Battery isolator relay wiring diagram is an important topic for vehicle owners, especially those who use multiple batteries to power their devices. A battery isolator relay is a device that allows two or more batteries to be charged from the same charging source but prevents the batteries from discharging each other. In this article, we will discuss the basics of battery isolator relay wiring diagrams, common misconceptions about them, and how to install them in your vehicle.
What is a Battery Isolator Relay?
A battery isolator relay is a relay that allows the charging of multiple batteries from the same source without allowing the batteries to discharge each other. It is commonly used in vehicles that require an additional battery or batteries to power auxiliary devices such as lights, winches, or amplifiers. The battery isolator relay ensures that the primary battery is always charged first and that the secondary battery or batteries are charged secondarily.
There are two types of battery isolator relays: diode-based and solenoid-based. Diode-based battery isolator relays are cheaper but less efficient than solenoid-based isolators. Solenoid-based isolators are more expensive, but they are more efficient and have higher current ratings.
How to Wire a Battery Isolator Relay?
The wiring of a battery isolator relay depends on the type of isolator used. Diode-based battery isolators require three wires: a ground wire, a positive wire from the primary battery, and a positive wire from the secondary battery. Solenoid-based battery isolators, on the other hand, require four wires: a ground wire, a positive wire from the primary battery, a positive wire from the secondary battery, and a wire to activate the solenoid.
The wiring diagram for a diode-based battery isolator relay is as follows:
| Wire Color | Function |
|---|---|
| Black | Ground |
| Red | Positive from primary battery |
| Yellow | Positive from secondary battery |
The wiring diagram for a solenoid-based battery isolator relay is as follows:
| Wire Color | Function |
|---|---|
| Black | Ground |
| Red | Positive from primary battery |
| Yellow | Positive from secondary battery |
| Blue | Solenoid activation wire |
Diode-based Battery Isolator Relay Wiring Diagram
The wiring diagram for a diode-based battery isolator relay is straightforward. The ground wire should be connected to a ground point in the vehicle, such as the chassis or negative battery terminal. The positive wire from the primary battery should be connected to the input terminal of the isolator relay. The positive wire from the secondary battery should be connected to the output terminal of the isolator relay.
It is important to note that the diodes in a diode-based battery isolator relay introduce a voltage drop of around 0.6 volts. This means that the secondary battery will never be fully charged unless the primary battery is fully charged first.
Solenoid-based Battery Isolator Relay Wiring Diagram
The wiring diagram for a solenoid-based battery isolator relay is slightly more complicated than a diode-based isolator. The ground wire should be connected to a ground point in the vehicle, such as the chassis or negative battery terminal. The positive wire from the primary battery should be connected to the input terminal of the isolator relay. The positive wire from the secondary battery should be connected to the output terminal of the isolator relay. Finally, the wire to activate the solenoid should be connected to a switch or other source of power.
Common Misconceptions about Battery Isolator Relay Wiring Diagrams
There are a few common misconceptions about battery isolator relay wiring diagrams that are worth addressing:
1. Battery Isolator Relays are Only for Boats and RVs
While battery isolator relays are commonly used in boats and RVs, they can be used in any vehicle that requires a secondary battery to power auxiliary devices.
2. Battery Isolator Relays are Complicated to Install
While the wiring diagram for a solenoid-based battery isolator relay is slightly more complicated than a diode-based isolator, installation is fairly straightforward and can be completed with basic tools.
3. Battery Isolator Relays are Not Necessary
While it is possible to connect multiple batteries to a vehicle without a battery isolator relay, doing so can lead to an unbalanced charge between the batteries, which can shorten their lifespan.
FAQs
1. Can I use a diode-based battery isolator relay with a high-output alternator?
Diode-based battery isolator relays are not recommended for use with high-output alternators because they introduce a voltage drop of around 0.6 volts. This can cause the alternator to work harder than necessary to charge the batteries, which can shorten its lifespan.
2. Can I wire multiple battery isolator relays together?
Yes, it is possible to wire multiple battery isolator relays together to charge more than two batteries. However, it is important to ensure that the relays are properly sized for the application and that the wiring is done correctly to prevent damage to the batteries or the vehicle.
3. Can I use a battery isolator relay with AGM batteries?
Yes, battery isolator relays can be used with AGM batteries as long as the wiring is done correctly and the relays are properly sized for the application.
4. Can I use a battery isolator relay with a solar panel?
Yes, battery isolator relays can be used with solar panels as long as the wiring is done correctly and the relays are properly sized for the application.
5. Can I use a battery isolator relay to charge two different types of batteries?
It is not recommended to use a battery isolator relay to charge two different types of batteries because their charging requirements may be different, which can lead to an unbalanced charge between the batteries and shorten their lifespan.
Conclusion
Battery isolator relay wiring diagrams are an important topic for vehicle owners who use multiple batteries to power their devices. By understanding the basics of how these relays work and how to install them in your vehicle, you can ensure that your batteries are charged correctly and that their lifespan is maximized. If you have any questions about battery isolator relay wiring diagrams or their installation, consult a professional mechanic or electrician.
