I was thinking about this the other day, can this really save your ESC? If for some reason the ESC pulls enough current to blow the fuse, I’d imagine the ESC is already dead… Like if you blow a mosfet or something on the PCB shorts its already too late, the fuse really only protects the battery. This is where an easily accessible loopkey is important. Anyways when something like this happens, we usually see that the ESC usually just fuses itself. Also I thought a sudden battery disconnect at high current has killed ESCs/DRVs.
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I’m thinking the same. I’m no electrician or something, but I remember in fpv drone hobby we have something called “smoke stopper”. Smoke stopper is used to test out the drone electronics and limit the current, so if something is soldered wrong, it won’t damage it. The most obvious way to do this was to power the drone with fuse in series. However people found out that the fuse was just too slow to protect the electronic. I imagine here in esk8ing the situation is same, fuse is just too slow to protect sensitive electronic. I use fuse to protect my battery from turning into fireball, not to protect my VESC.
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We have like 2 connectors to solder correctly, if you dont count the reciever/bluetooth module
So pretty hard to do it wrong imo
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Yeah, in esk8 the fuse is not for testing, it’s there permanently. And as I have said, for testing the fuse is not good protection anyway.
But what if there is a short in phase wires, motor coils or somewhere inernaly. Soldering on VESC might break due to vibrations. Mosfets might fail. I mean I’m not electrician, maybe these things are not really problem. VESC is complicated and I don’t understand it. Of course I try to build my boards in a way that these things are less likely to happen. But I don’t know, so better safe than sorry.
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Obviously depends on the fuse used (fast vs slow and rating) but no, I’m not saying it will guaranteed save your esc… Hence why I said can and not will 
Do you mean when an esc blows, you see it close circuit with the battery? I feel like it normally just dies open circuit from the amount of failures I’ve seen but definitely see the point about protecting the battery in that case. Empirically, when my unity blew, it left the circuit open without killing the battery.
You would be suprised to see how long my units pcb and heatsink was acting as a 2kw heater lol
It went on for minutes untill i menaged to disconnect it 
The problem was my battery was to weak to fuse it out quickly and safely, on my new build that wont be a problem haha
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This is basically what I was trying to say.
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Then wouldn’t the battery be open circuit and not be damaged?
If an esc fried closed circuit somehow, I could see a fuse saving a battery. Or if something went haywire and it just allowed full battery to motor output, that would be bad if you didn’t have a loopkey.
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I feel like this has been addressed multiple times, but since it is related I would love to get some feedback here. For those of you who fuse for charge only do you put the fuse on the positive or negative side?
Charge Only Fusing - Positive vs Negative Side
- I fuse the positive side
- I fuse the negative side
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I don’t think it really matters since we aren’t tying the power supply to a common ground like a car chassis.
If we used negative terminal as common ground like cars do, then you’d want the fuse as close to the battery positive as possible.
@Pimousse you are an awfully smart fellow, any opinion?
There’s no chassis but there is definitely a “common” connection in a board, the negative, and all of the non-isolated devices are referenced to this point. If this was not done then each device would have no way of knowing what the signal or power they are receiving are referenced to, they would have no idea what the voltage was for any signal or power they received.
It’s often via a long, convoluted path (causing all sorts of signal and power integrity issues) but all of the Negative or Ground connections in a board are electrically connected unless an isolated power supply or comms chip is used.
If the negative side is fused, and the fuse is blown, then this reference point/voltage is lost. Some devices might not care but others, that might still be receiving signals or power from another source, can misbehave quite badly if the ground is disconnected (“lifted”).
I recommend fusing the positive, just in case something might be sensitive to losing its ground connection.
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The fuse holders have a red wire on them for a reason!
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Thanks for the explanation!
If you have the free time to keep on schooling me, why do cars 12v systems use an earth ground?
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I’m certainly not any kind of expert on automotive electrical stuff but I don’t believe there is an earth ground for any vehicle. All grounding is done within the vehicle and not to a true earth ground since the current is created within the vehicle and so only needs to return to that same source.
There is a “common”, often using the chassis on older vehicles, but that is just where all the negative connections are made so individual wires aren’t needed (to save money).
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I second @Battery_Mooch
In the good old times when we made single motor builds without any electronics other than the ESC, fusing the positive or negative side didn’t really matter.
But nowadays, we have a lot more devices and cutting the ground path isn’t a good idea.
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After doing some dumb things, I now fuse the balance wires.
And the main discharge [positive] with a fuse soldered into the xt90s loop key, but its NOT to protect the esc’s, its to prevent thermal runaway of the main pack if a dead short happens from being dumb or bad crash. So its rated to about double my expected peak battery load, and the hope is it would still blow in a dead short. Its not without the downside of potentially loosing breaks while ridding, but with appropriately sized fuse I hope that would be low chance of happening.
For people with really high power systems, the size of the fuse would probably not be very practical.
I still wouldn’t recommend to anyone, you would need a good level of electronics experience and willingness to accept the possible increased risk.
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isn’t the ESC supposed to be receiving enough current from the rolling motors even though the battery is disconnected ?
Tried disconnecting battery and I had no brakes while rolling down hill. Ymmv but that was exactly what I expected.
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