EV.6.6 Overcurrent Protection

Unless Specified otherwise. For example if the a fuse on the HV side of the TSAL blows voltage the voltage would drop to zero and the light would indicate no HV outside of the accumular when there actually is.

"a.) If the rating is lower than input voltage there is aa possibility of arcing through the air/vaccum. Maximo says even if a fuse is blown if the voltage is higher than rated there could be arcing. ""The fuse could effectively be overcome by thevoltage""

b.)  Rate your fuse do that is the weakest link in the circuit. Rate your fuse so that it heats up before the rest of the circuit. If a system runs at 10A if you pick 9A(it becomes a performance issue) if it is 11A it is a safety issue.

c.) Interrupt current is the current value at which it bypasses the fuse(most likely a welded contactor on the realy). So the point is to make sure that the interrupt current rating of the relay is higher than short current rating that way high current cant bypass relay. You want your fuse to be able to withstand the short circuit but not catastrophically fail because it. "

What can happen if the available short-circuit current is greater than the interrupting capacity rating of the "protecting" fuse?

If you have batteries in parllell and one of them has an internal short to where internal resistance pluments to zero then the other cells woulld be shorted to themselves creating and overcurrent senario you can prevent without fusing. 

Along with  proper fusing make sure your wiring can also haandle at leastthe  continuos current required. For example if a system is rcontionus running at 200A with a fuse rated for 200A don't have a 22Gauge wire connecting two. Because typically 22 gauge wire is only rated for about 6.3 A. Every thing from fuses, relays, wires, busbars, etc need to rated correctly.

"Fuse wire/ cheap fuses usually have no voltage ratings because the rating depends on the length used. And for the cheap ones the manufacture provides a poor/no datasheet. And for Low voltage(LV <= 60V) fuses have less confidence than high voltage protection fuses?????

1.) The reason this rule exist is so that main accumaltor fuse blows before any of the individual cell fuses

2.) if a cell draws over current the fusible link will blow the increased load on the other 3 parrallel cells will cause a voltage drop. That can be registered by the BMS. This rule was was alot easier to justify to the judges since there were only 4 in parrell as opposed to something like 20.  

3.) data sheet or validation in ESF"

"UNCC Alex Volmer: I think this is referring to all conductors in the high current path I.e crimping a 10 amp rated wire to a 7 amp rated pin best design would be to fuse to the lowest current rating but say you’re looking at your DC-DC converter connector and your main accumulator fuse is 180 but your DC-DC converter connector is only rated for 160 you either have to lower the pack fuse to 160 or have a separate 160 amp fuse within 150mm the DC-DC converter connection

Trysten: Basically if you use a 20 amp breaker or fuse, and you step your wire  down to 15 amp rated wire you can’t do that and you have to add in extra current protection for your wire.

Berkely Nikhil: What they mean is when the wire gauge changes you have different ampacities. So for instance if the wire gets smaller then a fuse on the larger wire might not be adequate to protect the downstream smaller wire. 

Do you know of an instance where spec-ing a wires ampacity below the expected continuous current is ever advantageous? That sound just sounds like a mistake. 

Or as long we never do this I should have to worry about this rule affecting us?

Nope; your ampacity should always be comfortably above your expected continuous current. 

This is for instances such as charging where you have a smaller cable to charge than you might to connect to the motor/controller, but they're the same connector. 

You will definitely have to worry about the rule; it's for if you change wire gauge within a wire run. For example 12awg split to 4x 22awg then you need fuses on the 22awg wires even if you have one on the 12awg wire

Because one of the 22awg wires could pull all the current from the 12awg wire; which would exceed its rating but be ok for the 12awg rated fuse"

Some cells already have internal fusses that blow if over drawn iif so you don't need to have any upstream current except for the main Accumulator fuse found in EV.6.6.5