that no mention of anyone using it meant it was avoided for some reason. I probably will go w/ the BEC, but good to know I can use the rx pack if I want to.

[RBMike]

I had to abandon the CCBEC. It was causing glitches & even a couple of run-aways in my buggy conversion. This happened with 3 different Spektrum RX's. I have used an RX pack & it worked fine but I did not want it in the buggy so I got an analog Novak BEC & it is working fine for 2 days of running so far. FYI

[lincpimp]

Everything already said is true. I would add that a bec can produce some interference that could cause glitching, depending on its placement and the type of radio you use. A rx pack will not cause glitching. I generally use ubecs as I do not like charging extra batteries, and it is lighter. For your setup it may not make any difference...

[redshift]

My CC BEC also smoked before I got any use out of it. Maybe I'm better off for it if it's a source of interference. I went to my LHS and surprise, no 4/AA clips (they never have anything I need)
So I ended up at RadioSnack and (grr!) all they had was a 4/AAA clip, so I got that along with 4 750mAh Nimh AAAs. I was thinking "this'll run my radio for about 15 minutes" but actually it's working quite well, Over 90 minutes before it got below 5V!

I'd say if you're not racing, or overly concerned with the little extra weight, go with a clip/pack and not a bec.

[BrianG]

As far as noise goes, the Koolflight UBEC, Hercules HVBEC, and DimensionEngineering UBECs all had noise levels too low for my Fluke to measure. I usually get ~3-4mV of noise, but I get that with the meter leads shorted, so I generally set that as my baseline "0v".

The CCBEC and the cheaper chinese UBECs (even though they are based off the same IC as the KF one) had some level of noise.

It would be a little cumbersome, but you could use a CCBEC set at 7.5-8v, and then a linear regulator IC (LM317T available at RadioShack) and a pass transistor (to boost the current to over 5A) to regulate the rest of the way down to 6v. This might seem a bit stupid, but it does 2 things: 1) filters out the noise since, by nature, a linear regulator "chops" off the top of the voltage where the noise is, and 2) if the CCBEC failed and sent full V to the output, the linear regulator would get hot very soon and thermal - but that's better than toasting a few hundred dollars in electronics! But if the CCBEC works like it should, there is hardly any efficiency losses in the linear regulator because the difference in voltage between the input and output is so small.

[RBMike]

While I was trouble shooting these glitches at one point I had an RX pack running my radio & the CCBEC just running my fans, still glitched. I could not even have the CCBEC wired to the ESC, not supplying power to anything, just sitting in the car with the input wires to the battery, still glitched.

[Sammus]

Any way (apart from what brian mentioned) to stop the ccbec causing glitching? Is there anything wrong with the placement in this pic? I've had some shocking glitching issues in this car (and my rustler when I had a the bec in it. Revo is fine). Is that a little too close to the Rx perhaps?

[snowhack]

All that being said right now I am running my MM in my XXXT. The set up is

...Mamba Max w/ latest FW, no fan yet. (9v c/o and factory defaults)
...TRX Velion 3500kv BL motor, no heat sink/fan.
...FM radio. (my 8T has the Spectrum)
...(2) 11.1v /3s /2200mAh /25-30C Li-Po's (Parallel for 4400mAh.)
...86t spur/19t pinion.
...sans wheelie bar. (has more wear on lid than tires)
...2.2 Yakahamas. (all arround)

I do not presently use a BEC or Rx pack, am I taxing my servo?

[suicideneil]

Sammus - looks like your BEC is located right next to the Rx; I would move it as far away as possible to reduce glitching (Rxs are more sensitive than the esc I think).

Is there any real issue with using a normal linear voltage regulator instead of a BEC? Im assuming it will result in less glitching caused by noise, but run warmer (not an issue really)...