Just some quick information on the MM esc

[redhatman]

Hey guys, I was asking CC about using the MM esc with over 12 cells, heres what he said...

He said, 12 cells and 3s is the max because of the amperage that you are wanting to draw. Since the more amperage, gets more heat there is danger. It is 100A and the other limit. It does have a thermal shutdown, but sometimes it is too late. He said that the actual voltage limit (100 amps for other limit) was 22 volts on the FET's. Obviously, you cant hook up a 7XL with a 22 volt setup, because that would cause way to many RPMS, which in turn would heat up VERY fast, and could easily fry the whole system.

All in all, anything over 3s and 12 cells voids the warranty but it doesnt mean that it cant handle it. He said the ESC itself is very strong, but when the motor isnt happy, it can ruin the whole system.

Guys run 4s through them with a ubec and disabling the mm's bec. You could get away with 14 cells by doing the same. But it would be so heavy it would only be good for speed runs.

redhatman,

Welcome to the forums.

The information that you got from Castle is the stuff that they disseminate to the general public. If you call them, off the record so to speak, the information changes.

The real reason that there is a 3S limit on the MM is because of the internal bec, which can only handle 3S (and not very well). If you go with an external bec, the mm will comfortably handle 4S and some will even do 5S.

Yes, the MM will "only" handle 100A constant, but will also handle much more in surges. I have five MM escs and only one of them has ever been run on anything less than 4S lipo.

[BrianG]

And if you are running a 4s or 12-14 cell setup, you can choose a motor with a higher wind so you aren't pulling too much current. If a motor was pulling 100A at an even 15v, that's 1,500 watts! I highly doubt anyone here is drawing that much power continuously! A 10Ah battery would only last 6 minutes if that were the case.

And the Quark rates their ESC at 125A continuous, and it uses the same FETs and same number of them. So, there's no reason why the MM can't (other than maybe PCB trace limitations).

Castle's statement is to cover their butt. They know people are going to push the spec'd limits so they apparently incorporate a bit of derating with this in mind.

And about the BEC: IMO, until all ESC makers incorporate switching BECs in their ESCs, they should design a very simple circuit that automatically disables the internal BEC if it sees over 9v.

Have any of you guys tried a 5S pack with a MM? That would bump me just a little to keep me in the same speed range I am now with the IBs and the 18/38 gearing I'm presently at. I guess I could use a 4S if it's safer for the system and go to my 20/36 gearing and maintain the same approx. top end. I have no shortage of torq right now.

I'm thinking it's about time to start making the lipo switch.

[Serum]

yeah, several have done it.

Originally Posted by Serum

yeah, several have done it.

That would be cool, it would cut my battery weight almost in half and boost me 1.7 volts, not to mention the increased run time. The 4S would more than cut the weight in half. I think that's going to be the answer to being certain I can run an entire 20 min MT main at the local track.

How much do you think the extra 1.7v will raise my motor/ESC temps over my current (14)IB set up? I'm kind of leaning toward the 4s just for the safety factor to avoid overheating. I can gear it back to the same speed I have now.

[Serum]

Welcome to the lightweight world of lipo..

The big deal with lipo is really the increased voltage of the packs, it is more the increased voltage under load. Even the best nimh cells drop significant voltage when hit with a load much over 35A. Yes, they might be able to hold around 1.1v per cell at around a 100A draw, but will drop voltage significantly after about 10 seconds.

A good lipo cell will hold 3.5v under a 100A load. I know it's comparing apples and oranges, but in the end, the lipo will be better. You should also see a good boost in overall performance over the charge of the battery pack.

I have run a couple of my MMs on 5S. They do OK, but I'd stick with 4S. The MMs will very comfortably handle 4S.

Originally Posted by AAngel

The big deal with lipo is really the increased voltage of the packs, it is more the increased voltage under load. Even the best nimh cells drop significant voltage when hit with a load much over 35A. Yes, they might be able to hold around 1.1v per cell at around a 100A draw, but will drop voltage significantly after about 10 seconds.

A good lipo cell will hold 3.5v under a 100A load. I know it's comparing apples and oranges, but in the end, the lipo will be better. You should also see a good boost in overall performance over the charge of the battery pack.

I have run a couple of my MMs on 5S. They do OK, but I'd stick with 4S. The MMs will very comfortably handle 4S.

Thanks, good to know. I think I'm going to stick with the 4S.

[crazyjr]

I have run mine on 5s, but they were older ones and i'm not sure the newer ones will handle it