Victron Battery Balancer

What is the function of the Battery Balancer and who is it for?
As its name suggests, the Battery Balancer is used to equalise the state of charge of batteries.
It is installed between two series connected 12 V batteries or parallel strings of series connected 12 V batteries with or without an integrated BMS. It is ideally suited for Lead-acid batteries. 
If your energy storage system uses such a battery configuration, a Battery Balancer is a good investment, that will help ensure the batteries last for as long as possible.

Features
The device is equipped LED status indicators on the front panel to indicate the current status.
It also features a connections for a (normally open) relay that can be used for an external alarm, as well as connections for an alarm reset switch.

How does the Battery Balancer work?
When the charge voltage reaches 27.3 V the Battery Balancer will engage and start comparing the voltage between the “upper” and “lower” battery. To equalise the state of charge the Battery Balancer will draw a current of up to 0.7 A from the battery (or parallel connected batteries) with the highest voltage. The resulting charge current differential is sufficient to ensure all batteries will converge on the same state of charge.
Multiple Battery Balancer devices can be used in parallel, for example three units can balance a 48 V battery bank comprised of 12 V batteries.

Is a Battery Balancer necessary?
To answer the question it is important to understand the problem that the Battery Balancer is designed to solve.
Different batteries will have a slightly different internal leakage current, when one battery has a higher leakage current, this will cause an imbalance that leads to that battery being undercharged, while the other battery is overcharged.
Lead-acid batteries with a lower initial state of charge will suffer from sulfation - a build up of lead-sulfate crystals, which is not always reversible, and is the most common cause of battery failure.
On the other hand batteries with a higher initial state of charge will suffer from damage caused by excessive gassing, caused by overcharging.
A Batery Balancer pays for itself by prolonging the useful life of batteries, both saving money for the user and reducing harmful waste.

Installation considerations
The Battery Balancer(s) should be installed close to the batteries, but not directly above them as corrosive gasses venting from the batteries can damage the device.
When engaged the device applies a resistive load, which produces heat, therefore mind the heat sink at the back and ensure proper ventilation. 

For more information, please refer to the technical documentation and manuals provided by the manufacturer, which can be found on this webpage.