Hey folks,
For the past few days i can't wrap my head around on how to select the correct BMS size because of the inverter. The right fuse size is also a huge question for me.
Explanation:
In my camper van setup (12V) I will be using an Victron Multiplus 12/800 inverter. This means the unit can deliver 800W for 30mins (or 700W constant at 25°C ).
However the inverter also has a peak-power specified of twice the nominal power = 1600W (2 x 800W) for 0.5 sec.
The inverter goes into overload and shuts of after these 0.5 sec.
My point:
The system is designed the following way: Batterie -> main fuse -> distribution box --> all devices (charger, inverter, 12V devices)
So if I make quick calculation for worst case (max. inverter load + max. load of all 12V devices (~50A) ) this results in either:
Nominal Power:
800W/12V + 50A = ~120 A (continous)
Peak Power:
1600W/12V + 50A = ~190A (for 0.5 sec)
Sure the peak power is potentially never pulled, because it would mean I would have to connect an electrical heater with 2000W without thinking. But as far as I know the BMS should be your "last safe" which protects the battery itself while the fuses "before" it pop. That is why I personally believe a 200A BMS is the right choice.
Case 1:
I take a 200A BMS and put a 150A main fuse after my BMS the above calculated peak voltage (190A) would trigger the fuse and shut down the whole system.
Case 2:
I put a 200A fuse as main fuse and protect the inverter separately with 150A. All would be fine but in case of a short it would be a game of "who triggers first" between the BMS and the main fuse.
My Questions:
1) Use a 150A or a 200A BMS?
2) Which size should my main fuse be?
3) Should I put a extra 150A fuse in front of the inverter although it has a internal 150A fuse?
Thank you in advance and for your time.
Best wishes from Austria,
Watzi
For the past few days i can't wrap my head around on how to select the correct BMS size because of the inverter. The right fuse size is also a huge question for me.
Explanation:
In my camper van setup (12V) I will be using an Victron Multiplus 12/800 inverter. This means the unit can deliver 800W for 30mins (or 700W constant at 25°C ).
However the inverter also has a peak-power specified of twice the nominal power = 1600W (2 x 800W) for 0.5 sec.
The inverter goes into overload and shuts of after these 0.5 sec.
My point:
The system is designed the following way: Batterie -> main fuse -> distribution box --> all devices (charger, inverter, 12V devices)
So if I make quick calculation for worst case (max. inverter load + max. load of all 12V devices (~50A) ) this results in either:
Nominal Power:
800W/12V + 50A = ~120 A (continous)
Peak Power:
1600W/12V + 50A = ~190A (for 0.5 sec)
Sure the peak power is potentially never pulled, because it would mean I would have to connect an electrical heater with 2000W without thinking. But as far as I know the BMS should be your "last safe" which protects the battery itself while the fuses "before" it pop. That is why I personally believe a 200A BMS is the right choice.
Case 1:
I take a 200A BMS and put a 150A main fuse after my BMS the above calculated peak voltage (190A) would trigger the fuse and shut down the whole system.
Case 2:
I put a 200A fuse as main fuse and protect the inverter separately with 150A. All would be fine but in case of a short it would be a game of "who triggers first" between the BMS and the main fuse.
My Questions:
1) Use a 150A or a 200A BMS?
2) Which size should my main fuse be?
3) Should I put a extra 150A fuse in front of the inverter although it has a internal 150A fuse?
Thank you in advance and for your time.
Best wishes from Austria,
Watzi