Experimenting with 32v DC fuses at 48v and 68v

[Ianhill]

Agu fuse holders I've been using at 60v 16s lipo with a 60amp fuse running 57amp and it holds with no nonsense tripping, I've not accurately blown one I just placed it with the neutral on and flashed the live to it and dead shorted 2 of them with my pack so i could physically disconnect and stop a Lipo fire if an arc did occur and it just blew the pants off them with no issue, I also used the maxi blades at 48v 40amp with no probs and done same with them.

I always tend to design my system so the fuse is the weak spot running around 90% capacity and the wire around 60-70% loaded to keep heat in the conductors to a minimum and allow breathing room in a fault to have low resistivity and deliver a strong short circuit current and activate the fuse fast, most fuses are rated around 110% of their design current and the stronger the surge the quicker the disconnect but the fuse itself needs to be able to extinguish the arc with normally a distant the voltage can not jump and then sand as an added measure in case the system goes outside it's voltage design limits which is highly unlikely with a battery system so you see mostly open air fuses on systems under 48v or classes as a non danger to life but will still hurt if you shove them on your tongue so if the agu fuse did blow don't go putting your thumb inbetween the contacts depending on your resistivity and voltage potential with the item current may flow and a dc shock can hold you on and burn you bad so only play if you have signed a waver with yourself no complacency.

 

[Mr. Bungle]

That was a very informative and helpful answer! Thank you! I'll be searching for higher voltage rated fuses now. Hopefully it'll plug right in and everything will be safe.

 

[liveforphysics]

Someone told you wrong, because molten glass actually conducts electricity great rather than being an insulator like cold glass.

The sand is to absorb energy in the phase change of melting the sand, and it's cheap and works well with the arc pulse quenching of AC currents. My favorite for DC after testing many materials is Nomex paper strips laid alongside the fuse element. Faster and higher power arc quenching than sand or glass or mica etc.

If you guys were running a low enough impedance battery, you can get that 32Vdc automotive fuse package to consume itself in plasma. The Maxifuse size is just as cheap and has a good deal more plasma gap and more friendly towards Ebike current level wiring terminations.

When I was taught how a sand fuse works I was told it quenches the arc by turn a small amount of sand into glass with the heat of the arc helping insulating itself and extinguish the arc thats why a fuse with no sand will melt a large area of conductor compared to the one with sand. The one with out sand relys on the conductivity of air so the higher the voltage you go the larger the spark gap and more of a need for sand.

 

[Ianhill]

Someone told you wrong, because molten glass actually conducts electricity great rather than being an insulator like cold glass.

The sand is to absorb energy in the phase change of melting the sand, and it's cheap and works well with the arc pulse quenching of AC currents. My favorite for DC after testing many materials is Nomex paper strips laid alongside the fuse element. Faster and higher power arc quenching than sand or glass or mica etc.

If you guys were running a low enough impedance battery, you can get that 32Vdc automotive fuse package to consume itself in plasma. The Maxifuse size is just as cheap and has a good deal more plasma gap and more friendly towards Ebike current level wiring terminations.

When I was taught how a sand fuse works I was told it quenches the arc by turn a small amount of sand into glass with the heat of the arc helping insulating itself and extinguish the arc thats why a fuse with no sand will melt a large area of conductor compared to the one with sand. The one with out sand relys on the conductivity of air so the higher the voltage you go the larger the spark gap and more of a need for sand.

During that phase change what happens when the sand absorbs energy from the arc ? It becomes molten glass and then that has too cool to become an insulator with the arc present and conducting through while it's at the molten stage and then extinguish when cold/solid ? I'm be no means an expert I only done 3 years basic college so I can lay wires and not lick live conductors and kill myself so I'm not exactly tesla himself so I'm gonna have a dig about on this one see the sand in slow motion visibly watch the arc see what's going on.

I didn't realize molten glass conducts, to me that sounds idiotic to even put it in the fuse if thats the case how does it cool after the phase change during the arc if it's part of the current path and in the arc ? Lots of questions time to get some deep answers.

Now much energy does glass need to stay molten and can the arc provide it clearly not as they been used in industry for many a year so I'd like to have a fresh look at this.

 

[amberwolf]

Someone told you wrong, because molten glass actually conducts electricity great rather than being an insulator like cold glass.

Does that also apply to silicon wafers? If so, that could explain why FETs during failure explode into plasma so well.

 

[Ianhill]

Doing a quick search I found that HRC fuses use compressed silicon dioxide powder with a melting temperature of 1610°c and boils at 2230°c, an electrical arc can have a temperature of up to 19,400°c and that is enough to consume the remaining conducting metal inside the fuse to a liquid and a gas aswell as the silicon sand.

So a high rupture current is past then the plasma arc is created at the spark gap where failure has occured and starts to consumes the conductor from a metal to a liquid then a gas, while the silicon is also being liquified and then vaporized taking energy out the plasma arc to phase change both materials from a solid to a liquid and then a gas.

It makes sense at this point the mixture of silicon dioxide vapour and the conductors vapour will conduct electricity but what is the resistance of this mix I do not know, so it leads me to think that the arc spreads out and breaks down over distance and then everything cools to leave a mess and broke the equipment infront with the induced high voltage that comes with the plasma arc.

Other than being interested I don't have the qualifications to get straight to the answer this is material science I'm just a basic spark so more digging is required but I bet it's got something to do with the arc gap as the bigger the rupture current the larger the length of the fuse from basic observation.

One thing I've reminded myself is the dangers of an arc flash within an industrial setting with the danger to kill from the flash alone up to 20 feet when some serious shit goes wrong.

 

[Ianhill]

This missus got a galaxy note 9 they do 960fps so I may setup a fuse blowing table when I got time with good light exposure and then a few in the dark and pop some open air fuses and view the arc. Then I could take a few sand fuses and drop them across the 48v 400amp supply in slow mo and see how they fair then repeat as I lower the voltage down to 12v, I'll have to test if 960fps is fast enough to capture it in detail but I can watch the frame front of a lighter so it should be quick enough to capture the arc.

 

[DrkAngel]

Just to note:
Using a 32V fuse effectively and safely with "48V" battery.
14s 51.8V Lithium battery @ "full" 58.8V.
Place 32V fuse between 2 x 7s segments!
Voltage across fuse will not exceed 29.4V.
(Will not affect BMS function)

20s (84V)
Fuse between 3 (7s 7s 6s) segments ...
etc.

 

[Ianhill]

Just to note:
Using a 32V fuse effectively and safely with "48V" battery.
14s 51.8V Lithium battery @ "full" 58.8V.
Place 32V fuse between 2 x 7s segments!
Voltage across fuse will not exceed 29.4V.
(Will not affect BMS function)

20s (84V)
Fuse between 3 (7s 7s 6s) segments ...
etc.

Good old lead acid came like this and its handy for Lipo too but a nickel strip 18650 not so much.

Top work on the scooter front I'm a lover myself wish I was in the US so I could get my hands in an ezip 400 fork they are perfect upgrade for a razor e300 I'm sure I could squeeze a 6.5 rim in there with the lower profile tyres and make a sick front end.

 

[DrkAngel]

I build 7s 25.9V batteries for a multitude of 24V eZips. So 2 - 7s segments is great for me, (14s for my 48V 750\1000w switchable, 14s lets me hit 30mph!), saddle bag deployment or otherwise ...

 

[Ianhill]

I build 7s 25.9V batteries for a multitude of 24V eZips. So 2 - 7s segments is great for me, (14s for my 48V 750\1000w switchable, 14s lets me hit 30mph!), saddle bag deployment or otherwise ...

12s got me 36mph with the 1600w 48v boma motors, on 16s I got 48mph and kept it there for nearly 20 mins I'd covered 15 miles lol, that was around 2 years ago long before these dualtron scooters, it's time someone put them back in they box claiming to be the fastest electric scooter in the world and the first dual motor

I can't put my finger on the thread but I've seen 3 motors all chained on one wheel all 1kw brushed running 7kw and that done 70mph.

 

[Brendon_m]

Bit of an old thread but I recently experienced a cross wire between a 12Vdc circuit and a 141vdc circuit and thought you all might like a picture. Turns out a 32Vdc rated automotive blade fuse will break the circuit but not happily and I probably wouldn't rely on it...

Top is after a normal 12Vdc short, bottom had a 141Vdc short across it.
It made a buzzing sound for a few seconds before it finally let go. Scary times.

 

[amberwolf]

Top is after a normal 12Vdc short, bottom had a 141Vdc short across it.
It made a buzzing sound for a few seconds before it finally let go. Scary times.

Yes...worse if it keeps arcing and heats enough to set fire to the plastic.


BTW, I'd recommend checking the rest of the circuit (both systems) to be sure none of the interconnects anywhere were damaged in the process. (they may still "work" fine, too, but have heat or arc damage and be higher resistance). I've had that kind of problem after a miswire once, and it eventually caused other problems.

 

[Phillip Johnson]

so i wanted to see if a 32v dc rated fuse is going to work on a 48v ebike battery pack. specifically if the arc would quench, and how quickly. apparently it works just fine. simulated dead short. popped instantly. arc didn't linger.

i also prepared a modded fuse filled with sand taken from a larger fuse

as expected it worked as well.

Thanks for posting this info. I have a video using a 32V 30A fuse temporarily in a 56V EGO battery and even though I said it should only be temporary and I know for a fact it will interrupt the current and blow just fine I was cautious about saying in the video to simply use it as a trace fuse replacement. I had a viewer get a little to into explaining how and why it could be a really bad idea and tried to explain the catastrophic failure which showed complete ignorance. I am glad to easily find more info than I have tested for myself. Viewer even tried to say that it was a fact that the fuse would not blow at 30A with 56V on it. The only issue of course is if the fuse can extinguish the arc effectively at higher voltage. A larger fuse is needed for that which of course is not physically able to fit is why EGO simply uses the trace fuse. Thanks!