Mamba Max and 3s

[jacobsjo87]

Does the Mamba Max need a CCBEC on 3s lipo?

[Unsullied_Spy]

No, it works just fine on 3s without any modifications.

[magman]

True that it doesn't need it, however, if you do decide to use a ccbec, it will help lower temps. I run 3s on my mm in my crt.5 w/a ccbec

[jsr]

It's been a little while since I had the MM, but I think it uses a linear BEC, which means all excess voltage is converted into heat. On 3s, that's about 11.1V (usually higher). If your devices (servos, RX) are drawing say 3A, that's 33.3W of power that the ESC has to dissipate in the form of heat. And the MM is a very small ESC that does not handle excess heat well. I'd recommend an externel switching BEC (doesn't have to be CCBEC).

[BrianG]

You're right about it being linear, but the wasted power figure is a bit off. The BEC has to dissipate the differential voltage times the current. So, for a BEC value of 6v and 3s lipo (11.1v) and 3A load, the wasted power would be 15.3w. Either way, on anything over 2s and 1A load, they are too inefficient. Which is why I recommed a UBEC on anything above 2s lipo or 7 NiMH cells.

[J57ltr]

An efficiency of 54%? That sounds about right, but how did you come up with that figure? 33 watts is a lot to get rid of.

Jeff

[jsr]

I'm sorry, Brian's right. I didn't calculate correctly. The wasted power is the input voltagfe minus the output voltage times current. Still a lot of heat that you don't want the tiny MM to try to get rid of.

[Unsullied_Spy]

I'd say it depends on what you run it in. I run 3s in my Rustler all the time and the MM has no problem handling it. After 30 minutes or so the ESC is hot (haven't checked the temp, but it felt like 170-180) but it works just fine. I guess I'm too lazy to wire in an external BEC to something which is totally capable, rated, and warranteed to handle what I'm putting it through. In something heavier like a CRT .5 it would be a good idea because you'll be working the ESC much harder than my feather-light Rustler.

[BrianG]

Don't forget that the BEC on the MM is not even close to the heatsink; it's on the brains board. Small vehicles put about a 250mA average current draw on the BEC (sometimes lower, sometimes higher), which still puts power dissipation 1.275w, which is still quite high for such a small unheatsinked area. I did some testing a while back and measured temps with a low load and you'd be surprised how fast and hot it gets. It runs, just not the best.