Circuit breaker blew like a fuse

[nicobie]

Some people use the breaker as a system on/off switch. I've never done this.

 

[glennb]

BTW, if you are reading this glennb, I do keep wondering about bypassing the CB while being very careful not to short the wires. Go easy on me if you reply. Thanks.

It’s a matter of what risks you’re willing to take with the BMS. There’s a reasonable chance a short circuit will destroy it.

If I bypass the CB, will the controller survive?

In the event of a short circuit, the BMS should react quickly enough to prevent anything else being damaged between battery and controller. Just remember that BMS aren’t designed with this in mind, that their overcurrent protection is not intended to have to deal with short circuits..

Do ebike controllers have their own built-in protection? Or is it generally not known if they have their own built-in protection from overcurrent? Has anyone tested this or verified it? Any subject matter posts about such tests?

It’s a large subject. I think you’ll find that amberwolf, amongst others, has written plenty on it.

 

[amberwolf]

AmberwoQUOTE: "Note that the controller to battery wiring being too small will not affect the breaker operation. Upgrading it to thicker wires will probably actually make the problem worse as current will be less limited by wiring resistance."


What is a breaker for then? I've read on diysolarforum.com (screen shots below) that CBs are to protect the wire only. No one argues on the solar forum about this. Does the ebike forum have a different opinion?

I'd like to know what the CB is for on an ebike? Is it to limit current, protect wires, protect devices or protect against a short? Which is the CBer's primary purpose - the one that's above all else?

It's a matter of semantics, and your particular point of view.

For best safety, it can be said that the breaker (or fuse) is to protect everything "upstream" (on the current source side of the breaker) of it against a short circuit "downstream" (on the load side of the breaker). So it is usualy placed immediately outside the battery terminal, so that any short circuit in the wiring, or controller, etc., in that battery-current-loop from battery + to battery -, will trip the breaker and protect the battery from that short circuit.

It also incidentally protects the wiring downstream from catching fire due to the current flow in the short circuit.


Some people choose to say it the other way around, that it's first purpose is to protect the wiring itself, and it only incidentally protects the battery. But the battery, if overloaded by a short, could start a much more dangerous and intense fire than a simple wiring fire, and be much harder or even impossible to put out, if any of it's own internal protections fails to disconnect it.


In a solar panel system, if the breaker is between panels and wiring, it's purpose is more likely to protect the wiring, becuase the panels probably wont' catch fire and explode from a short circuit like a battery can.

If the breaker is between battery and something else, then I'd stll say that it's primary purpose is to protect the battery itself, and incidentally it will also protect the wiring.




However, none of that has anything to do with the point I was making that you quoted.

If you have a certain breaker size, it will operate however it is designed to operate regardless of how thick or thin the wires to or from it are.

What you *should* be doing is sizing the *breaker* to handle the full load the system will ever continuously see, and then also size the wiring to handle that load as well.

If the breaker is tripping from overcurrent, and your present wiring is thin enough to present any noticeable resistance (gets warm or has voltage drop across it), then making that wiring thicker will decrease resistance and make the overcurrent even higher. That will make the tripping problem worse by however much more overcurrent there is.

 

[JackofHearts]

Interesting feedback. Thanks. I'm still not sure what I will do next.

Recently with the LA battery, when I give throttle from a stop on flat ground, power cuts out, the CB doesn't flip though, if I ease into the trottle it is okay, when speeding along, all good. My scooter is designed so if I pull the brake a bit, the trottle's power is cut, I haven't dug into it yet to attempt a fixing. It comes with lifetime service so I'll take it to the shop. It just started doing this today.

 

[JackofHearts]

Alrighty. I gave the ebike to a relative and then purchased a gas engine bike. All done. Problem solved. I will build a 48v solar generator so the LI batteries don't go to waste. Thanks again.