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Fuse recommendation for 48V Victron Inverter

Robkh

Robkh

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Jun 8, 2022
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Phoenix, AZ
Converting 12V system to 48V - 15,360Wh 300Ah battery equivalent wired to 1,820W Solar connected to a Victron Multiplus II 120V 48/3000/35-50 and a Victron SmartSolar charge controller MPPT 150/70 Tr.
Victron Multiplus II manual recommends 125A Mega fuse on battery line to inverter but many on the forum recommend T class fuse for better protection - probably 200A.
What say you learned souls?

Also what size and type of fuse or circuit breaker would you recommend from 300Ah 48V battery to the Victron SmartSolar charge controller MPPT 150/70 Tr?
 
Robkh said:
Converting 12V system to 48V - 15,360Wh 300Ah battery equivalent wired to 1,820W Solar connected to a Victron Multiplus II 120V 48/3000/35-50 and a Victron SmartSolar charge controller MPPT 150/70 Tr.
Victron Multiplus II manual recommends 125A Mega fuse on battery line to inverter
Click to expand...

This is likely consistent with their recommended conductor size.

Robkh said:
but many on the forum recommend T class fuse for better protection - probably 200A.
Click to expand...

You select fuse size based on conductor ampacity.

Class T has a higher AIC rating to ensure the fuse will work in extremely high currents and is often warranted when just considering the battery's potential short circuit current. When one factors in the total system resistance, the need for high AIC rated fuses diminishes and mega may work.

Robkh said:
What say you learned souls?

Also what size and type of fuse or circuit breaker would you recommend from 300Ah 48V battery to the Victron SmartSolar charge controller MPPT 150/70 Tr?
Click to expand...

1.25X conductor ampacity.
 
I have 1/0 battery cables. What is your recommended T class fuse size?
What wire gauge would you recommend from my 48V battery to the MPPT and what size fuse do you recommend for that MPPT wire?
Thanks.
 
Robkh said:
I have 1/0 battery cables. What is your recommended T class fuse size?
Click to expand...

1.25X the rating of that specific wire.

Robkh said:
What wire gauge would you recommend from my 48V battery to the MPPT and what size fuse do you recommend for that MPPT wire?
Thanks.
Click to expand...

Assuming you may use the maximum output of the MPPT at 70, wire rated for 70A fused for 1.25X the wire rating.
 
Robkh said:
Victron Multiplus II manual recommends 125A Mega fuse on battery line to inverter
Click to expand...
Just make sure that the megafuse you choose is rated for 60V+. Mine are specified for 70V DC, but many mega fuses are only good for up to 32V.

Another alternative choice would be an NH fuse.
 
sunshine_eggo said:
1.25X the rating of that specific wire.
Click to expand...
Interested why you say that? I always make sure my wire will handle 25% more current that the fuse can - as I prefer the fuse to melt before the wire does.
 
1/0 gauge ampacity is 170A X 1.25 = 212A fuse - nearest is 200A T class fuse battery line.
MPPT line 70A X 1.25 = 87.5A fuse - I have used ANL fuses before - can I continue to do so using one with a close match to 87.5?
 
SeaGal said:
Just make sure that the megafuse you choose is rated for 60V+. Mine are specified for 70V DC, but many mega fuses are only good for up to 32V.

Another alternative choice would be an NH fuse.
Click to expand...
Yes I had a Lynx distributor but I wasn’t able to find the Victron MPPT manual’s recommended 80-100A Megafuse in 58V size as Victron doesn’t make 58V mega fuses that small.
I ditched the Lynx and will use an 80-100A 48V ANL fuse as I am unfamiliar with NH fuses.
 
Robkh said:
Yes I had a Lynx distributor but I wasn’t able to find the Victron MPPT manual’s recommended 80-100A Megafuse in 58V size as Victron doesn’t make 58V mega fuses that small.
I ditched the Lynx and will use an 80-100A 48V ANL fuse as I am unfamiliar with NH fuses.
Click to expand...
Victron doesn't but littelfuse does:

www.currentconnected.com

LittelFuse MEGA Fuse - 60A to 300A for 12V/24V/48V Systems | Current Connected

Ensure uninterrupted performance with the LittelFuse MEGA Fuse. Safeguard your 12/24V systems from surges and enjoy peace of mind!
www.currentconnected.com www.currentconnected.com
 
I must point out that most of those littelfuse MEGA 58V rated fuses (transparent cases) are only rated for 1kA AIC (according to Mouser).

The 70v rated ones (black cases) are 2.5 kA AIC, and are superior.
The ones from Current Connected are the 70V ones.

This is why a good Class T with 20 kA AIC at the battery bank is critical to prevent the “moment of doom”.
 
Last edited:
ricardocello said:
I must point out that most of those littelfuse MEGA 58V rated fuses (transparent cases) are only rated for 1kA AIC.

The 70v rated ones (black cases) are 2.5 kA AIC, and are superior.
The ones from Current Connected are the 70V ones.

This is why a good Class T with 20 kA AIC at the battery bank is critical to prevent the “moment of doom”.
Click to expand...
Good info. Struggling to pony up $30 each for the 70V rated fuses when I can get an entire 250A 125V midnite DC breaker with 50,000 AIC for $46. But those breakers aren't going to fit in a lynx distributor so first world problems there
 
Brucey said:
Struggling to pony up $30 each for the 70V rated fuses
Click to expand...
Sounds a lot of money for a mega fuse. What about NH class fuse instead? - typically under $10 in UK - but maybe less commonly available in the USA :unsure:
 
SeaGal said:
Sounds a lot of money for a mega fuse. What about NH class fuse instead? - typically under $10 in UK - but maybe less commonly available in the USA :unsure:
Click to expand...
I guess they have the market by the short and curlies. Needs to fit in a lynx distributor so pretty much locked in on mega form factor.

Battery to lynx power in is protected by DC breaker so these are just the loads (sccs, inverter) that need fusing in the distributor.
 
Last edited:
ricardocello said:
@Brucey Be careful before you go buying those ! There are M6 and M8 variants, and zero-hole, one-hole, and two-hole variants,read the data sheet, don’t trust the picture! Check the part number.
View attachment 208924
Click to expand...
Thanks, I ended up getting two 125A Victrons for now which will hold me over until I need more smaller ones and then I'll stock up on these.
 
SeaGal said:
What about NH class fuse instead? - typically under $10 in UK
Click to expand...
Hard to find here inexpensively. I just read the Eaton-Bussmann catalog about NH fuses for DC applications, and am now confused.
IMG_6634.jpeg

Half the rating meaning Amps or Volts? they are not clear. Also, I have no control over the fault rise time.
Also, there are many sublclasses of NH which I don’t understand.


Maybe other vendors in UK/Europe/AUS are better.
 
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