A battery master switch that can only be operated directly on the device is almost always located in the most inconvenient place in the system. The TSC master switch interface changes that – and also provides two protection functions that a mechanical switch cannot.
What the TSC does
The TSC is an interface that controls the external battery disconnect switch FBR 500. It is operated via the P-Bus, i.e., via the system monitor – or via an external control button that operates independently of the bus.
In addition to the pure switching function, it offers two adjustable protection functions: a deep discharge protection, which disconnects the bank if the voltage falls below a threshold, and an overvoltage shutdown. Both thresholds are set on the system monitor PSM 3 or PSL, not on the device.
The self-consumption is 2 mA – low enough not to matter during a long standby period. The interface operates at 12 and 24 V DC and measures 111 x 90 x 41 mm; an M12 T-cable is included.
The 260 Ampere Limit
The most important design consideration: The TSC alone carries a continuous current of 260 A. In combination with the FBR 500 battery disconnect switch, the load capacity increases to 500 A.
This leads to the decision rule. If the current through the master switch remains continuously below 260 A, the TSC operates independently. If high-current consumers are added – bow thruster, anchor winch, large inverters – the FBR 500 should be included.
The FBR 500 is not included in the scope of delivery and is ordered separately, in the 12 or 24 V version.
WarningThe decisive factor for the design is the current that can flow through the master switch – not the current that usually flows. A bow thruster rarely runs, but when it does, its full current passes through the same point.
Why an external control button is essential
Operating via the bus is convenient. However, it has a dependency: it only works as long as the monitor is operating and the bus is in order.
An external control button solves this. It works independently of the P-Bus and thus serves as an emergency override – operable even if the monitor fails or the bus cable is damaged. That is precisely why it is recommended and should not be considered optional.
The sensible location is the same place where you would have looked for the master switch: easily accessible, known, reachable without disassembly.
Setting deep discharge protection appropriately
The shutdown threshold is not a numerical value from the battery's datasheet, but a compromise. Set too high, it disconnects during normal operation. Set too low, it only intervenes when the bank has already been damaged.
Two considerations help. First: The voltage under load is lower than the open-circuit voltage – a threshold that seems sensible in idle mode will trigger prematurely under load. Second: For LiFePO4, the voltage barely drops over large parts of the discharge range and then sharply declines at the end. A voltage-based threshold will intervene late there; the actual protection comes from the battery's BMS, with the TSC serving as the second layer.
PIN protection and naming
Operation can be PIN-protected – useful wherever the control unit is accessible to several people and accidental disconnection would have consequences.
Each master switch can also be assigned its own name. In a system with multiple switches, this is not a gimmick: "Consumer master switch" and "Bow thruster master switch" are distinguishable, while "Switch 1" and "Switch 2" are not in an emergency.
Check after installation
- Switching via the monitor works in both directions.
- Switching via the external button also works – even when the monitor is switched off.
- The deep discharge threshold is set and is below the voltage that occurs under load in normal operation.
- Naming is clear and matches what the switch actually disconnects.
- Everyone on board knows where the emergency switch is located.
Typical Errors
- TSC without FBR 500 for high-current consumers. Above 260 A, the disconnect switch is required.
- FBR 500 mistakenly believed to be included. It is not included in the scope of delivery; an M12 T-cable is in the box.
- No external control button. Without it, the operation of the master switch depends on the bus.
- Deep discharge threshold set according to open-circuit voltage. Triggers prematurely under load.
- Switch not named. With multiple switches, this is a prerequisite for selecting the correct one.
