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Eaton AMX and AMH Fuses alternative to Class T

yabert

Solar Enthusiast
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Québec, Canada
I think I found a really interesting 10-15$ fuse alternative to Class T fuses.
Eaton Bussmann AMH specs:
-current ratings 350A, 400A or 500A
-ultra-high interrupting ratings, up to 20,000 A.
-voltage ratings, up to 125 Vdc

Eaton Bussmann AMX specs:
-current ratings 80A to 350A
-ultra-high interrupting ratings, up to 8,000 A (63Vdc).
-voltage ratings, up to 125 Vdc

Look good to me. Any thought?

Eaton fuses.JPG
 
Looks like a plan but I’m not an electrician. I’ll be watching this to see what the thoughts are.
 
Considering those kind of fuse generally have increased breaking capacity as voltage go down (see pictures as example), could I consider the AMH fuses breaking capacity to be around 50 000A at 60V?
I ask because EV battery are othen very powerfull and there is no need for a large capacity to have very high short circuit current.

Anyhow, to me the small 10$ AMX fuse is awesome for e-bike/motorcycle battery and other small capacity batteries. It is really compact, I like it.

Fuse breaking capacity-1.JPG

Fuse breaking capacity-2.JPG
 
For comparison I had posted the trip curve of a JLLN class T fuse here:
And that ANH fuse below. Glancing at it looks like the ANH is a slightly slower tripping but doesn't seem significant for normal 48V battery application. i.e. sending double the current rating of the 350A ANH fuse shows 100 seconds whereas doubling the 200A class T fuse is around 70s

Screenshot 2023-04-06 at 8.34.56 AM.png
 
Here compare to A15QS fuse.
When comparing 350A fuse, it seem like the semiconductor fuse will blow at lower current, so a bit faster in a short circuit event.
I'm not concern about the 750A VS 1000A blowing current at 1 second, but I'm more concern about the 1100A VS 3500A blowing current at 0.01 second.
Fuse breaking capacity-3.JPG
 
...could I consider the AMH fuses breaking capacity to be around 50 000A at 60V?
I found this graphic specially useful to understand increase in braking current capability with lower voltage.
A typical 48V system will have a correction factor around 0.3 (circle in orange).
If I understand this correctly, the AMH fuse braking current capability rate 20kA at 125V should be around 60kA at 48V.

Of course, this is based on spec sheet of another fuse manufacturer, but it's quite similar to the Bussmann AMX capability who have a correction factor of 0.375 when voltage pass from 125V to 63V:

Fuse breaking capacity-5.JPG

Fuse breaking capacity-4.JPG
 
I ordered one 350 AMH fuse.
The compactness, the low price and the high interrupting ratings are just too attractive ?
I have hard time to believe the thickness of 0.6mm (only 0.023''). I hope it's an error.
0.6 x 17 is only 10mm2 or AWG 7 equivalent ?

Fuse breaking capacity-6.JPG
 
You get a bit more capacity when it's that spread out, but I agree that looks rather small for a 350A fuse. Hope that's for a smaller fuse, and the drawing is off a bit, otherwise that's going to sap a bit of power. I look forward to finding out what your calipers say about it when it shows up.
 
Nice compact little fuse.
Finally the thickness is actually two sheets of 0.012'' for a total of 0.024''.
Can you imagine, this one is rated at 3x nominal amps for 10 seconds so 1050A... I bet it is very hot after this kind of event.
Spec sheet say 0.14mohm so 154W of lost at 1050A :oops:
Ok, it only 17W of lost at 350A. Is it right? 0.00014x350=0.049x350=17W? Or resistance can change drastically at high temperature?
If it's right, I don't understand how a 350A T class fuse can be rated at 40W of lost at 350A :unsure:

Fuse AMH-350.JPG
 
Other interesting new fuses for the DIY stuff.
Many know Midi and Mega fuse, but those are rated 32 Vdc. Now, Littelfuse have released the High performance version of the Midi and Mega fuses.
Midi is rated 70V dc and the Mega is offer in 70Vdc and 120Vdc format.
 
Other interesting new fuses for the DIY stuff.
Many know Midi and Mega fuse, but those are rated 32 Vdc. Now, Littelfuse have released the High performance version of the Midi and Mega fuses.
Midi is rated 70V dc and the Mega is offer in 70Vdc and 120Vdc format.
Can you provide links?
 
I can't say for certain but it does give me pause that the MIDI one has interrupt rating of 2500 A @ 70 V DC whereas a class T would have 10kA
 
I can't say for certain but it does give me pause that the MIDI one has interrupt rating of 2500 A @ 70 V DC whereas a class T would have 10kA
Yes, the Midi is clearly not a fuse for a huge storage battery, but can be really useful for a small 48V system or for small EV (e-bike, quad, motorcycle, etc).
The fact that all the fuses in this thread have a cost of 4$ to 15$ is an important gain when compare to Class T fuse.
 
Great thread! Thank you for gathering all this info. Just wondering if there is something I am missing here. With such good performance in the AMH fuses, why would people spend money on the Class T fuses? Is it simply the difference in resistance (less loss) people are ready to pay for?
 
With such good performance in the AMH fuses, why would people spend money on the Class T fuses? Is it simply the difference in resistance (less loss) people are ready to pay for?
To me there is two reasons:
1-This is a relativly new product. Not every people know it exist.
2-The T class fuse blow at lower current, so a bit faster in a short circuit event. Fractions of second faster, so could be negligible.

Based on the spec, the loss at the fuse are not greater for the AMH.
Ok, it only 17W of lost at 350A. Is it right? 0.00014x350=0.049x350=17W? Or resistance can change drastically at high temperature?
If it's right, I don't understand how a 350A T class fuse can be rated at 40W of lost at 350A
 
Great news! I'm currently swapping the battery for lithium in my Subaru Elcat EV, and was looking for fuses. I have 30s1p battery (EVE LF280K). Max draw is below 200A and voltage will be max 103,5V. The AMH-350 seems good for that at a 10th of the price of a T-Class fuse. Again, thank you for gathering this info so well here. (btw, I actually got here by searching for "AMH fuses" in duckduckgo :D)
 
Reviving this old thread. Did any of you ended up using AMH fuses in your build? If so, can you please upload a picture?
I can't seem to find any bolt down posts or fuse holders for these : (
 
Damn thing is so small! I bought some studs to mount both ends and they were thicker than the fuse itself
 
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