400A 160VDC T-Class Fuse Holder Melted

[mwcolo]

Had this 400A 160VDC T- Class fuse and holder on my negative lead attached to 4/0 copper cable for about 6 months. This is on my 30kWh battery bank, 48V. Regularly charged at 8kW with max DC current around 175A (really it's less since charging voltage is max of about 57V).
Worked fine, though got fairly warm, until a couple days ago when the inverter thought there was no longer any battery.
The plastic backer, to which the fuse lugs were attached as an insulating standoff to the fuse holder body, melted on one side. Perhaps I'm wrong about the regular capability of this fuse and its rating? I'm just glad it didn't start a fire.
Anybody have a suggestion of what kind of fuse and holder would be rated for my battery bank? Max the inverter can push or pull is 185A.

 

[TacomaJoe]

That has all the look of a poor connection (discolored bolt). It heated under load, melted some plastic and got worse. How tight is that nut on the fuse?

 

[Lt.Dan]

Definitely a poor connection. No other way to build heat, especially enough heat to melt plastic.

Good quality connections shouldn't get hot. Warm, yes, but not too hot to touch or anything.

 

[Rocketman]

The copper(?) plate below that conducts the current looks rather small- at least compared to my Blue Sea ones.

 

[Hedges]

Airtight box around a fuse doesn't seem good, would like venting.

Although you have a box covering exposed contacts, there are exposed bolts. Commercially made fuse holders have the bolt heads recessed so at least not sticking out. (edit: Oh, maybe that fits inside the box so not exposed.)

It appears you have a sheet of plastic in the compression path between nuts. That will relax and relieve contact pressure.
If you put a nut on top of the plastic, then busbar followed by fuse (or cable terminal) then a third nut ... that would clamp the contact between metal nuts. No plastic to compress, creep, soften and ooze out.

Such assembly may give you trouble with cable's ring terminal colliding with fuse, because busbars are too short. So you may end up just stacking fuse directly on terminal. Which at least gets away from the concerns about busbar cross section (and metal).

 

[Zwy]

That was a connection with resistance, most likely caused by becoming loose over time.

 

[JRH]

View attachment 153060View attachment 153061
Had this 400A 160VDC T- Class fuse and holder on my negative lead attached to 4/0 copper cable for about 6 months. This is on my 30kWh battery bank, 48V. Regularly charged at 8kW with max DC current around 175A (really it's less since charging voltage is max of about 57V).
Worked fine, though got fairly warm, until a couple days ago when the inverter thought there was no longer any battery.
The plastic backer, to which the fuse lugs were attached as an insulating standoff to the fuse holder body, melted on one side. Perhaps I'm wrong about the regular capability of this fuse and its rating? I'm just glad it didn't start a fire.
Anybody have a suggestion of what kind of fuse and holder would be rated for my battery bank? Max the inverter can push or pull is 185A.

that plastic base is odd looking….what brand was the fuse holder.….???

 

[HRTKD]

I believe that my Blue Seas Class T holders come with lock washers. I don't see any lock washers on that fuse holder.

 

[Mattb4]

Most of these will have a washer and lock washer. I am with TacomaJoe on how that failure occurred.

 

[JRH]

I believe that my Blue Seas Class T holders come with lock washers. I don't see any lock washers on that fuse holder.

Here’s the two type blue seas most people have…see pic. …5502 &. 5007 and they don’t look anything like whatever that is … your right they come with lock washers… ( but I went with nylock) Not right or wrong ,just a personal preference.
with the prices and scarcity of good classT stuff in the last two years, I had a feeling new stuff would make an appearance…

 

[mwcolo]

Based on your comments, looking at the Blue Sea fuse holders, and swapping out with an identical one but limiting the current to 85A, my conclusion is that this thing is junk and I got what I paid for.
The fuse itself actually gets quite warm despite seeming like it's good quality. The "legs" on the fuse are tinned copper, but not sure if they should be thicker for the expected current.
Apart from that, the extension metal is thin and not copper (not sure what it is) and when bolted in with the supplied nuts and single washer, doesn't provide much contact with the wire lugs. Additionally, with the design of the plastic standoff, even though I torqued the bolts down pretty tightly, it seems that the heat may have made the plastic less rigid. Because the tightness is dependent on the rigidity of that plastic sandwiched in between the bolt head and nut, it seems it would loosen when heated even if a lock nut were used.
I'm going to have to order a blue sea holder and perhaps find a better fuse. The fuse was significantly hot with 6.1kW (115A) charge rate, so I'm stepping it down further until I can replace it.

 

[HRTKD]

I'm going to have to order a blue sea holder and perhaps find a better fuse. The fuse was significantly hot with 6.1kW (115A) charge rate, so I'm stepping it down further until I can replace it.

Good plan.

 

[mwcolo]

that plastic base is odd looking….what brand was the fuse holder.….???

Unbranded Amazon special. Came as a package of holder plus fuse.

Here's the link so others can avoid.

Class T Fuse Block Holder, 160VDC 400 Amp Fuse Holder Fits High Power Appliances in Inverters and Car Stereos Rvs Boats Cars Trucks https://a.co/d/7x9hoi0

 

[JRH]

Unbranded Amazon special. Came as a package of holder plus fuse.

Here's the link so others can avoid.

Class T Fuse Block Holder, 160VDC 400 Amp Fuse Holder Fits High Power Appliances in Inverters and Car Stereos Rvs Boats Cars Trucks https://a.co/d/7x9hoi0

Wow…. That ranks right at the top of the most misrepresented bunch of hogwash I have ever seen advertised.. Being as polite as possible , it’s awful and takes advantage of people in a culture that generally trust adds to be at least a little bit honest.
sorry you got duped man .
At least there is nothing wrong with making a mistake as long as one learns from it…
good luck with your system…
J.

 

[Zwy]

I purchased 4 of these for my battery bank, one for each battery. https://www.bestconverter.com/Class-T-Fuse-Block-175-Amp_p_217.html and also 2 300A to each inverter.

Don Rowe sells the same FB1 fuse blocks with the Class T fuse but everyone that handles the FB1's is out of stock. These are built like a tank.

 

[HRTKD]

Unbranded Amazon special. Came as a package of holder plus fuse.

Here's the link so others can avoid.

Class T Fuse Block Holder, 160VDC 400 Amp Fuse Holder Fits High Power Appliances in Inverters and Car Stereos Rvs Boats Cars Trucks https://a.co/d/7x9hoi0

Make sure you write a review and include your pictures.

 

[Hedges]

Class T Fuse Block Holder, 160VDC 400 Amp Fuse Holder Fits High Power Appliances in Inverters and Car Stereos Rvs Boats Cars Trucks https://a.co/d/7x9hoi0

Is that a nut under the ring terminal?
And about 10 awg terminal?

 

[efficientPV]

The bolts were tightened up against plastic. What a joke. No wonder it failed.

 

[HRTKD]

Is that a nut under the ring terminal?
And about 10 awg terminal?

The first image in the Amazon page? Yeah, it is! But that's a drawing, not an actual photo I think.

 

[JRH]

The first image in the Amazon page? Yeah, it is! But that's a drawing, not an actual photo I think.

As Gomer used to say, SMAME SHAME SHAME …on whoever would sell that kinda stuff.