Lynx Smart BMS sizing and fusing with Smart 330AH batteries

[Maix]

Hello Victron community,

I’m putting together a system for a motorhome and I have three (3) questions

1. First one is concerning the current rating of the Lynx BMS :
   I have a 12V Victron Smart battery 330AH and might be adding another one in parallel down the road. I’m planning to use a Multiplus 12/1600/70 as an inverter/charger.
   What value should I look for when deciding between a Lynx BMS 500 or 1000 ? Is it just the power draw of the inverter ? (And that would mean I must not exceed 6kw as stated in the doc of the BMS).
   Or should I also consider the max discharge value of the battery which is 400A (800A with two 330AH in parallel) ? What if I have a 12V AirCo pulling 1000W ? What if I bump up to a 12/3000 inverter ? This is not clear for me as you can see.

2. Second one is the fusing of these 330AH :
   I might be wrong but is the ICC of a single 330AH exceeding any mega fuse ICC rating ? What would you recommend in the single and parallel config ? The single can accommodate a ANL fuse as the fuse casing is external, but what about the parallel setup with the fuses in the Lynx Distributor ? Do I already need to go with the Class-T Power-In ?

3. And last one is the Battery Protect :
   What is the use case of the Battery Protect on the 12V loads line, That looks redundant to me looking at the BMS features, but I’m sure I’m missing something.

Here’s some diagrams to illustrate my setup :

With one battery :

With Two 330ah in parallel :

Thank you very much to anyone taking a look at this, I stay here to answer anything if I wasn’t clear.

Cheers !

[pwfarnell]

1. The decision on the BMS rating depends on your planned maximum power requirement. For example I have 12V 3000VA multiplus and maximum 12V loads of 100A so i am using the 500A BMS.
2. The mega fuse has too low ICC (AIC). Class T is suitable. There have been some recent posts using Adler EF3 fuses in a Lynx distributor. The fuse rating depends on the wiring rating, the max battery discharge current and the max power demand. For example I have 2 x 300Ah 12V Victron NG batteries in parallel with a 300A Class T fuse on each battery with 350A rated cable and the Lynx NG BMS is rated at 600A short term.

Post regarding Adler EF3 fuses

3. The battery protect on DC loads is optional. For the Victron equipment MPPT, Multiplus etc) there are 2 layers of protection, DVCC control and the contactor. If you fit a Battery protect from the ATD signal tjen you have 2 layers of protection, plus you can drop some loads before the contactor opens, hopefully keeping the BMS and GX device on line for a longer period. You could just rely on the contactor. I have a Smart Battery Protect.on my DC loads.k

[Maix]

Thank you very much for your answer, complete, precise and well worded ! This helps a lot to validate my design !