# I blew up my controller and now I'm trying to understand them better.



## Qer (May 7, 2008)

Nope, getting a 40 Amp controller won't automatically mean it won't blow, getting a high quality controller will, however.

A motor that's stalling is more or less short circuited, the rating on the motor isn't the max current it can draw, it's the max current it can handle during a certain time period. A motor can, however, be temporarely overloaded so even if the motor is rated 36 Amp it can temporarily handle current much higher than that. Same thing with the wires, even though 10 gauge wire can handle 14.8 Amp that's continuous current. If you overload it it will eventually burn off (like a fuse), but it will take a while.

My guess why the controller blew is that it simply failed to protect itself. Since a stalled motor can draw insane amount of current the controller must always limit the current to levels it can handle. When you changed the gauge you had less voltage drop over the cables and if the controller were already on the edge of breakdown this little difference might've tipped it over.

So, no your controller shouldn't have blown. I'd contact the manufacturer and ask for a warrant replacement.


----------



## dskippy (Feb 11, 2010)

Qer said:


> Nope, getting a 40 Amp controller won't automatically mean it won't blow, getting a high quality controller will, however.


Well then how does one use a low-quality motor controller without blowing it up? I had a 25A controller, and simply plugging it into 10 gauge wire on a 24V source killed it. It makes sense that I should use the wire that is coming out of the controller. It looked like 12 gauge to me.

Also using a 25A controller with 12 gauge wire, I was only getting 15A of current. Sounds to me like actually getting the full 25A would have killed it. That seems strange doesn't it?



Qer said:


> My guess why the controller blew is that it simply failed to protect itself. Since a stalled motor can draw insane amount of current the controller must always limit the current to levels it can handle. When you changed the gauge you had less voltage drop over the cables and if the controller were already on the edge of breakdown this little difference might've tipped it over.
> 
> So, no your controller shouldn't have blown. I'd contact the manufacturer and ask for a warrant replacement.


I think your making a few assumptions here that are wrong. My motor wasn't stalled. In fact it wasn't even plugged it when it really blew. I had everything but the battery plugged in, when to plug them in, and then got a huge spark, which burned the connector a little bit. This made me worry about the motor so unplugged it. The I tried to reconnect it and got a another big spark. The sparks are common, though not generally this big. Whenever you close a circuit without a switch it'll happen. So I figure I just needed a switch. So I got a beefy switch that could handle it and then, without the motor plugged in still, the controller blew when I switched it on.

I feel like I need to have smaller wire for that controller. Are you sure this isn't my fault that it blew up? Sounds like my fault. I just wish I understood the ratings before I go another one. Also I wish I knew the way to protect it and ensure I don't blow up the next one.

-mike


----------



## Qer (May 7, 2008)

dskippy said:


> I had everything but the battery plugged in, when to plug them in, and then got a huge spark, which burned the connector a little bit. This made me worry about the motor so unplugged it. The I tried to reconnect it and got a another big spark. The sparks are common, though not generally this big. Whenever you close a circuit without a switch it'll happen. So I figure I just needed a switch. So I got a beefy switch that could handle it and then, without the motor plugged in still, the controller blew when I switched it on.


Um. Ok. Either it was already shorted or you killed it by the current inrush. Precharge resistor might be a good idea.


----------

