I am designing a 24V campervan electrical system using the following Victron components:
2 × Lithium NG 25.6V 300Ah batteries
Lynx Class-T Power In M10
Lynx Smart BMS NG 500A M10
MultiPlus-II 24/3000
Lynx Distributor
Orion XS 1400
SmartSolar MPPTs
I would like to confirm the recommended Class-T fuse size for each battery connection to the Lynx Class-T Power In.
I have seen a Victron system example using 350A Class-T fuses with two 25.6V 300Ah NG batteries, but I have not found a document explicitly stating the required or recommended fuse value for this battery model.
Could you please advise which Class-T fuse rating Victron recommends per battery for this configuration?
Specifically, I would like to know whether 300A, 350A, or 400A Class-T fuses are recommended and whether there are any considerations regarding warranty compliance or system certification when selecting the fuse size.
I would put a individual T-Class fuse for both batteries.
T-Class fuses are great for being capable of stopping a Lithium battery short circuit arc. Mega fuses are not.
Also for the amperage, main selection criteria is always:
1. Wire size to make sure it does not heat up and start a fire and/or melt the insulation
2. Being capable of feeding your max load even if one of the batteries goes offline(double the amperage for the remaining one). So make sure the gauge is large enough for that possible situation.
For the manufacturer. I have had great experiences with Blue Sea Systems (250A and 400A with personal experience).
Victron SmartLithium can not go offline individually. The batteries have no switching element in the main current path, they only contain a balancer board (and a shunt with the NG-series).
The switching is done in the lynx BMS. So you either have both batteries connected to the system, or none.
The SuperPacks however work like most of the LFP packs available, with an integrated BMS that can switch the main current path.
I wouldn’t trust that in a 2 battery unit system. There is always the situating of an internal malfunction of a single battery. Or if one changes the batteries(to a CANbus solution with 2 larger units) and takes off the Lynx BMS without thinking about the whole link. “Life finds a way to crush your dreams”. With short wiring there is no reason to skimp on the wire gauge to make it extra safe(and leave room for future improvements).
But, just my 2cents, people can do what they like. As an engineer that knows my tendency to always want more in the future, I have learned this lesson all too well.