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Battery Isolators:
Many people listen to their stereo without the engine running. This often leads to dead batteries and a vehicle that won't start. A battery isolator will let you completely discharge one battery without discharging the starting battery.
Different Types of Isolators:
There are 2 main types of battery isolators. The diode based type and the relay (solenoid) type. W're only going to cover the Diode based type.
Diode Based Isolator:
This type of isolator is basically two very high current diodes in a heat sink. The diode based isolator has the advantage of long life and trouble free operation but many of the diode based isolators cause a .4 to .6 volt loss which means that the batteries will not charge to as high a voltage as when they are connected directly to the alternator. The diagram below shows the connection for the diode based isolator. Some diode type isolators have a fourth terminal which controls the current flow through the device.
Here is a typical Diode Based Isolator with fuse, and Amplifier connection:
The existing B+ terminal to your battery, goes to the center position of the Isolator. Then your two batteries are connected to the left and right sides.
DUAL BATTERIES WITHOUT AN ISOLATOR
Some people have good results when they add a second battery to their system. Especially if the second battery is close to their amplifiers. If you want to add a second battery, there are a few things that you should know.
If the battery is inside the passenger (in a hatchback vehicle or in a car with a back seat that folds down), you must use a sealed battery (i.e. Optima, Gel Cell). If the battery is being used in the trunk of a vehicle you can use a standard battery but you will need put the battery in a battery box and you will need to provide proper ventillation. Proper ventillation would mean forced air (fan) ventilation from the battery box to the outside of the vehicle. When a standard lead acid battery charges, it produces flammable gases which must be removed from the vehicle to prevent a fire/explosion hazard. This is why you can not, or SHOULD not use this kind of battery in the interior of the vehicle .
The second battery must be fused. The fuse must be as close to the battery as possible (just as you have on the main battery). All of the power for the system must flow through through the fuses (at the batteries) to protect against electrical fires. The diagram below shows the proper fusing and wiring. The fuse at the main battery must be properly rated to protect wire 'A'. The fuse at the second battery must be properly rated to protect wire 'B'.
No matter what kind of battery you use, care must be taken to assure that nothing can come in contact with the battery's terminals. I would strongly recommend putting the battery into a plastic battery box with a cover that can be secured onto the box. The cover can be like the ones used with Marine battery applications.
The ground for the second battery should be grounded to the floor pan of the vehicle. The floor pan is the main piece of sheet metal that forms the largest portion of most new vehicles. This will provide the best return path for the second battery.
Both batteries should be of the same make and model. The CA and CCA should match! Using two different kinds of batteries can cause problems when the car is off. For example, a weak battery can pull current from the stronger battery. However, you can install a relay to separate the two when the car is off, while still running off the additional battery.
Some batteries emit noxious fumes when charging, and is why they and are not to be placed inside the car. If you need to place one in the car, you must use a 100% sealed battery. You can find these on your own.
Many people listen to their stereo without the engine running. This often leads to dead batteries and a vehicle that won't start. A battery isolator will let you completely discharge one battery without discharging the starting battery.
Different Types of Isolators:
There are 2 main types of battery isolators. The diode based type and the relay (solenoid) type. W're only going to cover the Diode based type.
Diode Based Isolator:
This type of isolator is basically two very high current diodes in a heat sink. The diode based isolator has the advantage of long life and trouble free operation but many of the diode based isolators cause a .4 to .6 volt loss which means that the batteries will not charge to as high a voltage as when they are connected directly to the alternator. The diagram below shows the connection for the diode based isolator. Some diode type isolators have a fourth terminal which controls the current flow through the device.
Here is a typical Diode Based Isolator with fuse, and Amplifier connection:
The existing B+ terminal to your battery, goes to the center position of the Isolator. Then your two batteries are connected to the left and right sides.
DUAL BATTERIES WITHOUT AN ISOLATOR
Some people have good results when they add a second battery to their system. Especially if the second battery is close to their amplifiers. If you want to add a second battery, there are a few things that you should know.
If the battery is inside the passenger (in a hatchback vehicle or in a car with a back seat that folds down), you must use a sealed battery (i.e. Optima, Gel Cell). If the battery is being used in the trunk of a vehicle you can use a standard battery but you will need put the battery in a battery box and you will need to provide proper ventillation. Proper ventillation would mean forced air (fan) ventilation from the battery box to the outside of the vehicle. When a standard lead acid battery charges, it produces flammable gases which must be removed from the vehicle to prevent a fire/explosion hazard. This is why you can not, or SHOULD not use this kind of battery in the interior of the vehicle .
The second battery must be fused. The fuse must be as close to the battery as possible (just as you have on the main battery). All of the power for the system must flow through through the fuses (at the batteries) to protect against electrical fires. The diagram below shows the proper fusing and wiring. The fuse at the main battery must be properly rated to protect wire 'A'. The fuse at the second battery must be properly rated to protect wire 'B'.
No matter what kind of battery you use, care must be taken to assure that nothing can come in contact with the battery's terminals. I would strongly recommend putting the battery into a plastic battery box with a cover that can be secured onto the box. The cover can be like the ones used with Marine battery applications.
The ground for the second battery should be grounded to the floor pan of the vehicle. The floor pan is the main piece of sheet metal that forms the largest portion of most new vehicles. This will provide the best return path for the second battery.
Both batteries should be of the same make and model. The CA and CCA should match! Using two different kinds of batteries can cause problems when the car is off. For example, a weak battery can pull current from the stronger battery. However, you can install a relay to separate the two when the car is off, while still running off the additional battery.
Some batteries emit noxious fumes when charging, and is why they and are not to be placed inside the car. If you need to place one in the car, you must use a 100% sealed battery. You can find these on your own.
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