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Blue Sea Systems 7650 Add-A-Battery Kit

4.8 4.8 out of 5 stars 588 ratings

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Battery Kit
120A DC

Purchase options and add-ons

Brand Blue Sea Systems
Size No Size
Item Weight 1.5 Pounds
Terminal Through Hole
Vehicle Service Type
Boat
Voltage
12 Volts

About this item

  • Don't get stranded - Add a Battery
  • Simplifies switching; Isolates engine and house circuits; Combines batteries for emergency starting
  • Shares the charge between two batteries more efficiently than a battery isolator
  • Tin-plated copper studs for maximum conductivity and corrosion resistance
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Important information

Visible screen diagonal

1" / 3 cm

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From the manufacturer

-

Blue Sea Systems Add-A-Battery Kit

Product Details

The ADD-A-BATTERY is as simple to operate as an ON-OFF switch, yet effectively manages the switching and charging of two batteries from a single charge source

The Add-A-Battery includes a Dual Circuit Plus Battery Switch and an Automatic Charging Relay. These components simplify switching and automate charging, so that all you have to do is turn the battery switch ON when you arrive and OFF when you leave.

Dual Circuit Plus Battery Switch

  • Simplifies switching
  • Isolates engine and house circuits
  • Combines batteries for emergency starting
  • Tin-plated copper studs for maximum conductivity and corrosion resistance

ACR Automatic Charging Relay

  • Automatically combines batteries during charging
  • Isolates batteries during engine cranking and when not charging
  • Shares the charge between two batteries more efficiently than a battery isolator
  • Allows efficient dual battery charging without needing regulator adjustment or rewiring

What's in the box

  • Blue Sea Systems 7650-BSS Add-A-Battery Kit -120A
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    Product information

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    Product Description

    Adding a second battery to the electrical system prevents the unintended discharge of the engine start battery. Blue Sea Systems popular Add-A-Battery kit was primarily designed for boats with alternator output of 120A or less. When installed, the Add-A-Battery isolates the start battery from the house loads which prevents the discharge of the start battery. The Add-A-Battery offers a simple way to control the charging and battery switching of two battery banks. The E-Series Dual Circuit Plus Battery Switch simplifies the switching while the SI-ACR automates charging between two batteries.

    Customer reviews

    4.8 out of 5 stars
    4.8 out of 5
    588 global ratings

    Customers say

    Customers like the quality, performance, ease of installation, and battery of the electronic switch. For example, they mention it's well-made, works great for their needs, and is easy to install. That said, some appreciate the ability to combine batteries if needed.

    AI-generated from the text of customer reviews

    44 customers mention44 positive0 negative

    Customers are satisfied with the quality of the electronic switch. They mention that it is well-made, and easy to install. Customers also appreciate the simplicity and the ease of setup. Overall, customers are happy with their purchase and recommend it to others.

    "...For the product itself, it is very solidly made, and has been working flawless...." Read more

    "...In summary this is a high quality and robust kit from a high quality company. HIGHLY RECOMMENDED." Read more

    "...One battery to run the ACC. One battery for the engine. Great kit and easy to install. Really saves my battery...." Read more

    "Blue Sea systems makes quality products this is my second one for a boat this time...." Read more

    39 customers mention29 positive10 negative

    Customers find the installation of the electronic switch to be easy. They mention that the instructions are good, simple, and simple. Some say that the system was easy to install and that the included instructions have a recommended circuit diagram.

    "...SIMPLE SIMPLE SIMPLE." Read more

    "...There is a recommended circuit diagram in the included instructions, and there are several other slightly different variations on Blue Sea's website..." Read more

    "...One battery for the engine. Great kit and easy to install. Really saves my battery. Gives me peace when long days out on the lake...." Read more

    "Works exactly as described and easy to install. Helps keep your boats battery banks charged." Read more

    39 customers mention39 positive0 negative

    Customers are satisfied with the performance of the electronic switch. They say that it works great for their needs, is functional, and is a great device. Customers also appreciate the automatic switch and the optional switch, which allows for some particularly handy options.

    "...For the product itself, it is very solidly made, and has been working flawless...." Read more

    "...The switch is actually optional, but it allows some particularly handy options...." Read more

    "Works exactly as described and easy to install. Helps keep your boats battery banks charged." Read more

    "This works great for my needs...." Read more

    22 customers mention19 positive3 negative

    Customers like the battery. They say it's a great feature that allows them to run independently. They like that the battery can be combined if needed, and that it keeps both batteries charged. Some like that it prevents anything on the boat from draining both. Overall, customers are happy with the product and recommend it to others.

    "This is an excellent kit for adding a battery to your 4x4...." Read more

    "...One battery to run the ACC. One battery for the engine. Great kit and easy to install. Really saves my battery...." Read more

    "Used all summer and it performed as it should, both batteries were able to run independently until charging required. No issues" Read more

    "...Keeps both batteries charged and prevents anything on the boat from draining both batteries. No more being stranded because of a dead battery." Read more

    Two ways to wire it up.
    5 Stars
    Two ways to wire it up.
    After much reading and actually calling and talking to Blue Sea's tech support I'm very impressed with this product and their support. I know others have worried about the small voltage drain from the ACR unit. The ACR unit uses a small amount of current and over a VERY long time and it can drain the batteries it’s monitoring. I talked to the Blue Sea's Tech about this, and they had estimated about 4 months of just sitting there monitoring the battery voltage before the voltage drop would start to cause problems starting the engine. (This would depend of course on the condition of the battery and size/rating of it). However, when talking to the tech about this, there are a few things you can do to completely turn off the ACR. First if you hook it up like they show in the product picture you will need to hook up a small toggle switch to one of the three spade connectors on the unit to turn it off. Or if you are like me and want to KNOW everything is turned off when you put your boat away, you can wire as I have diagramed in the picture attached. By putting the ACR on the "downstream" side of the switch, you can turn everything off when you turn off the main switch. This will still allow the ACR to monitor the batteries when you have the boat in use and will function normally. The only thing would be if you put a charger on one of the batteries when in storage, you would want to leave the master switch to the “on” position so the ACR could function and allow current from one battery to the other. Otherwise, if you had the master switch in the off position you would only be charging the one battery that the charger is hooked up to. The batteries would be isolated from each other and from the ACR.Also, when I was speaking to the tech I mentioned I was I was worried about the 120 amp rating of the unit when the ACR engages. If there is a big voltage differential between the two batteries, there would be a surge of current across the ACR when it connects the two batteries. This 120 Amp is a continuous rating and the ACR will not engage the circuit if there is too big of voltage difference. This would be a case where one battery is bad, has a bad cell or has an extremely high load on it and cannot maintain a high enough voltage. The ACR will disengage and will try to isolate the batteries in that case. In continuous operation the ACR would really only see the total amount of output that the alternator could generate. In my case this is about 100 amps so the 120 amp ACR unit is sufficient.For the product itself, it is very solidly made, and has been working flawless. I had a Pergo basic 1, 2, 1+2, Off switch in my boat, and got tired of trying to remember to flip the switch to 1 when anchored out, then back to 1+2 when cruising around. With this no need for any of that. Just turn the main switch on when I’m getting all the stuff loaded in, and off when we put it in storage. SIMPLE SIMPLE SIMPLE.
    Thank you for your feedback
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    Top reviews from the United States

    Reviewed in the United States on January 3, 2017
    Pattern Name: Battery KitStyle: 120A DCVerified Purchase
    Customer image
    5.0 out of 5 stars Two ways to wire it up.
    Reviewed in the United States on January 3, 2017
    After much reading and actually calling and talking to Blue Sea's tech support I'm very impressed with this product and their support. I know others have worried about the small voltage drain from the ACR unit. The ACR unit uses a small amount of current and over a VERY long time and it can drain the batteries it’s monitoring. I talked to the Blue Sea's Tech about this, and they had estimated about 4 months of just sitting there monitoring the battery voltage before the voltage drop would start to cause problems starting the engine. (This would depend of course on the condition of the battery and size/rating of it). However, when talking to the tech about this, there are a few things you can do to completely turn off the ACR. First if you hook it up like they show in the product picture you will need to hook up a small toggle switch to one of the three spade connectors on the unit to turn it off. Or if you are like me and want to KNOW everything is turned off when you put your boat away, you can wire as I have diagramed in the picture attached. By putting the ACR on the "downstream" side of the switch, you can turn everything off when you turn off the main switch. This will still allow the ACR to monitor the batteries when you have the boat in use and will function normally. The only thing would be if you put a charger on one of the batteries when in storage, you would want to leave the master switch to the “on” position so the ACR could function and allow current from one battery to the other. Otherwise, if you had the master switch in the off position you would only be charging the one battery that the charger is hooked up to. The batteries would be isolated from each other and from the ACR.

    Also, when I was speaking to the tech I mentioned I was I was worried about the 120 amp rating of the unit when the ACR engages. If there is a big voltage differential between the two batteries, there would be a surge of current across the ACR when it connects the two batteries. This 120 Amp is a continuous rating and the ACR will not engage the circuit if there is too big of voltage difference. This would be a case where one battery is bad, has a bad cell or has an extremely high load on it and cannot maintain a high enough voltage. The ACR will disengage and will try to isolate the batteries in that case. In continuous operation the ACR would really only see the total amount of output that the alternator could generate. In my case this is about 100 amps so the 120 amp ACR unit is sufficient.

    For the product itself, it is very solidly made, and has been working flawless. I had a Pergo basic 1, 2, 1+2, Off switch in my boat, and got tired of trying to remember to flip the switch to 1 when anchored out, then back to 1+2 when cruising around. With this no need for any of that. Just turn the main switch on when I’m getting all the stuff loaded in, and off when we put it in storage. SIMPLE SIMPLE SIMPLE.
    Images in this review
    Customer image Customer image
    Customer imageCustomer image
    143 people found this helpful
    Report
    Reviewed in the United States on March 9, 2015
    Pattern Name: Battery KitStyle: 120A DCVerified Purchase
    53 people found this helpful
    Report
    Reviewed in the United States on September 13, 2023
    Pattern Name: Battery KitStyle: 120A DCVerified Purchase
    Customer image
    5.0 out of 5 stars Great kit if adding a battery.
    Reviewed in the United States on September 13, 2023
    I picked this up to add a battery to my Malibu. One battery to run the ACC. One battery for the engine. Great kit and easy to install. Really saves my battery. Gives me peace when long days out on the lake. Knowing i wont be caught dead in the water.
    Images in this review
    Customer image
    Customer image
    One person found this helpful
    Report
    Reviewed in the United States on July 8, 2023
    Pattern Name: Battery KitStyle: 120A DCVerified Purchase
    Reviewed in the United States on January 23, 2013
    Pattern Name: Battery KitStyle: 120A DCVerified Purchase
    2 people found this helpful
    Report
    Reviewed in the United States on November 25, 2023
    Pattern Name: Battery KitStyle: 120A DCVerified Purchase
    Reviewed in the United States on November 28, 2023
    Pattern Name: Battery KitStyle: 120A DCVerified Purchase

    Top reviews from other countries

    Evan R
    5.0 out of 5 stars fantastic delivery
    Reviewed in Australia on April 16, 2021
    Pattern Name: Battery KitStyle: 120A DCVerified Purchase
    Customer
    5.0 out of 5 stars Best on the market for the value
    Reviewed in Canada on January 8, 2021
    Pattern Name: Battery KitStyle: 120A DCVerified Purchase
    Dugal McFarlane
    3.0 out of 5 stars Quality item but check size and be prepared to buy a lot more bits.
    Reviewed in Australia on March 13, 2021
    Pattern Name: Battery KitStyle: 120A DCVerified Purchase
    One person found this helpful
    Report
    Michael J. Hughes
    5.0 out of 5 stars Excellent build quality
    Reviewed in the United Kingdom on November 2, 2013
    Pattern Name: Battery KitStyle: 120A DCVerified Purchase
    One person found this helpful
    Report
    Bosso
    5.0 out of 5 stars Is a reasonable price...will be easy to install with bit of wire testing and installation tools
    Reviewed in Canada on September 17, 2022
    Pattern Name: Battery KitStyle: 120A DCVerified Purchase
    One person found this helpful
    Report