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Blue Sea Fuse Block: 32VDC really?

scott harris

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Jan 1, 2020
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I bought a Blue Sea fuse block for my 16s 280AH battery build. It is the one with 12 terminals, 30 amps per terminal 100 amps per block. Its purpose is to provide protection for low power items like the alarm horn, bms, pack voltage sensor/relay etc. But i see on the specs on the back of the package that it is rated for only 32 VDC. Really? Can pushing 56 VDC (pack max voltage) at 1 to 2 amps per connection really cause a problem?
 
IMHO, there is no danger of arcing on the fuse holder itself unless something else comes into close contact. The insulating material is more than enough to handle 60V.

HOWEVER.... ATC fuses are only rated to 32V. The question then becomes: Can you use a 32V rated ATC fuse in a 48V application.

The first answer is: NO. Never use a component beyond it's rated voltage.

The following is for informational purposes only. I am making no recommendations or claims:
Having said that, people have been know to use ATC fuses in 48V circuits.

Here is a thread from a different forum that discusses it.


As the voltage and current go up, you run a larger and larger chance of the fuse creating a small explosion and/or creating an arc that does not extinguish.


So, can you use ATC fuses on 48V? Maybe, but perhaps more importantly, Maybe not.
 
Great response. And the video gives me an idea. I think I will blow a few 3 amp fuses, some at 32 volts and some at 60 volts to see if there is any difference.
 
I see 48V inverter built-in fuse is 32V 10A, so I think you can use ATC fuses on 48V
 
Great response. And the video gives me an idea. I think I will blow a few 3 amp fuses, some at 32 volts and some at 60 volts to see if there is any difference.
When you test, keep in mind the 3 critical aspects of selecting a fuse:

1) Rated Voltage
2) Rated current it will blow at.
3) The amount of current it must interrupt.

The 3rd one is often overlooked. When a short occurs, the current ramps up almost instantly. With the extremely low internal resistance of the LiFePO4 cells we use, that means that the current can be huge by the time the fuse actually blows.

I am willing to bet that if you did experiments on a 10A fuse with a 60V 30A power supply, the results would be less 'interesting' than with a 60V LiFePO battery.
 
I contacted Blue Sea systems with the same question, and they confirmed for me that the voltage rating of 32V listed for the fuse block is just a limitation of fuse, not the actual block. My solution was to go to Digikey and find ATO/ATC form factor fuses rated to 58V -- they exist! Optifuse APR58 series:

First post here; great discussion on this forum.
I used this thread's fuse info when building my DIY powerwall, and have more review of 48V system fuse selection here:

Cheers,
Mike
 
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