Quattro 12/5000/200 Fuse Type and Quantity

DIY
1

I’m installing a Quattro 12/5000/200 with (4) NG 300Ah batteries (1200Ah total)
I’ve found the T-Class In for aggregating the batteries into a BMS 1000, then a Distributor 1000
[T-Class In]–>[T-Class In]–>[BMS 1000]–>[Distributor]
I’m using (2) 4/0 cables from the distributor to the Quattro.
However, when sending the power to the Quattro, what fuse type and size should be used? I see the docs state 800A fuses, however is that (1) 800A fuse, or two 400A fuses (1) for each 4/0 cable?

2

Reading more, I see suggestions its bad to split the cables into two fuses. However, I’m unable to find a good suggestion for an 800a fuse, and this diagram Victron Schematic shows two 350a mega fuses.
Yes, I know folks suggest 24v or 48v; however, the boat is 12v and it is difficult to convert all the systems. I wrote up the 12/24/48v discussion here: Hull Yeah Solar and Energy System Updates

3

I personally dont see an issue with using two fuses in parallel, if you also use two cables in parallel. But be aware that current distribution between those two cables is not guaranteed to be 50/50, i would even tend to say its guaranteed NOT to be 50/50. Even minute differences in length, crimping, whatever contact resistance, will result in unequal current flow.

So if you split an 800A fuse rating between two physical fuses, you may in theory need to consider using two 450A fuses, and also use cable gauges for that current of course. In practice i guess its going to be rare that you actually need the full 800A, since that would mean 9.6kW at 12V which the MP12/5000 is only capable of outputting for short periods. If you stay within rated AC output limits your DC side should be fine with 450A total.

Whenever you use parallel cabling, its good to measure current distribution under load, to make sure that theres not a single cable carrying most of the current. Id say up to 55/45 (or a 10% difference) is acceptable. If its more you should look into what is causing the difference, and try to correct it.

1 Like
4

Thanks, Chrigu for not getting on soapbox and providing a very practical answer. Much appreciated.