Been doing a lot of reading about using a fuse on the main discharge when bypassing the bms. Everyone seems to have a different opinion.
So is it better to use a fuse or not?
1 Like
I fuse the charge port but not the ESC.
7 Likes
I think general consensus here is to fuse charge port… Not so many are fusing discharge path including me.
3 Likes
Thanks, I will definitely fuse the charge port anyway. I’ll leave the discharge without then. I don’t want a fuse popping while I’m riding!
1 Like
A fuse will blow at a given current rating.
An esc may not blow if you give it too much current for a short bit of time.
For this reason, I’d rather not lose all connection to my esc by pulling too many amps. Can you imagine not having brakes while going towards an intersection? If that fuse blows, you have no more electric control of your board.
On the flip side, the blown fuse can save you from a blown esc. This is monetarily better for you as fuses are cheap but not worth the risk imo.
Tldr; I’m more afraid of losing control over my board than buying a new ESC.
13 Likes
Agreed, thanks
We might do a poll here. I personally run fuse on booth charge and discharge, I don’t want to risk short in ESC causing my board to go fire.
Where do you put fuse?
- On booth charge and discharge
- Only charge
- Only discharge
- No fuse
0 voters
1 Like
Great idea, be very interested
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.
7 Likes
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.
4 Likes
We have like 2 connectors to solder correctly, if you dont count the reciever/bluetooth module
So pretty hard to do it wrong imo
2 Likes
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.
2 Likes
3 Likes
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
2 Likes
This is basically what I was trying to say.
1 Like
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.
2 Likes
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
0 voters
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?