Esc question

[cjcj1949]

With a BEC you are ok up to the BEC's rated current. If you exceed that current (even for a short time) the BEC will probably shut itself down. With a lipo the volts will just drop a bit further. Many people seem to be using the OPtipower Backup Guards to provide a system that copes with peak currents. Modern servos are very good at asking for lots of current for a short while.

If you can separate the power supplies for the servos from the flight computer electronics it will be a good idea as short losses of servo control will be easier to recover from than total loss of the flight computer.

[Grumpy]

With a BEC you are ok up to the BEC's rated current.

Also bear in mind that for most BECs the rated current is not as simple as a single number. Most have a peak/burst rating, which is often the headline rating on the label, but also a lower continuous rating. The continuous rating in most cases depends on the input voltage, higher input means that the continous rating decreases. So it's all a bit complicated.

For example the Castle BEC Pro:

20 amps peak**
Max continuous current**
16 volts input = 15 amps
24 volts input = 13 amps
32 volts input = 11 amps
40 volts input = 9 amps
48 volts input = 8 amps

**Ratings are determined with a 5mph airflow on the BEC

Other manufacturers may not publish the figures but that doesnt necassarily mean that they arent subject to similar limitations.

[tomatwalden]

Also bear in mind that for most BECs the rated current is not as simple as a single number. Most have a peak/burst rating, which is often the headline rating on the label, but also a lower continuous rating. The continuous rating in most cases depends on the input voltage, higher input means that the continous rathing decreases. So it's all a bit complicated.

For example the Castle BEC Pro:
....

+1 on this. This caught me out with my G630 which I naively soldered up for 48v input originally before I realised this!

[treff]

Thanks very much for all this very good info. I have gone for YEP 150 ESC( Cheap) with a Castle Creations 20 amp BEC ( did not know I also need usb link to program voltage)
I will also get an failsafe device but only after I sell the house and car lol. My rush of blood in buying a 5.5 as turned into a fatal haemorrhage either my wallet or my
brain will burst, not sure which will go first lol. Thanks again

[philipjdall]

I guess it depends on the esc... I have run a jive 80LV in my logo 550sx for the past 18 months and it hasn't given me a moments trouble. It also comes down to pitch timing - If your bogging the thing down you're going to cause higher amp spikes.

I'm not sure a castle 80 has as much headroom as a konny though

[tomatwalden]

treff - I think the default output voltage of a Castle BEC is 6v (I wouldn't swear to this though - best do your own research to be sure). You only need a USB link if you plan to change that.

[Grumpy]

Or if you like, post the CC BEC to me I'll program it to whatever voltage you want and post it back.

[treff]

Thanks again all for the info and to Grumpy for the generous offer. Very nice people on this forum. Yes being an old fart on a small fixed income
the better half is beginning to wonder why were are eating beans on toast at regular intervals now lol. Grumpy I won't take you up on the very kind offer because I now have to save for 2 sats
and a decent 6s battery so I may as well throw in a little extra for the usb link. I will put the heli on a shelf and gaze in longing lol. One thing it will stop in one piece a little
longer without a battery lol. Thanks again guys very much appreciate the thoughts. I can still get out and fly my 450 so I have something to practice on. Cheers

[Grumpy]

Treff,
I've got a couple of the CC programming dongles. Whatever the new price is, you can have one for half, if interested.

And by the way, you could save a fair bit of cash by getting a pair of 'Lemon' brand DSMX satellites. Once you get past the name these are every bit as good as the Spektrum originals and a fraction of the price. I have no hesitation in using them: Lemon DSMX Satellite (DSM2 backward compatible but must use DSMX primary receiver)

[treff]

Grumpy that sounds brilliant and very nice of you. I have never heard of Lemon ( in that context lol) but will have a look, sounds really good.
If you PM me with your address if that's okay and I will pop money to you in the post. Thanks again for the very, very nice offer.

[cjcj1949]

There are really two ratings. The continuous rating is the amount of power the bec will handle and the maximum temperature it will work at. This depends on the ambient temperature and the airflow. The higher temperature you run anything the shorter its life. The burst current is just the maximum rated current. As mentioned the higher the volts the greater the watts as watts is amps X volts drop. Or if in doubt copy a working system. Some manufacturers are a bit on the optimistic side.