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Saw this thread pick up again, don’t want to derail too bad but why would you want to fuse the antispark? Seems like a system fuse would be more reliable and effective with commercial options available though I still dont see a good reason to fuse the battery output for all the same reasons my bms is bypassed which is a whole can of worms too big for this post
Sizing a dc fuse for the battery amps that would protect the vesc but not cause nuisance tripping is going to need to be calculated correctly or it wont protect the vesc.
Dc voltage ratings are super important imho to getting the fuse to actually clear the fault in a way that is predictable, non destructive to the ocp components, and can protect the downstream components. Playing with the variables and finding a solution through trial and error is a recipe for false security and disaster. Using automotive fuse wire is a bad idea imho when proper commercial fuses from trusted manufacturers is available but maybe I just don’t know the product well enough to judge.
A fuse is in principle an introduced point of resistance in the circuit so that the heat of a fault will break the link at that point. Having that heat at the loop key sounds like a bad move. Under normal fuses get warm and having one encased in a loop key is going to be a huge variable to consider.
I guess I just can’t see the advantages of this approach, if you pop a fuse the enclosure is getting opened. Having it more accessible by being a part of an external part could be done by just adding an external fuse holder.
Having the fuse on a charger port i can get behind. No need to risk having unprotected voltage available outside the enclosure. Loop keys are also a risk in this way but mitigated by being in series with the esc and other components reducing the available current.
I don’t get it sorry
My old vehicle came with some 10 AWG fusible link on 6 gauge(sae) cable between alternator and battery.
The service manuals say when a fusible link blows the wire inside is supposed to break and the wire insulation stretch out.
When my link blew, this did not happen. it looked fine, and later when cut off and replaced, it tested fine continuity wise, but it would pass no charging current.
THe manuals say to not use a regular fuse in place of fusible link, though many do apparently without issue, and i guess modern vehicles have phased out fusibke link wire entirely.
I Agree it is likely a bad idea for a loop key, but perhaps better tha 18awg of silicone wire.
I think they are a slow blow design. I fondled some in a Napa autoparts store once long ago and it was way overpriced, and did not impress me enough to buy any. I eventually went with a 150 amp bussman circuit breaker on the 4 awg.
The no name brand would trip after few minutes of 100 amps. Thankfully i had it wired so voltage regulator would disconnect at same time, thus saving the diodes in my externally regulated alternator.
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Space saving is my reason
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I won’t own a board without a discharge fuse, and personally see it as irresponsible to not consider circuit protection should the ESC develop a dead short. I’m an electrician, and I don’t do circuits without fault protection.
I’ve had a stormcore catch fire overnight at home. The fuse didn’t operate in this case, but a correctly chosen fuse is extremely unlikely to fail in use. The consequences for not disconnecting a shorted ESC from the battery may cost your house, pets, or lives. What if the board is being built for someone else, do they know the risk they’ve taken on?
Of course, over discharge of one or more cells in a pack could still lead to fire. I like lights supplied by the BMS discharge. If the lights going - the cell groups are still within voltage limits whilst riding.
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This seems a great way to utilize the discharge function of the bms and can still bypass it going to esc
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Would a short be that dangerous? I mean it might save a really weak battery. I mixed up +/- once and the XT90 got vaporised and blackened my hands or a bullet connector or something would get that soot buildup oxidisation crap or the wire would jump back slightly. Idk how I would short a moderately large pack.
Not sure I understand exactly what you’re asking but ill shoot and tell me where im off. A short is bad because it’s uncontrolled. Its pretty much a race to find the weakest link in the system and murders it. If the xt90 partly connected is the weakest point it will destroy that. If one of the nickel strips or parallel jumpers is the weak spot - nuke that. If it’s a cell that just cant take it anymore - ded. All in all you’re gonna have a bad day
The fuse is an intentional weak link. Sized well and in the conditions it is intended it will blow before anything else is damaged AND not when everything is fine. That is the hard part. If it isn’t sized right or is being used in the correct conditions it could still cause damage or wear to the system in some way. Like when your circuit breaker trips so you tape it closed - or replace a 15a breaker with a 20a so it doesn’t trip as much… you’re gonna have a bad day
In short (HA!) it is bad. Electricity only does what we want it to do when the total system is known and accounted for. Planning for a short lets us choose where a system will fail because otherwise it is a forensic examination to find out what went wrong
And the technical term for that soot and mess you got from having a reverse polarity is called the magic smoke. Wanna keep that on the inside 
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With the bms putting out the full battery voltage what did u do for lights? Tons in series, or big resistor, or…?
dw I’m not sure I’m making sense, I know a fuse could save us from breaking something else but a short on an esk8 on the discharge leads even in the worst case scenario the short stopped itself instantly. It might turn your broken VESC into a slightly more dead VESC but it’s unlikely to save from a fire imo and definitely wouldn’t do what a smoke stopper does.
My VESC was fine the soot I was talking about was just on the plugs. Here is an extreme example from Styropyro on YouTube it’s the only example of the stuff I can think of. That’s a nut and bolt across 60v of car batteries but that messy black stuff is holding it off. That assembly was copper coloured.
A small fuse is a little bit of a risk while riding and a big one will allow lots of current especially for short amounts of time or plenty to start a fire.
I disagree with @TimR about fusing the discharge leads making that big of a difference. You seem adamant about having a fuse for safety and use the word irresponsible but you leave the VESC plugged in and you did have a fire with a fuse installed and it didn’t work. I’m also not sure how to tell what burned first in a melted esk8. If it was caused by a spontaneous VESC short which to me seems unlikely it could still get plenty current to burn within the amount of current we normally use. The vast majority of fires would not be stopped with a fuse on the discharge leads and those caused by electronics fault while unattended would be stopped by disconnecting it with a loopkey for example. Sorry writing this is long and a bit of a mess.
In summary a fuse would only help a short on the VESC leads which is not most of the fires. You would need a big fuse so lots of current (often enough for a fire) would still flow, of those extreme ones most would instantly fail somewhere else like a connector and of those shorts all the ones which were unattended could be actually stopped by a loop key and while riding a fuse is only going to cause you to lose brakes or power especially at speed.
We are talking about the same soot, let too much out of your connector and it will stop working.
I agree that one fuse on the discharge to the vesc won’t do more than protect the battery from a short, it should probably be sized so that it would only blow from a direct short - maybe somewhere north of the abs max current setting so depending on the vesc something like 200a fast blow or something (do not use my example). What this would do is clear a short after the fuse and protect the battery.
It would do nothing for the vesc or anything else nor would it prevent a fire caused by an overcurrent. Thats not its purpose and it’s not really possible imho to get it to do more than that. If there was a vesc fire you lose breaks so i dont see a disadvantage here compared to not. It would just eliminate one part of the risks here. Edit: the risk being a vesc fire that shorts the battery terminals
A fuse on the charge port just protects the charge port, wire, and bms from a short or over current. I had a 15a fuse blow on my charger port once because the calibration for my charger was way off - more than 5a. I had to bench the charger and recalibrate it - if I didn’t have a fuse it would have overheated my charge connector and could have started a fire. That’s exactly what it is intended for and after it blew i was able to ride the charge i had left home and figure it out. That fuse also protects from getting water or debris in the charging port and keeps it from being able to have full battery amperage there - my pack will dump 1000+ amps in a theoretical short though I’ve never tested it
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I use little DC buck converters. Either 24V or 12V. A lot of the Ali express lights are garbage too though I’ve found, while a few so far are good.
Some headlamps I’ve had to replace the drivers by various means and with headlights I typically rechip them to warm white.
I’ve just bought some little coloured lights with an M10 threaded shaft that are cheap and work okay on 12V. I’ve run two of those in series of a 24V buck regulator.
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