# Wrong Fuse ... is 160VDC good enough?



## Zappo (Sep 1, 2011)

Although the 160VDC fuses would probably be okay, I don't think I would chance it. I did a quick eBay search and found plenty of the 300VDC fuses you are looking for at less than what you would pay for the 160V one. Don't know if you do eBay but I even found one listing that had three of the fuses with a "buy it now" of $49.


----------



## EVfun (Mar 14, 2010)

It is likely fine because you won't be over 160 volts when the current is over 400 amps. I can't recommend it because best practice is to use a fuse with a voltage rating that will never be exceeded by the equipment it is protecting. It is your call.


----------



## lowcrawler (Jun 27, 2011)

So a higher voltage no-name ebay fuse is better than a good one at it's limits?

(honest question, not trying to challenge)


----------



## Zappo (Sep 1, 2011)

lowcrawler said:


> So a higher voltage no-name ebay fuse is better than a good one at it's limits?
> 
> (honest question, not trying to challenge)


There might be some low quality "no-name" fuses out there but I haven't run into them. These are industrial fuses. I'm an industrial maintenance manager. Most of the brand I saw on eBay are the same brands I use all of the time.

Also, the voltage rating for a fuse is to ensure that it doesn't keep arcing across the gap when it does blow. DC is much more likely to sustain an arc than AC. That is why the voltage ratings are always lower. I've seen that happen a few times. It isn't pretty. It is just like not having a fuse in the circuit at all.


----------



## EVfun (Mar 14, 2010)

lowcrawler said:


> So a higher voltage no-name ebay fuse is better than a good one at it's limits?
> 
> (honest question, not trying to challenge)


I would avoid no-name fuses. Is that voltage rating AC or DC? Even if they state it is DC, what is the interrupt rating? What certifications (UL, ETL, CSA, CE, or...) does it have? Is there a solid company standing behind the ratings?


----------



## Coulomb (Apr 22, 2009)

EVfun said:


> It is likely fine because you won't be over 160 volts when the current is over 400 amps.


Yes, but in a fault condition the current won't be under 400 A; it will be what the battery can supply, which will probably be over 1000 A. So I don't think that logic like that is valid.

You want a fuse that can protect against a short circuit while charging the pack (the worst case for pack voltage), so it needs to be able to break 172 V at 1000+ amps. To me, that means that 160 V fuses are not adequate.


----------



## EVfun (Mar 14, 2010)

What is the battery pack voltage at 1000 amps? I'm pretty sure it will be under 160 volts. If the current is under 400 amps the fuse isn't supposed to do anything but imitate a piece of wire. 

For years the A13X series of fuses where used in Curtis powered EVs. These only have a 100 volt DC rating with a 10,000 amp DC interrupt rating. I do not recommend this. Please replace it with at least a A15QS series fuse with a 150 vdc rating. It will bolt into the existing fuse holders. Unless you really gotta fit a restricted space, or some existing fuse holder you can't replace, it would be better to fit a 300 volt fuse.


----------



## Coulomb (Apr 22, 2009)

EVfun said:


> What is the battery pack voltage at 1000 amps? I'm pretty sure it will be under 160 volts.


Good point. But I think that as the arc is just about to quench inside the fuse, the current falls, then the voltage rises again and it could be enough to sustain the arc because the fuse doesn't quite have enough clearance. Just 10 amps can sustain an arc that has plenty power to start a fire. I would not risk it.


----------



## lowcrawler (Jun 27, 2011)

Sounds pretty unanimous. 

Darn higher voltage. I really kind of wish I'd just gone with more AH on a 120V system... so much stuff is available at 120V (DC) that is either not available or much more expensive at 150V. Bah!

... but everyone said 'more voltage is always better!!!' so I listened.... We'll see if that proves true in the long run.


----------



## Coulomb (Apr 22, 2009)

lowcrawler said:


> Darn higher voltage. I really kind of wish I'd just gone with more AH on a 120V system... so much stuff is available at 120V (DC) that is either not available or much more expensive at 150V. Bah!


You call 158 V high voltage? 

You should see the problems we've been having with a 750 V (228 cell) system. For example, we decided on two 1000 V fuses:










From http://forums.aeva.asn.au/forum_posts.asp?TID=980&PID=26967#26967 (Coulomb and Weber's MX-5).


----------



## lowcrawler (Jun 27, 2011)

Okay -- seriously... now I'm getting pissed off. I bought another class T fuse. (Edison).

So now I have a fuse block than says "FOR CLASS T FUSE".

... and I have CLASS T FUSE written on the fuse.

But it doesn't fit, not even close. In fact, it seems the exact same size as the one I had before.

What the hell? Can someone teach me what I need to know before I blot a bunch more money?


----------



## lowcrawler (Jun 27, 2011)

Okay, so I need a different fuse block, perhaps?

Does anyone have anything cheaper than this: http://www.grainger.com/Grainger/LITTELFUSE-Fuse-Holder-6MUW2

?

188 bucks for a fuse holder... seems way out of line expensive, no?



This: http://www.grainger.com/Grainger/FERRAZ-SHAWMUT-Fuse-6UVF6?Pid=search

is the fuse I have. Can anyone point me to the appropriate (covered) fuse block?


----------



## major (Apr 4, 2008)

lowcrawler said:


> Okay, so I need a different fuse block, perhaps?
> 
> Does anyone have anything cheaper than this: http://www.grainger.com/Grainger/LITTELFUSE-Fuse-Holder-6MUW2
> 
> ...


Hi low,

http://www.discountfuse.com/P243G_p/p243g.htm 

Double check for suitability for your fuse. Also the P266C might work. You'll have to devise your own cover. But these blocks go for about $50 retail.

major


----------



## dladd (Jun 1, 2011)

you are working way too hard here. I just clicked on a vendor at the right of this forum, and found this. Fuses and fuse holders already selected by an electric vehicle vendor. I'm sure other EV shops carry similar stuff, if you already have a favorite you buy stuff from. Why not support those in the industry? Prices seem fine too.


----------



## dladd (Jun 1, 2011)

lowcrawler said:


> This: http://www.grainger.com/Grainger/FERRAZ-SHAWMUT-Fuse-6UVF6?Pid=search
> 
> is the fuse I have. Can anyone point me to the appropriate (covered) fuse block?


sorry i didn't see the 'covered' requirement before. Anyway, here is a covered one from another EV vendor.


----------



## major (Apr 4, 2008)

dladd said:


> sorry i didn't see the 'covered' requirement before. Anyway, here is a covered one from another EV vendor.


They say it fits, but I have doubts


----------



## lowcrawler (Jun 27, 2011)

Given that LOOKS like the block I already have -- and that fuse block manufacturing company doesn't appear to make a fuse block that fits my fuse -- I sent them an email.

I did look at EV shops before looking elsewhere... and other than there (where I have a query in to) I don't see any.


----------



## EV-propulsion.com (Jun 1, 2009)

"_They say it fits, but I have doubts_ " 
Yes a A30QS does fit on this holder and does fit under the cover (just). One caveat, with some lugs the fuse leg ends and/or lug need to be filed so there is no interference with each other. 
Btw, we found the ferraz-shawmut holder pretty flimsy, where the fuse mounting bolts are 5/16", a little small for the groove in the fuse. Personally I also don't like to use the fuse mounting stud to attach the cable (seem to always get some loosening)
but I am sure there are plenty in use like that.
Mike
www.EV-propulsion.com

Edit: I just checked, they both use 5/16" studs, but the ferraz shawmut holder does not have a flat surface for the fuse to sit on and relies on washers to rest on.


----------



## major (Apr 4, 2008)

EV-propulsion.com said:


> "_They say it fits, but I have doubts_ "
> Yes a A30QS does fit on this holder....


Yep, I guess so. Pretty close to those outside terminals. And I never used the P234G but that was recommended on the fuse spec sheet. I have used many of the P266C and they are quite sturdy with 3/8" studs and 5/8" heavy hex nuts that securely clamp the fuse tab to the cable lug.


----------

