Auto Charging Relay
Part No: 9800-7101-00
The automatic charging relay (ACR) automatically manages battery charging to ensure maximum efficiency and protect your batteries.
Key Features & Benefits:
Automatic battery management – connects batteries during charging and isolates them when voltage drops
Start Isolation (SI) – protects sensitive electronics during engine cranking by temporarily disconnecting house loads (indicated by a slow-flashing yellow LED)
High-output support – compatible with alternators up to 120 A
Dual-color LEDs – provide real-time battery status: Fault, Charging, Discharging, Combine, SI, and Override modes
Under Voltage Lockout – prevents the relay from closing when battery voltage is too low (9.5 V for 12 V systems, 19 V for 24 V systems)
Durable design – IP67 waterproof, ignition protected, safe for marine and RV applications
Applications:
Boats – dual battery systems (starter + house)
Sailboats – navigation and lighting batteries
Fishing boats – trolling motor and accessory battery protection
Specifications/Additional Info
Continuous Rating: 120 Amps
Intermittent Rating: 140 Amps
Max Voltage: 48VDC
Cable Size: 4/0 AWG
Spec Sheet
Battery Switches Brochure
Related Options
What Is an Automatic Charging Relay?
An ACR is a voltage-sensing smart switch that manages multiple batteries on your boat. It automatically links batteries when charging voltage is present and separates them when it drops.
Benefits:
Protects your starter battery from being drained
Improves charging efficiency compared to diode isolators (~0.6 V loss)
Eliminates the need for manual switching
Works seamlessly with alternators, chargers, and solar panels
ACR vs. Battery Isolator
Automatic Charging Relay (ACR):
Voltage-sensitive operation
Low internal resistance → minimal power loss
Automatic operation with modern charging sources
Battery Isolator:
Uses diodes to separate batteries
Higher voltage drop → reduced charging efficiency
Often requires high-output alternators
Verdict: ACRs are typically the preferred solution for modern marine dual-battery systems.
Frequently Asked Questions (FAQ)
Do I need an ACR on my boat?
Yes. An ACR keeps your starter battery safe and your house battery fully charged.
Can I install it myself?
Many models are DIY-friendly, but professional installation is recommended for complex systems.
Difference between ACR and VSR?
They are the same device; VSR is another term for an automatic charging relay.
Will it work with solar panels?
Yes. The ACR will connect batteries when the solar controller raises voltage.
- What Is an Automatic Charging Relay?
An ACR is a voltage-sensing smart switch that manages multiple batteries on your boat. It automatically links batteries when charging voltage is present and separates them when it drops.
Benefits:
Protects your starter battery from being drained
Improves charging efficiency compared to diode isolators (~0.6 V loss)
Eliminates the need for manual switching
Works seamlessly with alternators, chargers, and solar panels
- ACR vs. Battery Isolator
Automatic Charging Relay (ACR):
Voltage-sensitive operation
Low internal resistance → minimal power loss
Automatic operation with modern charging sources
Battery Isolator:
Uses diodes to separate batteries
Higher voltage drop → reduced charging efficiency
Often requires high-output alternators
Verdict: ACRs are typically the preferred solution for modern marine dual-battery systems.
- Frequently Asked Questions (FAQ)
Do I need an ACR on my boat?
Yes. An ACR keeps your starter battery safe and your house battery fully charged.
Can I install it myself?
Many models are DIY-friendly, but professional installation is recommended for complex systems.
Difference between ACR and VSR?
They are the same device; VSR is another term for an automatic charging relay.
Will it work with solar panels?
Yes. The ACR will connect batteries when the solar controller raises voltage.
Have More Questions?
Have a question? Fill out the form or reach us directly by phone or email using the contact details below.
1-855-258-3700
sales@bluewatergadgets.com
13620 49th St N Unit 101, Clearwater, FL 33762