HV BEC pro questions - RC-Monster Forums

lincpimp · **HV BEC pro questions -** 08.13.2009, 01:15 PM

Just got the latest rcdriver and was thumbing thru it...

Saw Chris's article on the hv bec pro and he had that it was only good to 6s lipo when using motor brakes...

If this is true it is not much use for us HV car guys...

Hope not as I would like a cc product to use, the HC hv bec that I currently use works fine, but is a bit bulky and is not 1 piece.

Anyways, good article Chris!

TexasSP · 02:27 PM

This should help answer your questions.

http://www.castlecreations.com/products/ccbec.html

It shows car limited to 6s, planes 10s, and helicopters with disabled brakes at 12s.

Possibly it could be pushed to 8s with proper cooling?

MetalMan · 08.13.2009, 03:13 PM

I'm having a bit of a tough time wrapping my head around the low voltage rating for cars. Without seeing the RC Driver article I can guess that CC sets that voltage limit due to ripple? If that's the case, couldn't we just use some HV low-ESR caps right at the input of the BEC? It has helped with the MM on higher voltage...

BrianG · 08.13.2009, 03:23 PM

From what I understand, it's not so much current ripple, but because of the potentially huge voltage spike when braking. Makes sense really.

MetalMan · 08.13.2009, 03:24 PM

Well, the MMM has a TVS to prevent such voltage spikes from causing problems, right? Surely there's something we can do here... 6s is unacceptable IMO.

emaxxnitro · 08.13.2009, 03:41 PM

just use mech brakes

BrianG · 08.13.2009, 03:43 PM

The problem is, at higher voltage, those spikes increase by a large order of magnitude. And the energy contained in those spikes at those voltages is quite substantial. The TVS can only absorb so much/so often before it overheats. You'd have to parallel a bunch of them to handle it, and there goes the cost and size of the circuit.

shaunjohnson · 08.13.2009, 05:30 PM

Quote:

Originally Posted by BrianG

From what I understand, it's not so much current ripple, but because of the potentially huge voltage spike when braking. Makes sense really.

yeah +1 on that

sikeston34m · 08.15.2009, 11:54 PM

One thing I really do like about this particuliar BEC is, it's wide range of output voltage.

It goes all the way up to 12.5 volts.

This allows it to be used as a voltage regulator in a number of mad projects. LOL

I've been thinking about getting one of these:

http://www.lasonic.com/store/pc/view...?idproduct=208

It's an "ipod Dock" disguised as the old style boom box. Yes, it brings back memories for me.

I like the fact that this one accepts a memory stick for mp3's.

Anyways, a CCBEC Pro would regulate 4S Lipo voltage to a cool 12.5 volts.

Add a protective PCB with balancing to the Lipo packs used to power the CCBEC Pro and you have rechargeable tunes.

In a not so demanding setup such as this, I'm sure cycle life would be greatly improved.

BrianG · 08.16.2009, 12:25 AM

sikes: Personally, it would be easier and cheaper just to use an LM7812 regulator IC, especially since we're talking only a voltage differential of ~2-4v and probably around 500mA,

sikeston34m · 08.16.2009, 06:46 AM

Quote:

Originally Posted by BrianG

sikes: Personally, it would be easier and cheaper just to use an LM7812 regulator IC, especially since we're talking only a voltage differential of ~2-4v and probably around 500mA,

Aaaah yes

I noticed this unit can be ran from a 12 volt 3.5 amp power supply.

A couple of those in TO-220 form ran parallel, perhaps with a small heat sink should do the job.

Wow, those really are cheap.

Thanks for the tip Brian.

Arct1k · 08.16.2009, 09:00 AM

Sorry been away for the week - I had thought about this when writing the article but ended up getting back to the fact that if you are running a HV setup then generally you are going to be running mechanical brakes and therefore should have no issues.

It is now wired up into my super rock crawler which is not really taxing it at all...