evx

[tyrewq]

manual on evx sez:

"12 CELLS ONLY! Two, 6-cell battery packs in your E-Maxx are connected
in series which provides 14.4 volts to the electronic system. Never use
fewer or more than 12 cells (14.4V). This will damage the EVX speed
control."

but i wanna use only 7 cells. anybody tried that before? i understand overvoltage will damage system by burning wires/capacitors up but i never heard of esc being damaged by undervoltage?

[BrianG]

They are probably saying that to keep people from using a really fast (high kv) motor, which will pull much more current than it is rated for. For the same power, there is MUCH less current with 12 cells than only 7 cells.

[tyrewq]

Originally Posted by BrianG

They are probably saying that to keep people from using a really fast (high kv) motor, which will pull much more current than it is rated for. For the same power, there is MUCH less current with 12 cells than only 7 cells.

when you said "high kv" are you referring only to brushless motor? i'm just using plain dual 540 motors(stock mabuchi motors 27 turns). don't know how to convert turns to kv. is 7 cells on evx ok on this setup?

[BrianG]

Oops, yeah, I was thinking about brushless motors. But really, the same holds true for brushed motors.

[tyrewq]

thanks!
another question, does evx have lipo cutoff? i just noticed that other novak esc does like the rooster reversible.

[Patrick]

No, it doesn't have lipo cutoff, I'm not sure if lipo's would have been around (in rc anyway) when the evx came out.
If you want it to go slower, I've heard of people wiring the motors in series instead of parralel, to add the resistance (double) and theoretically halve the current draw (double runtime) and half the power.
I've never tried this (I'm always trying to go faster not slower:027: ) and I've never seen it done, but there should be some threads around here about it if you do a search.

I think he was talking about using 2 7 cell packs.

[BrianG]

Originally Posted by Patrick

If you want it to go slower, I've heard of people wiring the motors in series instead of parralel, to add the resistance (double) and theoretically halve the current draw (double runtime) and half the power.

Actually, you almost got it right. Half the current, but 1/4 the power. ;) Just think of the runtime!

[Patrick]

Originally Posted by bensf

I think he was talking about using 2 7 cell packs.

I still think he's talking about 1 7 cell pack, because he's worried about the evx being damaged by under voltage.

Originally Posted by BrianG

Actually, you almost got it right. Half the current, but 1/4 the power. ;) Just think of the runtime!

Yeah, I think I remember reading it was 1/4 the power now that you mention it, but I don't really understand how that works, if you half the current and get a quarter of the power where does the other quarter go? Or do you mean half the current though each motor and a quarter of the current all up?
The runtime would be pretty good, but that's what 8000mah lipo's are for:027:

[BrianG]

Originally Posted by Patrick

...Yeah, I think I remember reading it was 1/4 the power now that you mention it, but I don't really understand how that works, if you half the current and get a quarter of the power where does the other quarter go? Or do you mean half the current though each motor and a quarter of the current all up?

Well, it's because you are changing the motors from parallel to series. The resistance is changing by a factor of 4.
So, just to make up some easy numbers, let's say each motor has 10 ohms. In parallel, that's 5 ohms. With 20v (again, some easy arbitrary number), that's 4A for 80W.
Now, put those motors in series instead and you have 20 ohms. That's only 1A and 20W.

[Patrick]

Originally Posted by BrianG

Well, it's because you are changing the motors from parallel to series. The resistance is changing by a factor of 4.
So, just to make up some easy numbers, let's say each motor has 10 ohms. In parallel, that's 5 ohms. With 20v (again, some easy arbitrary number), that's 4A for 80W.
Now, put those motors in series instead and you have 20 ohms. That's only 1A and 20W.

Oh yeah, I know what you mean now. I forgot about there being less resistance of two parralel motors compared to one.

[BrianG]

Personally, I would solder the wires together instead of making a jumper connection. Even do it on the EVX board to really clean things up. Although, a jumper is reversable, so it depends on if you ever want to go back to stock wiring...

[jimbob]

with deans a jumper is really easy and i think its best just to keep it like it as... as you can go back so easily :027:

unless your going to run 540 19t or 17t motors i think you will be going back to 12 cell pretty soon