## Anyone know of good compact DC fuses?

### VDC (Voltage DC) vs VAC (Voltage AC) - Fuses

While searching for DC fuses, I was dismayed at the limited selection of DC fuses.
Most fuses seem to be rated for AC current while most ebikes, use DC current.

So, I decided to investigate the mathematical relation of AC to DC voltages, as pertaining to fuse ratings.
Most basic fuse types are usable, for AC or DC, but the voltage is rated differently.
Fuses with dual ratings, were very rare but ...
Determined from Buss, (Bussmann), fuse ratings, DC volts, is approximately 2/3 the AC volts.
For example, the same fuse is rated as 80V DC 200a and 125V AC 200a.
Amperage is listed, as same, but DC voltage is about 65% of the AC voltage.

From AC, multiply the voltage by .65, to determine the DC voltage.
A 220VAC 100a fuse would be nearly "spot on" for a 144VDC 100a build! (220V x .65 - 143V)
A 110VAC 100a fuse would be nearly "spot on" for a 72VDC 100a build! (110V x .65 - 71V)

From DC, multiply the voltage by 1.55, to determine the AC voltage.
If you want a 100VDC 200a fuse, a 155VAC 200a fuse would be perfect, 150VAC fuse, should do.

Basic fuse function: While Amperage is reasonably critical, matching voltage is much less so!
But, the rated voltage should be higher than the working voltage!
110VAC fuse, (110V x .65 = 71.5V), should not be used for an 80VDC build!
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DrkAngel
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### Re: Anyone know of good compact DC fuses?

fechter wrote:I wonder if you could stick a strong magnet to one of those automotive fuses to make a magnetic blow out?

This is a great idea!.. just like some contactor and relay have!

This have to be tested!!

I will test that this week!

I recall that i often blown these 32Vdc ( 12V car) little fuse with my controller blowing up and i never had any fire... the worst that happened was that the plastic of the fuse vaporized and left a black coated stuff inside the fuse protector...

I saw more bad fuse connections making fuse to melt than fuse catching fire!.. the fuse terminal that connect to it MUST be able to sink the heat otherwise the plastic just melt... The only location that can heat is the little filament right onthe center of it. I already saw one fuse that was so melted than the two terminal was touching together and the fuse was no more a fuse... but a conductor!

So the terminal that connect to the maxi and normal fuse ( the one up to 40A with the orange color) must have proper connection with minimal resistive loss and must have the proper wire size to sink the heat... just like the anderson connector spec data are specifying!.. fuse also have ingineering !

Take a look of the 100A+ blade fuse terminal block!.. they are heavy and can sink the heat and share the current with the proper uniformity to only allow the melt or heating spot to happen on he right spot.

If the fuse have too much heat on his terminal, the spec current become derated and it will probably blow at lower current than the specified one. This also change alot the delay.

Doc
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### Re: Anyone know of good compact DC fuses?

The problem with DC and fuses apparently is arcing/plasma. With AC, the voltage will pass through 0 and extinguish any arc. With DC, the arc can form and stay, current still flows through the fuse if it's not properly designed. I wouldn't thrust any extrapolation of DC voltage from an AC-only rated fuse, it's more than that.
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### DC Voltages "De-Rated" to Factor DC Arc Length

I would guess, that is why the DC voltage is de-rated.
Voltage ratings are factored, partially, by the possible arc length.
Reducing the rated voltage, should reduce, possible DC arcing, to comparable with the higher AC rated voltage.
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There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

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DrkAngel
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### Re: Anyone know of good compact DC fuses?

Maybe this ll be a good option.

http://www.discountfuse.com/A3T100_p/a3t100.htm

By the specs they would take a little while to blow, what you guys think?
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### Re: DC Voltages "De-Rated" to Factor DC Arc Length

DrkAngel wrote:I would guess, that is why the DC voltage is de-rated.
Voltage ratings are factored, partially, by the possible arc length.
Reducing the rated voltage, should reduce, possible DC arcing, to comparable with the higher AC rated voltage.

My guess is DC voltage is de-rated because of heat. 0.707 is the constant to get RMS from sinusoidal ac; not that far from 0.65. But just a guess anyways.
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### Re: Anyone know of good compact DC fuses?

gensem wrote:Maybe this ll be a good option.

http://www.discountfuse.com/A3T100_p/a3t100.htm

By the specs they would take a little while to blow, what you guys think?

If you have the time and patience, to investigate all the types, then here is the place to hunt, for exactly what you want. Bussmann
Each product has "Data Sheet" specs & (some), "Time-Current Characteristic Curves—Average Melt"

For example, check this item.Drive Fuse High Speed Fuses Check the "Data Sheet"!
Higher voltage rating than necessary, but that only hurts your wallet, nothing else.
Sorry ... probably larger than requested.

Personally, I got a bit "lost", hunting through all the different "types", specs & profiles.
But I wasn't hunting for something to fit my specific needs.

Personally, I liked the ANN & ANL Limiter-Fuses Top voltage rating is 80VDC, which is OK, for my present builds.
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Last edited by DrkAngel on Tue Feb 21, 2012 8:57 am, edited 1 time in total.
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DrkAngel
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### Re: Anyone know of good compact DC fuses?

Luke, I don't think you're going to find anything smaller than what you have there. That said, I think cooper Bussman has some really nice competitive products to that:

http://www.cooperindustries.com/content ... pj-sp.html

grindz145
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### Re: Anyone know of good compact DC fuses?

I like these. you can get them in 60a - 100+a from 125V and up. They are pretty small, only 3/4" wide. I use them as a fuse and battery disconnect along with a cap. precharge resistor.

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nicobie
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### Re: Anyone know of good compact DC fuses?

Good one Nicobie!
But they are charging 112 dollars to ship one to Brazil.
A decent 25mph bike will cost around \$1000.
A decent 35mph bike will cost around \$2000.
A \$1000 35mph bike will get you killed.
Justin we really appreciate what you did!

gensem
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### Re: Anyone know of good compact DC fuses?

Good find. I ordered one.

I also ordered this one: Blue Sea Systems 7250 C-Series Toggle Single Pole, rated for 80vdc 100a.
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ryan
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### Re: Anyone know of good compact DC fuses?

DrkAngel wrote:Couple possibilities.
Bussmann ACK-200 Fuse. 200 Amp, 72 VDC, Dual Element.

So I got this fuse today. Boy is this thing huge. Looks like its going back on eBay. Anyone want it?
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ryan
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### Re: Anyone know of good compact DC fuses?

How big is it? It looks like it'd be at least as big as my thumb....

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### Re: Anyone know of good compact DC fuses?

Try an iPhone.
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ryan
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### Re: Anyone know of good compact DC fuses?

The "ANL" looks a bit more reasonable ... size, about 1" x 3", but fairly flat.
Limitation is 80VDC ... that I've seen ...
Bussmann ANL series - specs and chart

Importantly, to some, is the wide variety of ANL fuse holders, apparently this fuse style is popular for vehicle audio systems, so there is an assortment of "pretty" ANL fuse holders.
Many "cheap" ANL fuses intermingled with fuse holders, be sure to confirm rated voltage!
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There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

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DrkAngel
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### Re: Anyone know of good compact DC fuses?

We ought to see what fuses the big Sevcons use that are rated up around 115 V. Might pick up some cost effective ideas.
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### Re: Anyone know of good compact DC fuses?

ryan wrote:Try an iPhone.

Ok, that *is* big.

Largest one I have held in-hand is an old (unfortunately blown) JKS-250, and though it is bigger than yours it is not by all that much:
DSC06127.JPG (41.89 KiB) Viewed 562 times

I'd guess at 2-3lbs or more for weight, without trying the scale. 600VAC 250A, can interrupt up to 100,000A.

But this isn't helpful to the discussion at hand...sorry.

I only bring it up because I have considered opening it up and rewiring it using thin solder or the like, since in a dead short at least I know that would melt before the rest of the system caught fire or something, if I had a really huge battery setup on a bike or whatever. I believe it uses sand or similar inside, so that during an extreme event it melts the sand into glass to close the current path.

bigmoose wrote:We ought to see what fuses the big Sevcons use that are rated up around 115 V. Might pick up some cost effective ideas.

I found a number of "Sevcon fuses" in a search, but am not sure which ones would be useful to us. Very few have pictures or useful information. Prices vary a lot, too.

Sevcons like this one:
http://www.electricmotordepot.com/sevco ... 0v-350amp/
are using a fuse I don't know the type name for, but it is visible on the controller as the white "bar" with end tabs below:
G2445__67435_zoom.jpg (13.92 KiB) Viewed 562 times

I assume it would be rated over 100VDC / 350A as the Sevcon itself is.

I have smaller versions of these fuses, labelled as "mega fuse", from huge APC UPS's external battery packs and from powerchairs (both of which also used SB50 Andersons, oddly enough). Mine are rated at 100A, and probably 24-48V at a guess, but I can't remember just now, and don't have them handy to check. Been considering digging them out for installation into my packs on the bike, but all the tuits I have here are non-circular.

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### Re: Anyone know of good compact DC fuses?

Pictured Sevcon is a 72-80V.
Wrong - It appears to use a Shawmut CNN Series fuse, which is rated as 130VAC - 80VDC. - Wrong
The Shawmut CNN cross references as the Bussmann ANN Series.

Tis a "Littlefuse" 80 amp DC rated.

MEGA vs ANL
"MEGA" and standard "ANL" are both rated as "48VDC max"
Last edited by DrkAngel on Wed Mar 28, 2012 9:48 am, edited 2 times in total.
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DrkAngel
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### Re: Anyone know of good compact DC fuses?

I believe that fuse has been pictured in this thread earlier. I bought mine from Digikey or Mouser.

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### Re: Anyone know of good compact DC fuses?

littlefuse 80VDC - click on picture
Littlefuse.jpg (75.34 KiB) Viewed 544 times
A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

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DrkAngel
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### Re: Anyone know of good compact DC fuses?

The problem remain... fiding a fuse OVER 80VDC , that is cheap, small enough and accessible!

Doc
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### Re: Anyone know of good compact DC fuses?

Doctorbass wrote:The problem remain... fiding a fuse OVER 80VDC , that is cheap, small enough and accessible!

Doc

125 VDC, 90A, \$17, aprox 2" x 3" x 3/4" mounts almost anywhere and can be used as a main battery disconnect too.

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### Re: Anyone know of good compact DC fuses?

Doctorbass wrote:The problem remain... fiding a fuse OVER 80VDC , that is cheap, small enough and accessible!Doc

Doc, that is why I was interested in what Sevcon did for their controllers that are rated over 100V. When I look at the spec's they talk about like rated 80V but then say:
Conventional working voltage 50.4 to 96V
Working Voltage 39.1 to 116V
Non Operating over voltage limits 132V

Now they may be playing a bit of requirements chess with respect to controller/fuse ratings. However, it appears if there was "really a problem" with an 80V rated fuse at say 96 and 116V, Sevcon would change the design, assuming they use that 80V rated fuse. I wouldn't use a 48V fuse at 116V, but what about an 80V DC rated fuse at around 100 and change?
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### Re: Anyone know of good compact DC fuses?

Oops!
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Last edited by DrkAngel on Sun Feb 26, 2012 3:56 pm, edited 3 times in total.
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DrkAngel
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### Re: Anyone know of good compact DC fuses?

They simply call it an 80v controller to get around the 80v fuse limitation.

Even at 66v, testing various ANN type 80vdc fuses, the normal method of blowing involves exploding the quartz window out and melting with plasma through any plastic materials around it. It's also interesting that the 425amp ANN fuse actually peaked over 6,800amps before it popped.

It is the very wrong assumption to make that these high current DC fuses will offer anything in the way of protecting your electronics from over-current related failures. They are to avoid cabling/battery fires, and nothing more.

In the case of a Sevcon, the fuse is there to protect the battery and cabling from fire if the controller somehow faults into a shorted input condition. The fuse offers no protection for the controller itself.
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