---
product_id: 3836439
title: "Blue Sea Systems 7650 Add-A-Battery Kit - Dual Circuit Battery Management System, 120 Amps"
brand: "blue sea systems"
price: "142381 Ft"
currency: HUF
in_stock: true
reviews_count: 9
category: "Blue Sea Systems"
url: https://www.desertcart.hu/products/3836439-blue-sea-systems-7650-add-a-battery-kit-dual-circuit
store_origin: HU
region: Hungary
---

# Automatic battery isolation Emergency battery combine feature 120A continuous rating Blue Sea Systems 7650 Add-A-Battery Kit - Dual Circuit Battery Management System, 120 Amps

**Brand:** blue sea systems
**Price:** 142381 Ft
**Availability:** ✅ In Stock

## Summary

> 🔋 Power up your adventure with smart, seamless dual battery control!

## Quick Answers

- **What is this?** Blue Sea Systems 7650 Add-A-Battery Kit - Dual Circuit Battery Management System, 120 Amps by blue sea systems
- **How much does it cost?** 142381 Ft with free shipping
- **Is it available?** Yes, in stock and ready to ship
- **Where can I buy it?** [www.desertcart.hu](https://www.desertcart.hu/products/3836439-blue-sea-systems-7650-add-a-battery-kit-dual-circuit)

## Best For

- blue sea systems enthusiasts

## Why This Product

- Trusted blue sea systems brand quality
- Free international shipping included
- Worldwide delivery with tracking
- 15-day hassle-free returns

## Key Features

- • **Emergency Power Combine:** Instantly merge battery power for jump starts or high-demand situations with a simple switch.
- • **Plug-and-Play Simplicity:** Streamlines dual battery management with intuitive switching—no more guesswork or manual toggling.
- • **Smart Start Battery Protection:** Automatically isolates your engine start battery to safeguard sensitive electronics during ignition.
- • **Corrosion-Resistant Connectivity:** Tin-plated copper studs ensure maximum conductivity and long-lasting durability in marine environments.
- • **Effortless Dual Battery Charging:** Seamlessly charges two batteries from one source without extra regulators or isolators.

## Overview

The Blue Sea Systems 7650 Add-A-Battery Kit is a robust dual circuit battery management system rated for 120 amps, designed to efficiently charge two batteries from a single source while protecting your start battery. Featuring automatic isolation, an emergency combine function, and corrosion-resistant tin-plated copper studs, this compact kit simplifies battery switching and enhances reliability for marine and off-road applications.

## Description

Upgrade your boat’s electrical system with the Blue Sea Systems Add-A-Battery Kit, designed to simplify battery management and maximize performance. Ideal for outboard-powered boats with alternator outputs up to 120A, this compact kit ensures your engine start battery stays protected while efficiently charging your house battery.

Review: 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.
Review: This is an excellent kit for adding a battery to your 4x4 - This is an excellent kit for adding a battery to your 4x4. While it is designed for marine use, it's perfect for mounting under the hood and controlling a second battery. The smart relay is particularly clever, being able to sense a charging voltage on either side of the relay. So for instance, when it senses charge from your alternator on your #1 battery, it will close the relay and and charge the #2 battery. Similarly, if the solar system is charging the #2 battery, once it's full the relay will sense a charging voltage and close the relay and charge the #1 battery. The relay can also be turned off with the charge isolation circuit, so this is a very smart relay indeed. The switch is actually optional, but it allows some particularly handy options. Depending on how you wire it, you can use the switch to turn off the whole system, to use both batteries independently and to electrically combine both batteries through the high current switch. Combining the batteries would allow a self jump start in the event of a dead battery, or to increase the power available when winching. Realize with this kit you will still need appropriate wiring, fuses at the batteries, a ground bus, and several hours to install properly. You will also need some understanding of electrical circuits and how they work. There are several equally good and safe ways to install the add a battery kit. There is a recommended circuit diagram in the included instructions, and there are several other slightly different variations on Blue Sea's website. I thought both the included instructions and the website information very helpful. In summary this is a high quality and robust kit from a high quality company. HIGHLY RECOMMENDED.

## Features

- Allows two batteries to be efficiently charged from a single charging source without external regulators or isolators
- Automatically isolates house battery during starts to protect electronics
- Provides an emergency combine feature to draw power from both batteries
- Simplifies switching for two battery systems
- Tin plated copper studs on the battery switch provide maximum conductivity and corrosion resistance

## Technical Specifications

| Specification | Value |
|---------------|-------|
| ASIN | B000RZNP5K |
| Batteries | 1 Unknown batteries required. |
| Best Sellers Rank | #43,705 in Automotive ( See Top 100 in Automotive ) #110 in Automotive Replacement Battery Switches |
| Date First Available | October 1, 2001 |
| Department | mens |
| Is Discontinued By Manufacturer | No |
| Item Weight | 1.5 pounds |
| Item model number | 7650 |
| Manufacturer | Blue Sea Systems |
| Product Dimensions | 6 x 5 x 4 inches |

## Product Details

- **Brand:** Blue Sea Systems
- **Color:** Black
- **Item Weight:** 1.5 Pounds
- **Product Dimensions:** 12"D x 9"W x 5"H
- **Specification Met:** Etl, Ip54

## Images

![Blue Sea Systems 7650 Add-A-Battery Kit - Dual Circuit Battery Management System, 120 Amps - Image 1](https://m.media-amazon.com/images/I/81-AL2+wQiL.jpg)
![Blue Sea Systems 7650 Add-A-Battery Kit - Dual Circuit Battery Management System, 120 Amps - Image 2](https://m.media-amazon.com/images/I/81vax3SRJdL.jpg)
![Blue Sea Systems 7650 Add-A-Battery Kit - Dual Circuit Battery Management System, 120 Amps - Image 3](https://m.media-amazon.com/images/I/61fxcfOvU2L.jpg)
![Blue Sea Systems 7650 Add-A-Battery Kit - Dual Circuit Battery Management System, 120 Amps - Image 4](https://m.media-amazon.com/images/I/71iT+gG9xdL.jpg)

## Customer Reviews

### ⭐⭐⭐⭐⭐ Two ways to wire it up.
*by C***T 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.

### ⭐⭐⭐⭐⭐ This is an excellent kit for adding a battery to your 4x4
*by A***K on March 9, 2015*

This is an excellent kit for adding a battery to your 4x4. While it is designed for marine use, it's perfect for mounting under the hood and controlling a second battery. The smart relay is particularly clever, being able to sense a charging voltage on either side of the relay. So for instance, when it senses charge from your alternator on your #1 battery, it will close the relay and and charge the #2 battery. Similarly, if the solar system is charging the #2 battery, once it's full the relay will sense a charging voltage and close the relay and charge the #1 battery. The relay can also be turned off with the charge isolation circuit, so this is a very smart relay indeed. The switch is actually optional, but it allows some particularly handy options. Depending on how you wire it, you can use the switch to turn off the whole system, to use both batteries independently and to electrically combine both batteries through the high current switch. Combining the batteries would allow a self jump start in the event of a dead battery, or to increase the power available when winching. Realize with this kit you will still need appropriate wiring, fuses at the batteries, a ground bus, and several hours to install properly. You will also need some understanding of electrical circuits and how they work. There are several equally good and safe ways to install the add a battery kit. There is a recommended circuit diagram in the included instructions, and there are several other slightly different variations on Blue Sea's website. I thought both the included instructions and the website information very helpful. In summary this is a high quality and robust kit from a high quality company. HIGHLY RECOMMENDED.

### ⭐⭐⭐⭐⭐ It’s a problem solver when you buy the best you get the best
*by M***R on August 10, 2025*

I kept having problems once I switched this no problems occurred at all. It is really awesome piece of equipment.

## Frequently Bought Together

- Blue Sea Systems Add-A-Battery Kit
- Blue Sea Systems - Battery Switch ON/Off AFD
- BOJACK MEGA Car Fuse Holder for ANM Bolt-on Fuse (Pack of 2 Pcs)

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*Product available on Desertcart Hungary*
*Store origin: HU*
*Last updated: 2026-03-07*