Blue Sea Systems automatic charge relay. 12/24V, 120A.
Automatically manages the charging of two battery banks and isolates batteries during starting to protect sensitive electronics
• Designed for 12 or 24 volt systems.
• Hermetically sealed contacts/vaporproof.
• Waterproof rated IP67.
• Ignition protected—safe for installation aboard gasoline powered boats.
• Remote LED output indicates relay state away from ACR.
• Supports high-output alternators up to 120 Amperes
• Dual sensing.
Automatic Charging Relays Explained:
In a boat with two battery banks, it is useful to be able to charge both banks while underway. Charge management devices connect two battery banks when charging, and isolate them from each other when not charging. If one battery becomes depleted, there will be a charged bank available for emergency starting.
There are two main types of charge management devices used on boats:
Automatic Charging Relays use a relay combined with a circuit that senses when a charging source is being applied to either battery. When a charge is being applied, the ACR combines the batteries. When there is no charge present, the ACR isolates the batteries.
Battery Isolators are one-way electrical check valves that allow current to flow to, but not from, the battery. Their disadvantage is that the diodes used to achieve this cause a voltage drop that consumes charging energy, creates heat, and causes batteries to be undercharged. Although alternators with external voltage sensing can correct for undercharging, voltage drop and heat remain a problem.