General The best way to wire up.

[concodd]

Have finished the build on my Sab 700, now time to get down to the electronic side of things. I keep looking at these 2 large lipo's and the ESC and wonder which is the best way to wire up the three allowing for space to put the canopy on. should the main wires for both Lipo's oppose each other with the main leads on the bottom and be joined with the Esc under the Heli and then strapped up, or have you guys done it a different way out there??

 

[pvolcko]

I usually create stick packs by putting them leads end to butt end, create or purchase some extensions for the rear battery, put them on, then wrap it all in some large heat shrink tube so you end up with the main leads and balance leads coming out at the front of the front battery. Then solder on two connectors to the ESC out the front (trimming the esc leads down a little bit if there is too much wire to be useful). I'll also solder on a set of leads to power the BEC.

Can't do it right now, but will post some pics up later on in the day to show what I'm talking about.

 

[concodd]

Sorry Paul, my internet was down. Thanks for the tip and look forward to the picture.

 

[Derek]

I'd be curious to learn about this, too! I'm looking for a better way to setup my wires for my 600e.

 

[pvolcko]

Oy, sorry. I was out all day today. I'll do this Sunday evening when I get home (have another full day planned).

 

[pvolcko]

Sorry for the delay.

First up the ESC wiring. This is on a 700 TRex. 120A HV CC ESC. In this case the ESC is a bit away from the battery area (I run the pack plugs out the back), so the full stock length on the ESC leads was kept. I used EC5s for the pack connectors. The BEC lead is the pair of wires "tacked" onto the two main leads feeding the ESC. I cut a small square of insulation off the main ESC feeds, then soldered the BEC feed lines onto it. You have to make sure you heat up the main lines enough so the solder will flow into them at this connection point. If you just solder a blob onto the outside strands it will not be a secure connection and it may not be able to feed the current you need for the BEC reliably. I used a generous amount of shrink tubing extending beyond the solder point, along with a generous amount of extra BEC feed wire at the rear, to make sure the solder joints aren't strained. I also used a slightly over gauge wire for the BEC feed since it is on the long side and I didn't want resistance to be an issue. Note the smaller connector in-line on the BEC feed wires toward the front. I used an EC2 connector here. I highly recommend using such an inline plug that way you can power the BEC from a small 2S lipo while working on the bench, without risk of the ESC and main motor powering up.






The battery packs: As I mentioned, I make stick packs. This isn't necessary, especially when using a slide in tray system as the TRex employs, but it makes things cleaner and provides some protection for the extender connections. In the case of the G700, if you are not utilizing an aftermarket tray system, such as the KDE offering, then making them into a stick pack can be very useful. Some battery makers also offer stick pack configurations out of the box, such as Pulse, in which case all you'll have to do is solder on the main power connectors you want and then go to town.





Here's a view of the out the front wiring on my G700. The prior owner used Anderson Power Pole connectors. Luckily instead of crimping the series connection pair directly onto the main leads he utilized a plug on series harness, so I was able to cut his connectors off the hardness and put on the EC5s which I prefer and use in all my 500+ size helis. Eventually I will cut off the power pole connectors and splice the EC5 segment of the harness to cut down on the bulk of wires out the front. However, this all fits inside the canopy without issue.



Here is a pic of the underside of my G500. The G700 has the same kind of wiring and mounting scheme for the BEC and ESC. This one I built from scratch, though, so it has my usual wiring pattern. BEC leads tacked into the main ESC leads, EC2 in the middle between the main tap and the BEC for bench powering the BEC and Rx/servos. The extra red plug connector next to the ESC throttle line is the RPM sensor feeding into the Ikon for governor control.



If you want any more detailed photos or wiring diagram or anything let me know. Hopefully that gave you some ideas.

 

[Derek]

Thanks for this, Paul! It has even helped me out, too. I haven't even touched my 600 in quite some time due to the crumby weather and my work schedule. However, I'm hoping to get working on it again real soon and I remember having some issues with mounting the batteries.

When locating the CG on these bigger heli's, it's probably a lot of trial and error, isn't it? Mount the batteries to the battery tray, slide in the tray, add the canopy and check the CG. Then remove the canopy, remove the battery tray and move the batteries as needed, then repeat. Right?

 

[Tony]

That is correct on the CoG Derek. Once you have it though, you have it.

 

[concodd]

Thanks Paul, the pictures are a great help.

 

[pvolcko]

On CoG I usually strap the batteries to the tray without any velcro between the batts and the tray, that way they slide with just a bit of pressure. Slide in a tray with batts, lift heli, put down, slide batts as needed, repeat until I get it just a hair tail heavy, then put on the canopy and hopefully it is balanced. If not I usually tap the batts forward just a smidge to balance it out fully. Take the batts and tray out, being careful not to move them on the tray.

If two unbundled packs on the tray then: unstrap just one, velcro it in place hard against the other battery, strap that one down, remove the other and velcro it down.

If a stick pack: put a mark on the pack and the tray for alignment, remove the pack and velcro it, aligning the marks again, then strap it down.

Should be all good. Little bit of trial and error, but not too bad. I imagine getting CoG right on an airplane is far more difficult.