Blue Sea Systems m-ACR Automatic Charging Relay 12V Atd. 65A configurable multi-mode battery protector

Blue Sea Systems m-ACR 65A is a configurable automatic charging relay that lets you select timer disconnect, low-voltage disconnect, automatic charging relay, or solenoid behaviors to protect and manage 12V battery systems.

Designed for marine, RV, and off-grid 12V installations, the m-ACR 65A provides flexible battery management in a single compact unit. Instead of buying separate devices for timed loads, low-voltage protection, or charge isolation, this relay can be set up to perform the role you need — from joining batteries during charging to disconnecting nonessential loads when voltage falls. Its single-side sensing and simple 12V control options make it especially useful with starter and larger auxiliary batteries such as AGMs.

How does the m-ACR protect batteries during discharge?

When configured as a low-voltage disconnect, the m-ACR monitors battery voltage and will open the relay to isolate loads before the battery reaches a harmful level. This helps preserve reserve capacity for essential systems and prevents deep discharge that shortens battery life.

• Adjustable disconnect thresholds to suit battery chemistry and system needs
• Automatic reconnection once the voltage recovers or when charging is detected
• Can work alongside timer disconnect mode for staged protection

In what way can it act as a timer disconnect for nonessential loads?

Configured as a timer disconnect, the m-ACR will close the relay when a 12V trigger appears and begin a countdown when the trigger is removed. After a preset duration it will open again, letting you run accessories for a controlled interval without draining the battery indefinitely.

• Timer ranges from 15 minutes up to 4 hours to fit common use cases
• Ideal for courtesy lights, entertainment systems, or auxiliary pumps
• Prevents accidental overnight drain by automatically cutting power

What does the automatic charging relay (ACR) function do?

In ACR mode the device parallels two battery banks when a charging source raises the starter battery voltage, then isolates them when the system begins to discharge. This lets alternators or chargers replenish both batteries while keeping them separated during engine-off periods for reliable starting and longer auxiliary service.

• Single-side sensing monitors the start battery voltage for reliable connect/disconnect
• Suitable for charging AGMs and larger auxiliary batteries without manual switching
• Prevents one battery from discharging the other during heavy loads

Can it be used like a simple solenoid or remote switch?

Yes — in solenoid mode a 12V control signal will directly open or close the relay without any timing delay. This gives you straightforward remote on/off control for accessories or battery connections where immediate switching is desired.

• Fast, delay-free switching on a 12V command
• Useful for integration with existing control panels or alarms
• Compact footprint for tight installation spaces

Who is this for? The Blue Sea Systems m-ACR 65A is aimed at boaters, RV owners, and small off-grid system builders who want one versatile device to handle charging isolation, timed accessory control, low-voltage protection, or a simple remote-controlled solenoid. If you need reliable 12V battery management without adding multiple dedicated modules — especially when using starter batteries and larger auxiliary AGMs — the m-ACR delivers configurable options in a single, serviceable package.