Trying to decide whether to use BEC or a receiver battery on the Sig Astro Hog I'm building. The ESC in question is a CC ICE 75A with a 5A switching BEC. I'd like to use the BEC for the obvious reasons, weight savings, one less thing to have to charge and of course the cost. If I go with RX battery I'd need to purchase a RX pack since the ones I have are several years old and I'd like to go up to a 5 cell pack. I'd also have to get a new switch harness because I don't trust the ones I have in my box of parts.

How many of you use the BEC on a larger model like this?


Mike

Originally Posted by MikeCr

Trying to decide whether to use BEC or a receiver battery on the Sig Astro Hog I'm building. The ESC in question is a CC ICE 75A with a 5A switching BEC. I'd like to use the BEC for the obvious reasons, weight savings, one less thing to have to charge and of course the cost. If I go with RX battery I'd need to purchase a RX pack since the ones I have are several years old and I'd like to go up to a 5 cell pack. I'd also have to get a new switch harness because I don't trust the ones I have in my box of parts.

How many of you use the BEC on a larger model like this?


Mike

I'd happily use a built in BEC on something that size, especially from a reputable brand. If you're worried, just use on e of these as well: http://www.scorpionsystem.com/catalo..._Backup_Guard/ It only cuts in if your BEC power supply has a problem, and it's small and light.

The other solution I like is an external switching BEC like this one: http://www.arrowindhobby.com/hobby/e...ccessories.asp powered by a little 2S 800mAh LiPo. 3 8 minute flights on a 50e pattern model sees the pack still at about 90%. The battery already had JST plug and so does the UBEC - plug and play!

I use BEC's on all of my electrics (3 to 6 cell .46 to .60 sized equivalents). Never had a problem.

Kurt

Thanks guys. That little backup guard is a neat little device and cheaper than a RX pack and switch. That particular UBEC.though wouldn't work in my case as I'll be using a 6S. But I know there are others out there that would handle 6S.

I don't know, maybe I'm just being paranoid. I don't remember ever having a BEC fail on any of my models in all the years I've been flying electrics even going back to the brushed motor days.


Mike

I use a BEC on all my models, but on my larger models it's always a stand-alone one, not the one built into the ESC.

Originally Posted by abenn

I use a BEC on all my models, but on my larger models it's always a stand-alone one, not the one built into the ESC.

Why is that?


Mike

My decision point is whether the model is sufficient to carry two power sources. QED.

With regard to having separate BEC to the ESC but of same power source .... IMHO unless ESC is unable to carry the number or power demand of servos, ESC is opto - it's a useless exercise. You are not reducing risk of failure in any way at all. In fact I reckon you are increasing it - by introducing an extra connection / link in the system.

If you were to carry a separate power supply for Rx via BEC or NiMH pack etc. - then that is best way and understandable.

With NiMH packs now higher capacity and smaller than before ... this opens up many more models to carry separate Rx supply.

Nigel

Originally Posted by solentlife

My decision point is whether the model is sufficient to carry two power sources. QED.

With regard to having separate BEC to the ESC but of same power source .... IMHO unless ESC is unable to carry the number or power demand of servos, ESC is opto - it's a useless exercise. You are not reducing risk of failure in any way at all. In fact I reckon you are increasing it - by introducing an extra connection / link in the system.

If you were to carry a separate power supply for Rx via BEC or NiMH pack etc. - then that is best way and understandable.

With NiMH packs now higher capacity and smaller than before ... this opens up many more models to carry separate Rx supply.

Nigel

Weight isn't much of an issue, AUW will probably be in the 7.5lb range. And as you said it doesn't make much sense to use a separate BEC with or without a separate battery for it unless the ESC's BEC can't handle the current. In my case the ICE's BEC is 5A and is also adjustable from 5 to 7 volts.

On my Century Swift helicopter (6 pounds) I use a separate RX battery although that's more about being able to isolate the radio power from motor power when adjusting pitch curves. It's a pain to remove the pinion gear and the motor wires are soldered to the ESC because of physical reasons.

I feel more comfortable with a separate RX battery on a model this size. And I suppose now is not the time to go cheap on it when I just spent $500 on a generator to charge the thing at the field. OTOH that could be used as an argument to use the BEC, I just spent $500 on a generator to charge the thing at the field!


Mike

On my Century Swift helicopter (6 pounds) I use a separate RX battery although that's more about being able to isolate the radio power from motor power when adjusting pitch curves. It's a pain to remove the pinion gear and the motor wires are soldered to the ESC because of physical reasons. ....

There's a much lighter simpler answer for that one ..........

Remove Rx battery ... plug in BEC from ESC via a standard switch harness to a Y lead into Rx. The standard harness when switched to Charge - isolates the BEC .... You then plug in external power to other Y lead connection to power Rx ... the harness stops power getting back to ESC BEC.

You've now lightened your model. But still have safety factor.

Just a thought ...

Nigel

I use a BEC on all my models, but on my larger models it's always a stand-alone one, not the one built into the ESC.

Originally Posted by MikeCr

Why is that?


Mike

It started out being because I didn't think the built-in BECs were up to it. But the other reason is that I feel the chance of damaging an ESC, and consequential collateral damage to the built-in BEC, is perhaps higher than the risk of damaging a stand-alone BEC.

Now that some ESCs have massive BECs built in (e.g. CC's new Talon 90) it's arguable that there's no need for stand-alone BECs. But I'm still paranoid, so I think I'll stick with the stand-alones.

BTW, I don't use Rx batteries because they're something else that needs charging and looking after. They (and their associated on/off switch) can fail too, though I don't know what the statistics are compared with BEC failures.

Originally Posted by abenn

It started out being because I didn't think the built-in BECs were up to it. But the other reason is that I feel the chance of damaging an ESC, and consequential collateral damage to the built-in BEC, is perhaps higher than the risk of damaging a stand-alone BEC.

Now that some ESCs have massive BECs built in (e.g. CC's new Talon 90) it's arguable that there's no need for stand-alone BECs. But I'm still paranoid, so I think I'll stick with the stand-alones.

BTW, I don't use Rx batteries because they're something else that needs charging and looking after. They (and their associated on/off switch) can fail too, though I don't know what the statistics are compared with BEC failures.

Funny thing is - I've had more stand-alone BEC failures than anything else !

Rx battery packs - which were the norm for all models not so long ago - I only can remember 1 instant for me ... a factory soldered pack let go.

ESC BEC's ... cannot remember any failing on me ... no brown-outs .. nothing.

My worst fails have been stand-alone BEC's ... and not one was outside its stated design parameters. Two the leads just fell apart from the boards ... another just fried for no reasion at all ... another just has intermittent fault ... That's 4 in 1 year ........... out of 5 installed. Given I've been in this for nigh on 45yrs with only 1 Rx pack failure ............ that's not a good record for BEC's !

Nigel

Originally Posted by solentlife

Funny thing is - I've had more stand-alone BEC failures than anything else !

Rx battery packs - which were the norm for all models not so long ago - I only can remember 1 instant for me ... a factory soldered pack let go.

ESC BEC's ... cannot remember any failing on me ... no brown-outs .. nothing.

My worst fails have been stand-alone BEC's ... and not one was outside its stated design parameters. Two the leads just fell apart from the boards ... another just fried for no reasion at all ... another just has intermittent fault ... That's 4 in 1 year ........... out of 5 installed. Given I've been in this for nigh on 45yrs with only 1 Rx pack failure ............ that's not a good record for BEC's !

Nigel

Oh dear! That's not helping my paranoia one little bit

In the old days when I flew glow, and at the beginning of my electric days when I was on 35MHz, I used standard 4-cell Rx packs and never had a failure in flight. But I've read of a few, including on/off switch failures, "black wire corrosion" failure, and simple old-age cell failure.

Since I went to 2.4GHz I replaced all my Rx packs with stand-alone BECs, purely for convenience. In about 5 years of flying with them, I've never had a failure yet, nor have I read about any until yours. Mine are Kool Ultimate BEC, Hyperion Cool BEC, and CC 10A BEC.

Thanks for all the info guys. I too have had very good experiences with RX packs and switches but then I always kept an eye on them. I never used a battery pack for more than maybe 4 or 5 years before replacing it, usually retiring it to some non RC application before disposing of it. Same thing with the switches.

That being said while I was out this morning picking up some other goodies, RC related and other, I bought a 5 cell NiMH 2000mAH pack and a new switch harness. I figure with the type of plane this is a full charge should last all day. Plus I will have a digital voltage monitor on the plane so I can tell at a glance if my battery is getting marginal. I've got a neat little monitor on my Century Swift heli that has a flashing green light that indicates all is well. It goes to solid on when the battery is getting low.


Mike

Originally Posted by MikeCr

.......That being said while I was out this morning picking up some other goodies, RC related and other, I bought a 5 cell NiMH 2000mAH pack and a new switch harness. I figure with the type of plane this is a full charge should last all day. .....Mike

Wasn't so long ago - we were flying all day with 500mAh Rx packs ... all weekend with 1200mAh ... Some of us had Field chargers as well ... but rarely used them.

I have a dinky little 4.8v 250mAh NiMH pack that I use in weight sensitive stuff ... made up of 1/2 size AAA's ........ magic little pack. Came out of a Supermarket 2ch toy ...
Bunch of 4.8v NiMH 2300mAh packs I made up from over counter AA's in holders - all taped up secure to prevent any cell movement ...
All proving excellent.


Nigel

Originally Posted by MikeCr

Thanks for all the info guys. I too have had very good experiences with RX packs and switches but then I always kept an eye on them. I never used a battery pack for more than maybe 4 or 5 years before replacing it, usually retiring it to some non RC application before disposing of it. Same thing with the switches.

That being said while I was out this morning picking up some other goodies, RC related and other, I bought a 5 cell NiMH 2000mAH pack and a new switch harness. I figure with the type of plane this is a full charge should last all day. Plus I will have a digital voltage monitor on the plane so I can tell at a glance if my battery is getting marginal. I've got a neat little monitor on my Century Swift heli that has a flashing green light that indicates all is well. It goes to solid on when the battery is getting low.

Mike

I've been surprised by just how little power my servos use. I have 4 digital minis (2 x elevator, 2 x aileron) and 1 digital standard (rudder) in a 1.6m span 3kg pattern model. 25 minutes flying pulls less than 200mAh out of a 2S 800mAh LiPo. I got similar results with a 48" 3D model, with 4 servos. At the size and weight of the pack and the standalone UBEC, I'm pretty happy