Battle Born 2S2P 24V Fusing and Victron

[NordicNerd]

Hello All,

I have noticed when looking at a few different diagrams at either Victron’s or other installers’ wiring diagrams that battery banks with 400 amp hours and less (12v and 24V) are not fused close to the batteries. Instead there is a downstream fuse located after the main disconnect switch. I assume that is because they are protected by the battery BMS.

Looking at fusing my own system I am considering using MRBF fuses on each 24 volt battery string then one main t-class fuse (or mega fuse in a Lynx Shunt or distributor).

Curious on people’s thoughts on this - I know there are a few approaches.

Also, i’m not sure if I understand why Victron for their Multiplus II 24/3000 recommends a 300 amp fuse. I would think it should be 175 amp or 200 amp or for a 2/0 wire I am using - or for the inverter 175 amp for the 2400 W continuous rating.

It would appear Victron may be implying that the fuse size is for the peak wattage of 5500 watts at 24 volts for a a 300 amp fuse.

My take is:

- 175 amp MRBF at each battery string to ensure battery cables protected (2/0 for each string).


- main fuse of 175 Amp to 24/3000 multiplus as max current in 2/0 cable is 175 amp

Anyone else have any thoughts on this - definitely appreciated.

Thanks!

 

[MisterSandals]

I assume that is because they are protected by the battery BMS.

BMSs fail, not to be relied on.

Looking at fusing my own system I am considering using MRBF fuses on each 24 volt battery string then one main t-class fuse (or mega fuse in a Lynx Shunt or distributor).

Not bad. What is AIC of your mega fuse? DC can arc across big gaps so class T fuses are kind.

Multiplus II 24/3000 recommends a 300 amp fuse.

I'll use 3000W for simplicity (laziness?)

3000W / 20V inverter cutoff / .85conversion efficiency = 176A

I would think it should be 175 amp or 200 amp or for a 2/0 wire I am using

How long is this wire? 2/0 good for 175A 15' one way. 200A fuse would protect that wire.

Anyone else have any thoughts on this - definitely appreciated.

I think your numbers in your post are very reasonable.

 

[NordicNerd]

Not bad. What is AIC of your mega fuse? DC can arc across big gaps so class T fuses are kind.

Looking for minimum of 10,000 AIC - I can find MRBF, mega and T-class all with that rating.

How long is this wire? 2/0 good for 175A 15' one way. 200A fuse would protect that wire

Longest run might be 6 feet.