Temperature, battery cell chemical composition, and individual battery self-discharge rates can cause battery systems in series to become unbalanced. This imbalance will result in the batteries incorrect charging (under or overcharging) ultimately causing sulphation and premature plate corrosion. As the battery system ages, this voltage discrepancy will increase, resulting in early battery system failure.
Enter the Valen Battery Equaliser range:

The Valen battery equaliser, equalises or balances out these voltage discrepancies as soon as a 2mV battery voltage difference has been detected. By adding a Valen Battery Equaliser to the battery system, the performance will be enhanced, and the battery life drastically improved. Valen Equalisers come in a variety of sizes, allowing them to be retrofitted into a variety of applications. Multiple Valen Battery Equalisers may be used on one system for the complete system to be covered.