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Battery post fuse


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I have been concerned for some time that my battery feeds have no fuses. Some threads on here went into this  in some detail .Island Time especially been quite blunt about it! I found it not that simple to retro fit a fuse  as finding a place to mount them and then measuring up for remaking the HT leads at an auto electrician , . They are fat welding cables. While at Jaycar today I found these;

 https://www.jaycar.co.nz/battery-terminal-fuse-200a/p/SF4184

Problem is I couldnt figure out how they worked and neither could the 2 guys who worked there!

It appeared to need an insulated washer under the bolt head  thats not supplied. 

So, once I get that sorted is this a way to go? I think there biggest is 200 amp which should do starting a Yanmar YSE12?

My 12 volt bible is a book called Caravan and Motorhome electrics by Collyn Rivers who says fuses shouldnt be in battery boxs. I guess thats because if a fuse blows it might blow up the battery box! I think I will take that risk.

 

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Yep, they work fine, and are IP (ignition protected) rated - as they must be in a battery enclosure. They just make the battery a bit taller, and they have to fit.

Don't rely on automotive electrical advise. They don't have to deal with the corrosion issues that a boat has. I'd recommend Nigel Calders book  - see https://www.amazon.com/Boatowners-Mechanical-Electrical-Manual-4/dp/0071790330?SubscriptionId=AKIAILSHYYTFIVPWUY6Q&tag=duckduckgo-d-20&linkCode=xm2&camp=2025&creative=165953&creativeASIN=0071790330

Those fuses are cheap - probably crap. Proper ones, like the Bluesea ones, are really IP rated and available up to 300A about $40 each IIRC.

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Further to that - you need the post fitting, not an insulation washer! 

From Bluesea;

DESCRIPTION

 

  • Requires the use of Terminal Fuse Blocks PN 5191 or PN 2151 - do not mount the fuse directly to the battery terminal.
  • Interrupt rating satisfies ABYC requirements for DC Main circuit protection on large battery banks.
  • Ignition protected - safe for installation aboard gasoline powered boats.
  • Clear window - visual indication of blown condition.
  • Colour coded for each amperage.

Installed like shown in that Jaycar link they simply would not work. The bolt is in contact with the battery terminal and the cable lug....

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Each to their own, I use the Bluesea unit IT linked to, Works fine. The pic above can't mount to the battery directly tho so you still have a risk of upstream being unprotected.

 

However if cost is a concern and you can accept that risk you have these:

https://www.lusty-blundell.co.nz/product/1842-blue-sea-mega-amg-fuse-block-100-300a-with-cover?categoryId=928

 

Along with the fuse:

https://www.lusty-blundell.co.nz/product-group/8103-blue-sea-fuse-mega-amg/product

 

For under $80, A bit less than the $120 for the proper battery mount

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Big difference $4.50 to $40 plus a post fitting. Well thats yachting Thanks for the info.

Yep, but it costs the manufacturers to have the gear IP rated and ABYC certified. IMO a cheap one, likely to spark on blowing, and therefore an ignition source, does not reduce your risk at all. If it's worth adding, use good gear.
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Ignition source sparking from a circuit breaker on a lead acid battery....  is a very good reason NOT to have post mounted fuse or circuit breakers. Run sensible cables to an area outside your vented battery enclosure.... and then use your breaker system of choice. There are very few volatile vapor sources on a yacht. Potentially one of the most explosive is the battery system. Most yachts dont have inboard petrol motors. Ignition protected starter motors and alternators etc are actual not needed (or legally required for survey in a diesel installation. That leaves your Gas locker. ...your outboard fuel storage...and all those nasty little cans of cleaning and lubricating bombs........  mayee dont put your circuit breakers near those either  :idea:  :)

oh and by tha way... dirty battery terminals can generate enough heat if running a high load like a starter motor, anchor winch or bow thruster to melt the battery post clean off....

just some perspective..

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Personally I do not like Fuses. They are final. I have the view that when it all goes to custard, it is likely at the worst possible time. You need to be able to isolate the fault and get power back up ASAP. A Circuit breaker is the better idea than a fusible link that needs to be physically replaced. Plus, fuses work by failing at the maximum current point. That is fine when a dead short takes place. But for situations like say Starting, that link gets hot and current is wasted across it. A circuit breaker, if it is any good, should not have that happen.
Which brings me t the next point. There are good circuit breakers and bad ones. DO NOT use a breaker that triggers by heat. Common in cheap types of breakers. Instead, magnetic breakers are the better. They pass all current cleanly with no heat till they reach their trip point and then trip.

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Yes replacing a post fuse wouldn’t be that simple or quick , getting the box cover off Is a bit of a mission in itself, mind you if the fuse is blown there’s bigger problems elsewhere! How would a magnetic breaker work if not heat?

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On our boat we only have 1 set of fuses, On the battery terminal, from there we run 25mm cable inside conduct to our distribution point where we have a setup with a BlueSea 100a breaker feeding Schneider iC60 breakers sized for the downstream wire runs. If our terminal fuse pops the problem is not going to be simple to fix so the time to change out the fuses doesn't matter, We would have to be having a cable fault to blow the fuse

 

Always get Ignition proof fuses, It's a no brainer. You really dont want any section of your electrical setup unprotected especially if your not going for the super duper tinned cable/twin sheathed/oil resistant stuff, Your battery should be a bolt type post too, Yes dirty terminals can cause heat but bolt type posts cleaned and installed can't really get dirty/poorconnection like the standard post types

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Installed looks like this;

e86dc5aa4d8c0fc197a160bb4fca845bcb0862b4

So I just went through this. Jaycar only had fuses up to 200A and didn't sell the posts. Got the posts from Lusty Blundell in Albany who only had 100A fuses. So back to Jaycar for the fuses. Turns out the Jaycar fuses won't fit on the posts, the ceramic is just too small so had to stack a 1mm stainless washer under the fuse so it made contact with the post.

 

Havn't been able to source a 300A one yet.

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So I just went through this. Jaycar only had fuses up to 200A and didn't sell the posts. Got the posts from Lusty Blundell in Albany who only had 100A fuses. So back to Jaycar for the fuses. Turns out the Jaycar fuses won't fit on the posts, the ceramic is just too small so had to stack a 1mm stainless washer under the fuse so it made contact with the post.

 

Havn't been able to source a 300A one yet.

The stainless ones will cause a lot of heat and resistance. I made some copper washers and they have worked well as a temporary fix till we got back to NZ to find the proper fuses.

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