Any input here would be appreciated. I am configuring a 24v system based on the M8 Lynx system and six 24V 200amp hr Smart Lithium batteries controlled by a Lynx M8 Smart BMS (500amp limit). The batteries are coming in through Lynx distributors (2) so I need to select six megafuses to fuse each battery as it comes in. The inverter has a sustained draw of 170amps/ peak of 300amps. The manual for the M8 BMS warns: “The total value of the fuses of all circuits should not be more than the current rating of the Lynx module with the lowest current rating” (500 amps in this case). If this is indeed the case then it seems like the six fuses could be no more than 500/6=83 amps which seems on the low side although under normal operation, even at peak, the inverter should be drawing no more that 300/6=50amps from each battery. The battery cables coming into the lynx system are 1 meter, 1/0 (53mm sq) which are bigger than needed so I don’t think I would fuse specifically to the cable specs-which could be as much as 350 amp fuses (x6), and if I understand the Victron warning about limiting the total sum of fuses in circuits to the BMS, this would be hugely above the 500amp limit. So… Am I thinking about this correctly, or am I misunderstanding the intent of the Victron BMS warning? What size megafuses should I be using this setting?
I would fuse 100A on each as I believe the BMS has a short term 600A limit.
With all those batteries, you may want to use the 1000A BMS, as they can provide 200A continuous each (assuming they are the VIctron Smart 25V 200Ah and not the Renogy Smart 200Ah).
Otherwise, yes, you should find a 75-85A fuse for each circuit, but you would seriously be hampering the capability of your excellent battery bank. Also, if you needed to isolate one or more battery from the system, the remaining batteries would be limtied from the small fuses.
Your best bet here is to use the correct BMS to match your system design, and then use 150A or 175A fuses.
An alternative design is seperating the batteries with 3 into one Lynx and one BMS and the other 3 in another Lynx and another 500A BMS>
FYSA, you can also use the Lynx Power IN and add fuses to it (if you don’t need the LEDs or fuse monitoring).
Thanks pwfarnell. That’s a good point.
Thanks. Yes my batteries are the Victron. Those are all good suggestions. I have considered the 1000 Amp BMS, but it wasn’t available when I purchased my first round of components so all my Lynx modules are the M8 flavor and I would need to upgrade everything to M10 if I got the 1000 BMS. I might get there anyway since my long-term plan is to upgrade to a 48V inverter and pair up the 24V batteries into 3 banks and fuse with T class fuses, either as part of T class Power Ins, if I can get them close enough to the batteries, or Blue Sea Holders/fuses if not.