fuses!!!

[thelarkbox]

 

[guerney]

Those fuses don't always blow so quick in general, according to a dude from Grin Technologies, in a video of a presentation about battery fires @saneagle posted a couple of weeks ago. Sometimes they effectively become resistors spewing heat, instead of blowing. I may daisy chain two or three together, to increase the probability of getting one quick blow.

 

[Pingk]

In my opinion fuses are cheap enough that it's not worth the risk to skimp a few extra pennies for a potentially faulty part.

Spending an extra 20p on a fuse from a reputable supplier is gonna be cheaper in the long run than accidentally blowing your controller.

 

[AGS]

How is a fuse going to stop a controller from blowing up?

 

[Pingk]

How is a fuse going to stop a controller from blowing up?

If your controller can only take a maximum of 20A but you change a wrong setting and it tries to draw 30A, a 21A fuse between the battery and controller should blow first -breaking the circuit and hopefully protecting it.

 

[Tony1951]

If your controller can only take a maximum of 20A but you change a wrong setting and it tries to draw 30A, a 21A fuse between the battery and controller should blow first -breaking the circuit and hopefully protecting it.

This is an interesting problem. One of the key issues about fuses and electronics is that a lot of electronic devices will blow rather quicker than the fuses in fault conditions, so they may be destroyed before the fuse interrupts the supply. I have no idea whether power controllers fit into that category.

 

[Cisco-man]

This is an interesting problem. One of the key issues about fuses and electronics is that a lot of electronic devices will blow rather quicker than the fuses in fault conditions, so they may be destroyed before the fuse interrupts the supply. I have no idea whether power controllers fit into that category.

I always felt that a fuse was primarily there to protect the power supply and supply infrastructure, not necessarily the device you were attaching!

 

[Tony1951]

Well they are almost always included inside electronic devices too, so they are probably there to protect the device too in such a case.

 

[Cisco-man]

Well they are almost always included inside electronic devices too, so they are probably there to protect the device too in such a case.

Agreed, for internal circuit fuses. If you buy any device that’s got a 13A plug on it nowadays though you’ll likely find a 13A fuse in the plug, even when the device itself draws small amps. I’ve never been happy with that and I like to pop a 3A fuse in if I remember.

 

[AGS]

The fuse will protect the wiring. It won’t stop your controller from blowing. If you get a short circuit there is enough stored energy in the capacitors to blow the fets way before the fuse thinks about blowing.

 

[Sturmey]

In a normal ebike setup there are a number of overcurrent protections that I can think of..
The battery BMS FETs should trip a little over the batteries nominal max current rating.
The battery normally has a back up fuse of higher rating over that again.
The controller normally has a shunt that measures the battery current and should (hopefully) limit/shut down/error in event of motor short.
Low wattage carbon resistors are used internally that will fuse if external shorts on 5 volt, headlight circuit etc
PCB tracks, are often intentionally very light copper with solder (low melting point) that will melt.
Battery balance wires etc are very small gauge and will melt.
External 5 v line normally via diode
Many components will 'blow' open circuit.
Good quality chargers normally have additional built in protections as well as the standard fuse.
A big problem I think can be when attempts are made to modify/repair by upgrading components . (e.g fuses or fitting thicker (e.g balance) wires in battery etc or replacing a carbon resistor with a ceramic resistor ( which can get red hot ) etc. I personally know of a house fire caused by the latter. The owner had a timer on his bathroom vent fan which he repaired by replacing the burnt out carbon resistor with a high wattage ceramic resistor. No one injured, just a new roof.