Hi,
I am working on a system that uses two batteries and switches between them.
The small battery is 48DC 50AHr LiFePO4 .
The large battery is 48DC 100AHr LiFePO4 .
There are 3 work modes:
A: small battery is active. Current is up to 30 A .
B: large battery is active. Current is up to 60 A.
C: Idle mode. Current is 10 A.
Switching between batteries will be done only in Idle mode.
In my initial design there are relays to connect or disconnect the relevant battery.
The workflow is:
1.Press on the ON button. U1 will be active.
2.controller activates U2.
3.battery 1 is supplying current at up to 30 A .
4.Working at Idle mode.
5.controller activates U4. Both batteries are connected for a very short time.
6.Controller disconnects U2.
7.Battery 2 is supplying current up to 60 A .
8.Controller closes K1, activates U3 – charger.
9.charger will supply 5 A. that way battery 1 is trickle charged.
With this design I am worried that when both batteries are connected there might be a very high current between them, that may trip the BMS.
So, I was thinking about adding a big capacitor at V_OUT .
And switching by disconnecting both batteries and then activating one of them.
But because I will need a big capacitor, it may also cause the BMS to trip at power ON.
I am working on a system that uses two batteries and switches between them.
The small battery is 48DC 50AHr LiFePO4 .
The large battery is 48DC 100AHr LiFePO4 .
There are 3 work modes:
A: small battery is active. Current is up to 30 A .
B: large battery is active. Current is up to 60 A.
C: Idle mode. Current is 10 A.
Switching between batteries will be done only in Idle mode.
In my initial design there are relays to connect or disconnect the relevant battery.
The workflow is:
1.Press on the ON button. U1 will be active.
2.controller activates U2.
3.battery 1 is supplying current at up to 30 A .
4.Working at Idle mode.
5.controller activates U4. Both batteries are connected for a very short time.
6.Controller disconnects U2.
7.Battery 2 is supplying current up to 60 A .
8.Controller closes K1, activates U3 – charger.
9.charger will supply 5 A. that way battery 1 is trickle charged.
With this design I am worried that when both batteries are connected there might be a very high current between them, that may trip the BMS.
So, I was thinking about adding a big capacitor at V_OUT .
And switching by disconnecting both batteries and then activating one of them.
But because I will need a big capacitor, it may also cause the BMS to trip at power ON.