# Using DIN or fuse block holder in vehicle?



## Nabla_Operator (Aug 5, 2011)

High Voltage DC is a problem for small wired glass fuses, Sabathom, because the spark doesn't extinguish (keeps conducting even when the wire is melted). I once made a choice between:


this 1 EURO fuse holder and
this 2 EURO fuse holder. Both qualify for 500 VDC.
But it is much more difficult to find matching fuses:


5x20 mm (not found)
1/4 x 1(1/4)" (Siba, example).
An option may be the NH00 fuses (same price range as J-class)
Good luck, keep us informed,
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## sabahtom (Mar 1, 2011)

Thanks Nabla_Operator.

Any thoughts about using DIN fuse holders though? There is this one that is about $7 and has screw-type terminals. should be tough enough for auto use, or not? evsource sells them too I see. I think I'll give them a go.

 http://www.evsource.com/tls_fuse_holders.php

http://my.element14.com/jsp/search/productdetail.jsp?sku=248757


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## sabahtom (Mar 1, 2011)

*AJT confusion*

This link says the AJT5 is 57mm x 21mm.

http://www.ferrazshawmutsales.com/pdfs/AJT.pdf

This link says the holder US3J1 is the right size, but I thought AJT5 fuses were 38x10mm? Maybe too late at night, time for bed.

http://www.discountfuse.com/AJT5_p/ajt5.htm
*
*


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## EVfun (Mar 14, 2010)

*Re: AJT confusion*

I don't know if it is really advised or not, but I have used DIN rail fuse holders and DIN rail relay sockets in EVs before. I didn't have any problems with them. 

If possible I'd get the fuses and fuse holders from the same source. They can verify that you are buying matched parts that way.


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## evmetro (Apr 9, 2012)

I have found that my 300v shawmut fuses fit quite well in AGU fuse holders. The car audio industry offers all kinds of fancy AGU holders, many of them are way overkill. I don't know if your 600v fuses are the same dimensions as my 300v ones, but if they are, it could be worth a look. I would not be surprised if the car audio AGU holders are only rated for 12 volts, but a lot of them look like you could run enough juice through them to run a big controller. The ones I use for my 300 volt shawmuts are way nicer than those black plastic ones with the screw terminals.


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## sabahtom (Mar 1, 2011)

I'm looking at a local supplier because the shipping tends to be 4 x the item price off ebay. Seems that only Americans sell fuses 

For my charger cables, I think this will work? There should not be major surges in the current there.

http://malaysia.rs-online.com/web/p/cartridge-fuses/3618193/


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## Nabla_Operator (Aug 5, 2011)

Siemens Diazed fuses (5SA, 5SB) are the common household fuses for 100 years now and they are rated for 500 VDC. From 2 Amps on. DIN rails fuseholders are available too.

DIN-RAIL... I don't like the rail solution in a vibrating car. Rails are for mounting components in steady cabinets. In your car, every component will be tipping on the rail untill something breaks off. 

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## Tesseract (Sep 27, 2008)

The key to using common 5x20mm fuses in DC circuits is to ensure the source resistance is high enough to limit the peak current to what the fuse datasheet says it can interrupt. For 5x20mm fuses at 400VDC, the interrupt current rating is usually 500A, but can be as high as 1500A (for the ceramic body style.

So if you have a 350V pack and the fuse has a 500A interrupt rating the source resistance needs to be at least 350V/500A = 0.6Ω.

Now some of this resistance will be in the wiring, inside the cells of the battery pack, etc., but even still you will need to add some series resistance (say, at least 0.39Ω) and the losses in that resistor will rapidly increase to the point of being impractical above a couple amps or so of continuous load current, at which point you might want to consider a 3AB series ceramic fuse (usually good for 600VDC and with a 10kA interrupt rating).


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## sabahtom (Mar 1, 2011)

Nabla_Operator said:


> Siemens Diazed fuses (5SA, 5SB) are the common household fuses for 100 years now and they are rated for 500 VDC. From 2 Amps on. DIN rails fuseholders are available too.
> 
> DIN-RAIL... I don't like the rail solution in a vibrating car. Rails are for mounting components in steady cabinets. In your car, every component will be tipping on the rail untill something breaks off.
> 
> ---


Looks good except I already bought the other ones...at about triple the price. Thanks for the info though, I might still end up buying them. I'm putting them in a tight box so I don't think there will be much movement but I'll double-check it.


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## sabahtom (Mar 1, 2011)

Tesseract said:


> So if you have a 350V pack and the fuse has a 500A interrupt rating the source resistance needs to be at least 350V/500A = 0.6Ω.


Thanks very much for taking the time to write that, Tesseract.

My pack is 97 x 3.5v (I don't plan to charge higher than that) = 340v.

The AJT15 fuse has 100KA interrupt rating. I wish I'd known about these Siemens fuses before I started my build, at least to consider them. By the calc below it looks like I may have ended up with AJT fuses or something similar though.

My cells are supposed have 2 milliohm IR.

3.5v / 0.002 = 1750A. 

That's safe I guess - but today while charging at 12A this AJT15 fuse was already getting warm. The Siemens household fuses mentioned above have a max ambient rating of 40 celsius. It's likely that my fuses will be near or over that every day. 

_The key to using common 5x20mm fuses in DC circuits is to ensure the source resistance is high enough to limit the peak current to what the fuse datasheet says it can interrupt. For 5x20mm fuses at 400VDC, the interrupt current rating is usually 500A, but can be as high as 1500A (for the ceramic body style._


My multimeter is not great, I'm not sure I'd trust it to deliver this kind of precision where I need the results to size a fuse.

Any thoughts?


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