Fuse your charge ports: Ft. The smallest user serviceable fuse/holder

I also use the pico 3A to fuse the balance leads.

Do you have pics of your battery builds/wiring harnesses floating around?

Also, measuring continuity aside, is ther any visual indicator to tell if they’ve popped? Is the one convenient thing I like about other types

Pics, let me see if I can dig some up.

This shows (kinda) balance lead fuses. You can see where the balance leads have the thick heatshrink right where they attach to the groups. It’s marine double wall self adhesive shrink. I know the balance leads are not well organized in this pack :slight_smile: But they generally don’t cross over, and where they do there’s the same thick heatshrink.

I think there’s a charge port fuse under the tape somewhere… I’ll try to find a better photo.

There’s other weird things in that pack. There’s a break in the middle so I can charge the subpacks on a hobby charger (I made a JST breakout board. And I have a nice hobby charger). There’s a LittelFuse Midi inline on the discharge wire. AS150 for antispark, with a 3d printed housing to hold it in place. Some crazy looking AMASS 8mm and 6.5mm stubby high current bullets. 13s3p VTC5a (75a discharge).

No visual. If you have a pocket voltmeter ala @b264 that’s one way. But, fuses don’t generally pop! If one pops it’s usually because I did something stuuuupid. Otherwise I’m pretty worried, and ripping everything apart to check.

Also for the charge port fuse, I’m using M/F 4mm bananas, so if you do something stupid on the road, you can just bypass (or leave it disconnected if you don’t need to charge).

BTW thanks for making the thread. I think it’s a pretty good safety measure.

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Awesome. Will look more into them this afternoon. They look ideal.

And he’s back! LOL, miss you Sid, you leave us here in socal already im assuming…? Appreciate the cred, to not my credit though, @Arzamenable is actually the one who snagged them for me when were out at my pad in Lake Havasu riding around at some local pep boys / craigen / auto zone etc type place. But it has already saved me on my build and a buddies build since then. I got those things you posted above and it does make it way easier than having to resolder a new one, but not pad if you have to and one of my builds still just has it soldered with shrink.

Quick question cause Im too busy (lazy) to look it up and can’t remember…does it need to go on the positive side or neg charge wire? And should it go before or after the xt90 connector I use coming from the battery to plug into my charge ports? Pretty sure I did it however you told me but am blanking and another friend is asking… thanks and hope all is well brotha! @Bindings_McGee

Gone for the time being. If I’m recovered & have some money I’m going to try to come out for a week this summer.

Not the best, but check out this picture.

Green is “before BMS”
Blue is “after BMS”
White is the negative charge wire I tapped off of negative mains
Larger black wires are negative mains to ESC

As you can see, I fused before BMS (bypassed, charge only) but I’m actually pretty sure it’s better to fuse after BMS with the cheap shit we use. Closer to the battery is always ideal for fusing - moreso in the case of us imaging the BMS throws the reason for our fuse to pop. If we really wanted to protect our battery and BMS - fuse before and after.

I also know just about nobody here does it, but fusing your positive mains to ESC is also a really good idea. Closest to battery as possible. Most not-tedious and esk8 way I can think of would be to use midi style fuse w/hydraulic crimped ($30 for crimper on Amazon, useful thing to have in general) marine grade lugs. Little bulky, but that would definitely solve a large bit of esk8 fires…

Post a pic of the battery and wiring if you need more clarification

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I remembered what you did :joy::joy:

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I’ve admittedly never had this conundrum. Up till now have just fused the positive side from charger that goes straight to the battery :man_shrugging:

Having a fuse anywhere in the circuit is really all that matters in the end. Better than none.

The whole close to the battery thing is important in things like real car audio. Bigass 2/0+ cables carrying some massive load across distances. Further away the fuse is, more the wire heats up before the fuse pops. This can lead to the insulation catching on fire and causing the bay to also catch on fire.

And in the end, 99% of us will probably never have a situation in which a fuse will ever save us from something. Fuses in this are more for the really experimental shit in which you’re trying to make things that shouldn’t work work, and people going that far are already going to know to fuse their shit. I just think safety precautions for anything that could go wrong in DIY is pretty important, especially when it’s incredibly easy and not time consuming

I might actually be completely wrong and the positive charge is more ideal to be fused for precautions in direct LiPo/LiIon setups. I was mostly going off of Brian and my knowledge of car audio setups where there’s a ground to chassis.

Somebody else who isn’t me needs to come in with science. I don’t have the brain function for that

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in the interest of science…what was it?

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Stuck his multi meter probes in his charge port

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What are ya’ll doing with your charging ports to need protection… :joy: :joy: :joy:

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Lol in my brain I was supposed to take detailed photos of the fuse in place, doh! Anyway, here are the not-requested-photos…


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Simple 10A axial fuse. Super tiny. The connector is XT30 and the wire is 20AWG to give you a perspective on the size.

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Hi guys,
Quick question, would a 10a 32V fuse work for a 12s battery ( 50’4V) for the charging port? I have some around
My charger is 4a
Thanks

I think the answer is “most likely”

Fuses are meant to work up to their rating, so if you had a DC 250V 10A fuse, it’d work for 50V.

In cases where the fuse is rated for a lower voltage, the risk is that it’ll arc after failing and won’t actually cut power.

Since this is a relatively low voltage application, the arcing bypass isn’t as big of a concern (again, relatively speaking). Shorting the charge port and getting 100+amps to blow an out of spec 10A shouldn’t be too hard.

*this is all speculation based on some whitepapers, so my recommendation would be to use what you have if it’s what’s on hand and order some properly rated fuses to replace them later.
Input from anyone with off label use experience would be better, empirically.

Alternative option if you have piles of the fuses lying around is to test a couple yourself and see if they blow as expected at higher voltages.

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I currently have a 58V 7.5A fuse on a 12s battery…would that same fuse work on a 10s or would a 48V 7.5A work better for 10s?

they should work identically on the 10s.

I wouldn’t have any qualms using the 58V if you already have them on hand

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@Zach do you have an rs online link for one of these?

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https://www.mouser.com/Circuit-Protection/Fuses/Automotive-Fuses/_/N-ba8b5?P=1z0x8fvZ1ylo5uu
I found mines in here, they are cheap, not the shipment though…