nicobie
100 MW
Some people use the breaker as a system on/off switch. I've never done this.
Circuit breaker blew like a fuse
- Thread starter Zambam
- Start date
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.
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..
It’s a large subject. I think you’ll find that amberwolf, amongst others, has written plenty on it.
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
1 mW
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.
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
1 mW
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.
Turns out the MCB in the video looks like the one in my moped! I finally took my failed (open circuit) MCB apart yesterday.
What's the function of the red thingy? It has 9 metal plates mounted on insulators, not connected electrically to each other or to anything else.
Answering my own question, which was also asked in a comment in the video, reply says it's an arc arrester. That makes sense!
Looks like it didn't work. Those contacts look pretty burnt.
That half of the 2 pole interlocking breaker failed open a long time ago, so I switched to the other pole. which recently started tripping while riding (happened a few times). That's dangerous so I replaced it with this one https://www.amazon.com/dp/B0C944KS8V?ref
eee291
100 kW
The lack of pre charge can also kill these circuit breakers.
Lack of pre charge causes charred contacts, charred contacts cause heat, heat causes it to trip, flipping it on to continue riding causes more charring.
Lack of pre charge causes charred contacts, charred contacts cause heat, heat causes it to trip, flipping it on to continue riding causes more charring.
marty
10 MW
If I am understanding correctly? When one breaker is turned on, other one goes off. So that only one battery can be used at one time. How does that happen? What makes other breaker turn off?
Not only contacts were charred, plastic by the solenoid trigger (coiled magnet wire) also melted from the heat.
The moped has a key and blue tooth remote to power up the moped. Breaker was used only when I worked on the moped or disconnect the battery, cycled probably less than 100 times.
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It was not flipped that many times since it was not used to power up the moped (breaker under locked seat). Moped has a key and blue tooth remote to power moped up. Breaker flipped only when I needed to work or the electrical system. This suggest the breaker had high resistance from the factory which caused it to run hot constantly. You can see the melted plastic near the solenoid trigger.
That's correct! There's a trigger between the 2 breakers (riveted together- drilled out). You can see the black trigger on the left breaker.
This moped can be fitted with dual batteries (different in size and shape, 1 under floor, 1 under seat). Only one battery can be selected at a time (cannot be put in parallel with the breakers).
marty
10 MW
Will your new 2 Pole breaker work that way? Don't think it will.
New breaker will not work that way, nor do I need it to. I have just one battery under the floor. With the warmer weather, getting 60 miles + per charge (LFP 73V 30 Ah). Space under seat is for storage.
So, no never any current flowing when you switched off, but would've arced every time you powered the system back on due to controller caps? No precharge resistor? Decent sized controller with big caps? If so, that's a hard life for a switch and you might've been lucky to get 100 such uses out of it.
The contacts are high resistance only due to the charring, as eee291 explained. You have both a new and old MCB on hand, so can measure the resistance. It's a vicious circle, with the higher the resistance, the higher the heat, the higher the resistance.
You wouldn't have seen melting without charring, and charring without arcing, so best to address the arcs.
Less better would be to keep a tab on the number of switch activations and replace the MCB every ten or twenty times, but certainly not as many as 100.
Or better than less better, measure the switch resistance after each time you use it, with a predefined acceptable/unacceptanle Ohm figure in mind to determine when to replace the switch.
The contacts are high resistance only due to the charring, as eee291 explained. You have both a new and old MCB on hand, so can measure the resistance. It's a vicious circle, with the higher the resistance, the higher the heat, the higher the resistance.
You wouldn't have seen melting without charring, and charring without arcing, so best to address the arcs.
Less better would be to keep a tab on the number of switch activations and replace the MCB every ten or twenty times, but certainly not as many as 100.
Or better than less better, measure the switch resistance after each time you use it, with a predefined acceptable/unacceptanle Ohm figure in mind to determine when to replace the switch.
The controller has 4x 330UF 100V electrolytics. Have you seen this post from E-HP On/Off switch autopsy where he used a 40A AC circuit breaker as a switch thousands of times with no pitting or burnt contacts? Why did mine burn and his didn't? I am sure his controller also has big capacitors.
Contact material, contact bounce, activation force and speed, all come into it.
Quite possibly his breaker was better for the task. I'd bet on less contact bounce.
He might've had an old high resistance battery, high resistance wiring, don't know.
But there's also a direct relationship between arcs and voltage. You're using 73V. He was using?
Doesn't much matter the reason, because any old MCB will be up to the task ... if you implement a precharge system.
Could be as simple as a wire protruding from each side of the MCB that you touch together, hotwire style I.e. parallel bypass loop. Get to enjoy watching the sparks that way, instead of having them destroy your contacts.
Quite possibly his breaker was better for the task. I'd bet on less contact bounce.
He might've had an old high resistance battery, high resistance wiring, don't know.
But there's also a direct relationship between arcs and voltage. You're using 73V. He was using?
Doesn't much matter the reason, because any old MCB will be up to the task ... if you implement a precharge system.
Could be as simple as a wire protruding from each side of the MCB that you touch together, hotwire style I.e. parallel bypass loop. Get to enjoy watching the sparks that way, instead of having them destroy your contacts.
