SolidSwitch 104

The SolidSwitch switches DC loads of up to 70 V/4 A

It can be controlled by a digital signal with low power (>3.3V >30uA).

The DC load can be resistive, capacitive or inductive (e.g. the coil of a high-power contactor).

The SolidSwitch is not protected against reverse polarity and is not short-circuit-proof.


It is used for load and charge disconnection in lithium BMS. It is also ideal for switching off your light engine (interrupting the excitation voltage)

It has three typical applications:

1. Control of an external alternator regulator / alternator, e.g. a Balmar or Mastervolt Alpha pro in a Victron lithium system.

2. Switching a direct current load, e.g. a light. A low power controller, whose maximum current consumption is only 100 μA, can then control a load of up to 4 amps.

3. Increase the number of chargers that can be connected to the ATC (Allow-to-Charge) output of a Victron BMS.

What makes the SolidSwitch 104 so unique?

The feature that makes it such a useful switch is its low power consumption. The SolidSwitch consumes 0.04 Ah per month, whereas a small relay can easily consume 10 Ah per month or typically even 22 Ah (*).
This reduction by a factor of 250 is crucial when used in a lithium system to connect and control the alternator regulator:

The control circuit always consumes its standby power. The same applies if it is used to increase the number of chargers that can be connected to a BMS-ATC contact. By using a SolidSwitch instead of an ordinary relay, the parasitic load is reduced to the order of magnitude of the self-discharge of the battery bank .
Note that the ATC output of the BMS is still activated even when the batteries are fully charged. And therefore control circuits such as a relay or in this case the SolidSwitch are activated and consume power. Even if the charger or generator is not charging.

In this example, this means that when using a relay, the small relay draws 10 Ah per month from the battery bank, even when the engine is not running.
The SolidSwitch, on the other hand, draws only 0.04 Ah, which is most likely far below the self-discharge of the batteries and therefore negligible.

(*)
For example, if a 12 V 1 A relay with a 400 ohm coil is used, the current consumption is 30 mA or 21.6 Ah per month. Compatible load types The DC load can be resistive, capacitive or inductive (e.g. the coil of a high-power contactor).