6s on M Monster
 

I'm converting a losi 8ight T 2.0 and I plan on running 6s. My question is, does the bec have to work harder with higher voltages, will I have a higher likely hood of damaging the esc on higher voltage. Would it help if I run a bec? I already have the CC bec

Actually, most switching BECs (which is what the MMM has) tend to work more efficiently with higher voltage because of the reduced current needed. And, there is less chance in saturating the main switching coil with lower currents.

However, a linear BEC (which is what the MM has) gets less and less efficient as input voltage climbs. This type should only be used with 2s lipo max, otherwise, disable it (remove the red wire) and use an external switching BEC.

BTW: Welcome to the forums!

Since I've sold all my nitro stuff, I still have a nice jr9100s HV servo laying around, this is the all aluminum case with .06 speed and 230oz of torque. I was planning to use it but with only 6 volts coming from the bec it's specs drop down to the normal 9100 180/.06. If I install the CCbec so I can boost the voltage going to the servo, will there be any pros or cons using it instead of the built in bec on the monster? If I do go with the cc bec, is the installation the same as with the MM, just remove the middle wire comming from the esc?

The external CC BEC most likely has more current rating, and is voltage programmable, so it should have no trouble powering the servo. The downside is the extra wiring required. And yes, just remove the red wire from the ESC.

Keep in mind that removing the red wire from the ESC throttle cable will make programming the ESC more difficult. If the red wire is permanently removed, the only way to program the ESC would be to power it up with at least 2s lipo/6 cells while the Castle Link is hooked up. Options to get around this limitation:

- Make it so the red wire can be re-inserted easily.

- Use a short servo extension with the red wire removed. This would leave the ESC cable unmodified.

I have been told by Pat that the higher voltages do work the DC-DC unit harder because of the higher switching rates.


I say don't give it a worry.

so are you saying it's better witht the cc bec or worst??

You would put the servo load on the CC BEC, and I can't comment what is better. I would not use an external BEC personally, as my MMM have been running fine.

ok....of course if you are using the ccbec the load is going to be on it and not the esc??? From my understanding, the ccbec is basically the same thing in the Mmonster except it handles more amps and has adjustable voltage. I guess my question should have just asked if there was any difference between the two as far as one being more efficient or reliable. Also I own 3 MMonster controllers and havent had a problem with any of them, but I also have only previously rand 4 or 5 cells. The 3 locally that I have seen problems with, 2 of them were on 6s and the the third was on 3s. If I can prevent burning up the bec on the MMonster by using the CCbec then why not, expecially if I already have it? Worst case the CCbec fails and I just plug the red wire back in and run the built in bec. Well there could be worst but I'm not going there.

Can you define "working harder" because from my testing, it appears that for a given load, higher input voltages (to a degree) yields highest efficiency.

Yes, it yields higher efficiency, but it's harder on the parts due to higher partial currents -- even though the average current is lower, the I^2R losses are higher in the FETs.

Since both are switching BECs, I would expect either to be comparable efficiency-wise. If your goal is simply higher voltage to get the most out of your servo, then the CC BEC is gonna be the desired option. If you are worried about the CCBEC possibly failing (which generally means it will either output 0v or full battery voltage), then you could wire the system up so that the CCBEC only powers the servo, but the receiver and any other servos run directly off the ESC's BEC.

lol, straight from the horse's mouth! :smile:

Thanks for that info. Makes sense. So, the FETs work harder because of the higher partial currents, but does the coil or diode (assuming it's not running into saturation) work any harder?

Yes, both do -- the diode recirculates longer, and the peak currents are higher in the coil. Capacitor currents are higher too, but they don't even get slightly warm...

So even though they work harder, efficiency increases? Does this bump up output as the voltage increases, or does it decrease from the possibility of extra heat?

When testing different BECs, it seems the coil is the hottest part at any load and input voltage, so that makes sense. The only BEC I've ever tested where heat is more distributed is the Western Robotics HV; but that uses a very large/robust coil so it probably has enough mass to absorb it better.

It's an interesting problem. We are using a flat wire wound coil in our BECs (where the coil is wound like a slinky), which give VERY high saturation currents, but only so-so RMS current values. Flat wound toroids are just now starting to hit the scene, which give even higher saturation currents, lower noise, and higher RMS currents. But they are tall -- which doesn't fit well into RC applications. But every year, we see higher and higher currents in smaller coils. I would have thought that coil technology would have peaked 20 years ago -- but they keep getting better densities.


--- And BTW, sorry to jack the thread for a technical discussion

Gotta remember people weren't really concerned about small size/light weight 20 years ago. These days, everyone wants their entire world to fit in their pocket, so naturally, that demand requires more advances.

And, techy thread jacking is the norm here. At least it is related to the discussion (if a tad remotely).

this actually sounds ideal, is there a easy way to do this?

Use a Y harness that routes power from BEC to servo, and the extra lead goes to RX and passes only signal wire.

so I would need to remove the signal wire from the cc bec (orange) and only have the orange wire on the other side of the y harness? Leaving all the wires from the esc intact and plugged in normally? Or just hook up the black and red wire from the bec to the black and red to the servo and just plug the signal directly back into the reciever? Does the signal wire from the CC bec have to be plugged to something?

Just remove the red and black (or just one) that go from servo to RX. No need to remove signal from the external BEC. No need to do anything else.

thanks!