Fuse Size

[truly_bent]

I woulda thought all that placement-of-the-fuses-stuff would be obvious perfesser.

I think that the only thing a fuse on the input side of the controller might not protect would be a voltage spike feeding back from the motor. If sufficiently high, it could damage the FET's. This would likely happen in the event of a winding short, since there would be collapsing fields.

But, MOV's (Metal Oxide Varistors) would be better protection for voltage spikes than any fuse is likely to be. They take up less space too. 
 
Jeff

[Morgen 3Eman]

Hi Jeff,

Apparently things are more or less obvious depending on how thoroughly one looks at things. 

A single component failed on my second MP3 controller. I think it may be the linear voltage regulator, or rather, may have been.  The 30 amp fuse on the input to the controller blew.   The FETs were all fine.  The only damage to the circuit board traces were from the hole burnt in the board by the failed component. 

Another, later, posting showed a photo of the exact same component failure as mine.

By the way, do you have any fuses at all in your installation?

Fuses on both leads of the controller input power are not needed.  One will suffice.

TTFN,
Dennis

[RobbyRob]

Awesome we killed this topic I think Ha ha. I am learning so much thank you all.

[truly_bent]

Okay, I stand corrected. The lead feeding the on board voltage regulator can apparently handle more than 30 amps long enough to pull down a 30A fuse.

There, I said it. I am now officially ashamed.

And yes, I have a single heavy-duty automotive 60A coming off the the battery lead. And before you ask Dennis, it is on the positive (red) lead. I selected 60A for the 3C max current.

It's automotive, so it probably has a few second time-delay. I'm not so worried about toasting any cells in that time (maybe I should be), although I'm considering one of those 50A 48V marine circuit breakers. Probably quicker.

[Morgen 3Eman]

Sorry, Jeff.

I had no intention of causing you embarrassment or hurt feelings.  I just disagreed with what you were saying, based solely on my personal experience.

I expect you to do the same when your data disagrees with something I present.

Again, I'm sorry  your feelings are hurt.

TTFN,
Dennis


   

[truly_bent]

The whole discussion has been a good one for me. It's forced me to take a more careful look at what I'm doing to protect the system.

And I need to learn to swallow my pride with less fanfare.

Jeff