BEC or battery?

[flymustangs]

I just received the shipping notification from RH for my Xxtreme kit

I think I have everything sorted out and have all the parts on hand except the BEC or receiver battery decision.

I know this one is as old as the nitro versus electric debate, but would like to get a fresh perspective on it with the Xxtreme. I've done it both ways, usually using a BEC for smaller helis and a battery for larger helis.

The pluses to me for the battery is a neater setup and potentially higher current available. The pluses for the BEC are no need to charge a different battery or keep track of how much capacity is left.

It seems that plank guys go to extremes to set up redundancy for the larger planes. I'm guilty of this as well. On a 50cc IMAC plane I have two A123 batteries feeding a Duralite Baselog. This doesn't seem to be the case for helis, even large ones like the Xxtreme. I guess some of the scale and turbine guys do this just due to the shear expense of these helis.

I guess the new version of the WR BEC would give the best of both worlds.

Any thoughts would be appreciated.

[Big Fil]

I personally am using a WR super BEC. Thought about using a seperate pack but for me I wanted to keep the routine the same amongst my fleet. I'm sure at some point i'd forget to charge a seperate pack as it's another thing to monitor. That's just for my situation and knowing my likes and tendancies. I'm sure if I had always used seperate packs it wouldn't be a big deal since it would be part of the regular routine.

As for redundancy, if you go the BEC route you can always use a buffer pack that is constantly kept charged.

Oh yeah, the other thing I did different on this bird was to wire the BEC to operate off one of the 7S flight packs. The thought here is that the BEC is not having to do as much work to step the voltage down from 29v as it would be from 58v. WR underrates there their stuff so i'm sure it's not an issue across the full voltage, but I figured i try it out and see how it goes.

[Big Fil]

Just saw this in another thread today. Looks like another option. I like how it has the ability to run HV to the cyclics and LV to the tail.

https://www.helifreak.com/showthread.php?t=389686

[AusAnt]

I'm going to hedge my bets. I have a WR superBEC with 7.4V output, and I'm going to install a small 2s (1300) pack which I will charge to 7.4V then install and never take it out, so it acts as a buffer and/or short term power in case of a BEC or main pack failure. I am planning to put one WR supply in Sbus Rx and one in VBar, and do the same with the 2s pack.

[flymustangs]

Originally Posted by Big Fil

Oh yeah, the other thing I did different on this bird was to wire the BEC to operate off one of the 7S flight packs. The thought here is that the BEC is not having to do as much work to step the voltage down from 29v as it would be from 58v. WR underrates there their stuff so i'm sure it's not an issue across the full voltage, but I figured i try it out and see how it goes.

I see that you maidened this weekend. Congrats!

Any data on this setup? Have you seen any appreciable difference in the mah put back in the packs?

[Johnda]

Originally Posted by AusAnt

I'm going to hedge my bets. I have a WR superBEC with 7.4V output, and I'm going to install a small 2s (1300) pack which I will charge to 7.4V then install and never take it out, so it acts as a buffer and/or short term power in case of a BEC or main pack failure. I am planning to put one WR supply in Sbus Rx and one in VBar, and do the same with the 2s pack.

Haven’t WR said that their BEC’s shouldn’t be used with a buffer pack? They’re due to release another device that can accommodate a buffer pack from what I understand

[Big Fil]

Originally Posted by flymustangs

I see that you maidened this weekend. Congrats!

Any data on this setup? Have you seen any appreciable difference in the mah put back in the packs?

With a limited amount of flights this weekend and a new charger that stopped a couple of times mid charge, I can't quite say yet. Hopefully by this weekend i'll have a better idea.

[Laughingstill]

I used a 2s lipo with HV servos. I used a total of 206 MAH in two 5 minute flights If you have a buffer pack with a BEC, you will never know if the BEC fails until the buffer pack is depleted and then you know what happens next. I chose to have one less failure point to go with and the weight of a 2s lipo on an 800mm machine is negligible..........Ron

[AusAnt]

That's good info Ron - I was struggling to work out how much current we actually draw on a setup like this. What brand of servos are you running?

If my math is correct, 206mah in 10 min = 1236mah in 1 hour which equates to an average current of 1.236A. So even being conservative and doubling or tripling that average draw, we're still inside 5A average, and because a WR BEC can take 10A cont and 15A peaks, there's a safety factor of around 12 times the average amp draw to allow for some big peaks. Sounds like it should be plenty. I was thinking amp draw was going to be higher than that.

I hadn't heard that about the WR not being suited to a buffer pack - I'll check that out too. I remember Dave Dahl (I think) saying the same thing about not knowing if your BEC has died, and he said the best way to deal is always leave the switch on the buffer pack off, connect the flight pack so the BEC initializes the equipment. Then you know that your BEC is working, then turn on the switch for the buffer pack. That way, the longest you could possibly fly with a failed BEC would be 1 flight, and as long as your pack has capacity for that you're OK.

I was thinking of other failures like I have heard of people's main battery connectors having a bad solder joint and coming loose etc, which would kill motor and BEC. I just thought some redundancy would add some safety. Anyhow, I'll look into the WR thing and maybe I won't worry about the separate pack.

Thanks for the info.

Ant

[belgoheli]

I´ve never used an external BEC (spoiled by Kontronik of course) but I have bought a WR Hercules for my XXtreme.
Hence my stupid query: where to connect the leads of the Bec? I mean do I have to solder additional connectors to the 14s Lipo´s or additional connectors to the ESC? For me this is not clear from the sketch in the WR manual.

Thanks

Belgo

[Laughingstill]

I am running BLS 157HV and a BLS 256HV.

Belgoheli:

If it is a Super mini (14s capable) the solder the leads to the main leads of the ESC input. If it is a Mini (12s) then solder the leads to ONE of the battery leads (One the (+) of one battery lead to the ESC and the (-) of the SAME battery in the series cable)

[Big Fil]

If you need to go across one set of batteries due to the BEC not being rated for 14s, make sure to wire it correctly across the battery connector of pack one. Pack one is the battery that shares a direct connection with negative side of the ESC. Doing it across the connector to pack two will fry your electronics as the full voltage from pack one will bypass the BEC. Ask me how I know this

This Diagram shows the correct way using less than a 14s BEC




If your HV BEC can handle the full 14s then it can be wired like this




Note in these diagrams they are using 6s packs. For our purposes on the Xxtreme assume 7s packs.

[belgoheli]

All clear

Many thanks guys

Belgo

[desertstalker]

Ill mention it here because someone on the SAB forum fried a VBar, make sure if you are using only one pack in a pair to connect the black lead on the BEC to the SAME place as the black to the ESC.

Using the other pack instead will pump ~30V through you electronics and out through your ESC, may well kill everything.

[flymustangs]

WR said it would be two weeks to get a modified Super BEC. I guess that was the push off the fence I needed. I've decided to go with a Lipo receiver pack and a basic lipo monitor. I've used receiver packs before so I'm used to that scenario and the lipo monitor will give a bit of insurance.

[Nko15]

I'll never look back since i started using a Gryphon Quasar bec. adjustable output, up to 75v input, 10/20A rating.

[Euwan]

Just wondering the two power leads for the wr bec what slots on the vbar should they be plugged into. I will be plugging the TM1000 on slot four of the vbar will there be space?

[Magneto]

You cannot use a small lipo with the WR bec or any bec for that matter, WR is coming out with a redundant module for a small lipo to be used as back up, I think alot of folks get confused because Kontronic has the ability to use a nicad on the bec. I am running my WR super herc off both 7s packs @58v the same setup as the Dahls are using.

[heli21]

I'm using a Thunder Power G6 Lite 2s 2700mAh battery... working great!

Rob

[macpass]

Originally Posted by heli21

I'm using a Thunder Power G6 Lite 2s 2700mAh battery... working great!

Rob

So no BEC at all? How do you get power from the lipo to the VBar? Did you just make up an adapter and do you have the 2 power inputs as recomended in the manual? A picture would be much appreciated as I'd like to run a similar setup but coming from big nitro / different helis I'm not sure what goes on here. Cheers!