Victron Battery Balancer connections

One Battery Balancer equalizes the two 12 V batteries in a 24 V series bank. It begins operating above 27.3 V and stops below 26.6 V. Its balancing current, up to 0.7 A, is small compared with propulsion or inverter current; it cannot repair an undersized, damaged or mismatched battery. Three units are used for the four batteries of a 48 V arrangement. See operating description, PDF p. 1.

The negative lead goes to the bank negative, the positive lead to the bank positive, and midpoint to the series junction between batteries. Connect negative, positive, then midpoint, using at least 0.75 mm² cable. Do not connect midpoint to a chassis-grounded negative bus: it sits at the voltage of the lower battery. The catalog therefore exposes these as signal connections rather than a pass-through power bus.

For an installation requiring UL compliance, the manual specifies 10 A DC fuses in all three battery leads, close to the batteries. Other installation protection must still match the conductors and local requirements. The normally open alarm relay is rated 1 A at 60 V; its contacts need a separate supply to operate an indicator. Reset is a momentary external contact, not a power-input terminal. See connection order and specifications, PDF p. 2.

Measure each battery while the bank is charging and the balancer is active. A 200 mV difference activates the alarm; it clears below 140 mV. Persistent imbalance after sufficient charging warrants checking individual battery condition and connection resistance. A quiet alarm with the bank below the activation voltage does not establish that the batteries are balanced.