Electrics - Lengthen BEC wires

[BluFly]

Hello,

I am in need of some assistance with regard to the lengthening of BEC wires and the best approach.

The instructions to my BEC say that one shouldn’t lengthen the wires but, if you do, to use a thicker gauge wire to avoid voltage drops. I am using a Hercules High Current 5amp BEC in parallel to a Jazz 55-10-32 ESC. The BEC has 2 positive and 2 negative wires as well as 2 power supply cables to the Rx. I believe that the doubles are for redundancy.

I need about 25cm extra in length on the cable, I was planning to use 2.3mm gauge, the BEC wire is about 1.2mm. 2mm bullet connecters are too small for the job. Would larger connectors cause a potential drop? I was thinking of perhaps soldering the wires together rather than using a connector, would this suffice? http://www.stalbansmac.org/yabbfiles/Templates/Forum/default/undecided.gif

All help and suggestions would be greatly appreciated. I have attached a pic for reference.

Thanks,
B

[cptsnoopy]

25cm is quite a large distance. Did you mean 25mm? If you are only increasing the length a few cm then I don't see any problem. I would solder the wires and put heatshrink tubing over the connections. If you need to increase the distance 25cm then I would skip using the main batteries and use a separate rx battery.

[wlfk]

I had a similar problem - annoying isn't it.

I'm a bit of a sceptic about the voltage drop on the voltage-in wires.

Firstly, you're probably operating close to the top end of the voltage rating for that BEC. Say some people operate at 20V but you're operating at 30V (can't remember what the upper limit is) you'll be drawing considerably less current and even with the longer wire you'll still probably be ahead in terms of voltage drop.

Secondly, why couldn't they have used 2 thicker wires. I get why they have two leads on the low-voltage side, but the leads on the HV side probably carry 5 times less current (> 25v versus 5v) but as I recall they're not 5 times longer. It would be far neater.

I don't see voltage drop as being a real issue - so long as you're not drawing too much current and melting the wiring. It might be less efficient but when you're drawing 1 amp (peak) for the servos and 20 amps to fly I don't think a loss of a few % efficiency on the receiver side is significant. Even if you got 10V voltage drop (which you wouldn't) the BEC would still have plenty enough voltage to work with. Given that the low voltage leads are the same thickness as the high voltage leads (correct me if I'm wrong - it's a while since I looked) and the current through them is considerably higher, I think the input leads are way overspecified.

Otherwise a good product that has been working well for me.

K

[Big Fil]

If you can try to only lengthen the input wires to the BEC. It's the output side that is recommended not to lengthen. That being said I did end up lengthening my output side by about 3 inches. Interesting that yours came with two output leads. I just got one a few weeks ago that just had 1.

[BluFly]

Thanks for the quick responses!

cptsnoopy - yep, its 25cm (well, 20 -25). I have attached a pic of where the BEC will sit with the current length. Keep in mind that the location it is situated is where the motor will be mounted.

Big Fil - I am only looking to extend he input wires so that the output wires can reach the Rx where Mikado recommend that this is mounted. The double wires had me stumped as well, had to search a few forums to find out the reasoning behind the move...

So, looks like a direct solder will work for this but will require some careful monitoring to start with.


Still open to more advice!

Cheers, B

[OICU812]

Not a big deal to add to the power side of it at all, I ran wires on the inside bottom of battery tray back to where the BEC would have enough of its wire exiting to make it to the RX. You should not lengthen on the output side ever of any BEC really. Yes they did the dual wire out for redundancy as well for minimal line loss, this was something I seen in their latest versions. Here is a picture of how I had one on my 6003D, you can see that the wires are no where to be seen for power "to the unit". You can see the zip ties yes, I did that to hold the wire to esc male plug firmly against inner side to keep it tidy. And... do make sure even when adding to the input power supply side to use a decent wire such as Deans noodle wire and at least a 14 guage so minimal lose is in play, as well do please note that it is best to mount these BECs label towards the frame actually, not like in my pic. The opposite side needs the cooling more so as that is where the heat will build.. :D

[Big Fil]

Wow, now i'm kinda bummed that I didn't get the dual output one. Only bought mine about 3 weeks ago from RH.

[OICU812]

Single is fine, there is really not a whack of diff, only if you are hammering it and using super high amp draw servos would ya ever even know, don't be to bummed, the bum don't need more abuse :D

[Big Fil]

I know it will work fine. The one in my dad's 600 has been flawless. It's more the fact that you buy something at full price to find it was already the old version.

[itsparks]

BluFly (http://www.helifreak.com/member.php?u=44130), is that the stock Spektrum servos you have installed on the tail ?

[jamesotron99]

BluFly (http://www.helifreak.com/member.php?u=44130), is that the stock Spektrum servos you have installed on the tail ?

Looks like it. If you really value your machine you should put in servos that aren't going to have their shafts shear in flight.

Good luck!

[itsparks]

Looks like it. If you really value your machine you should put in servos that aren't going to have their shafts shear in flight.

Good luck!

Id also put in a High speed digital one.