Battery balance - Victron Energy

 The problem: the life of a battery bank, which is expensive, can be considerably reduced due to an imbalance in the charges.

A battery with a slightly higher internal leakage current on a 24 or 48 V bank composed of several batteries connected in series / parallel will cause the batteries connected in parallel to be undercharged, and the batteries connected in series to be overcharged. In addition, if new cells or batteries are connected in series, they must have the same initial state-of-charge. Small differences will dissipate during the absorption or equalization phase of the charge, but larger differences will cause damage due to either excessive gas evolution from batteries with a high initial charge state (caused by overcharging), or to the sulfation of batteries with a low initial state of charge (caused by undercharged batteries).

The solution: balancing battery charges

The Battery Balancer equalizes the state of charge of two 12 V batteries connected in series, or of several rows of batteries connected in series, these rows being themselves connected in parallel. If the charging voltage of a 24 V battery system rises above 27.3 V, the Battery Balancer will turn on and compare the voltage on the two batteries connected in series. The Battery Balancer will extract from the battery (or batteries connected in parallel), having the highest voltage, a current of up to 0.7 A. The resulting difference in charge current will guarantee that all batteries will converge to the same state of charge.

If necessary, several balancers can be installed in parallel. A 48 V battery bank can be balanced with three Battery Balancers.

LED indicators

• Green: active (battery voltage> 27.3 V)

• Orange: lowest active battery circuit (deviation> 0.1 V)

• Orange: highest active battery circuit (difference> 0.1 V)

• Red: alarm (deviation> 0.2 V) Will remain activated until the deviation decreases to less than 0.14 V, or until the system voltage drops to less than 26.6 V .

Alarm relay

Normally open. Closed if the red LED is on, and open if the red LED is off.

Alarm reset

Two terminals are available to connect a push button. By connecting the two terminals, the relay is reset. The reset condition remains active until the alarm condition has expired. Thereafter, the relay will close when an alarm is triggered again.

More information and control thanks to the center voltage monitoring function of the BMV702 battery controller.

The BMV-702 measures the median voltage of a row of cells or batteries. It displays the deviation from the ideal median voltage in volts or as a percentage. Separate deviation percentages can be set to trigger a visible / audible alarm, and to close a dry contact of a relay for remote alarm purposes. Please refer to the BMV-702 manual for more information on battery balancing.