Blue Sea Add-A-Battery kits use two different components to manage a start battery and a second battery bank: a manual Dual Circuit Plus switch to control the start and house load circuits, and an automatic charging relay (ACR) that can connect the banks when charging is available. The part numbers matter because the smaller 7649 and the 120A 7650/7650003 kits use different switches and relays.
Start and house circuits: a simple system overview
In a typical dual-bank setup the start side supplies the engine starting circuit and the house side supplies accessories. The manual switch keeps those circuits separately controlled in ON; the relay is a second connection between the battery positives and operates automatically. It is important not to confuse the switch's emergency COMBINE function with the ACR's normal charging behaviour.
The manual switch disconnects its two switched load circuits.
Engine and house outputs operate from separate banks. The ACR may independently connect them during charging.
The manual switch joins the banks for temporary emergency starting; the ACR is not intended to carry starter current.
Which Blue Sea kit is which?
| Model number | Automatic charging relay | Manual switch | Format |
|---|---|---|---|
| 7649 | 7601 m-ACR; 65A | 6011 m-Series Dual Circuit Plus | Mini kit |
| 7650 | 7610 SI-ACR; 120A | 5511e e-Series Dual Circuit Plus | Standard kit |
| 7650003 | 7610 SI-ACR; 120A | 5511e e-Series Dual Circuit Plus | Boxed 120A kit |
65A and 120A describe the charging-relay capacity, not the maximum starting current of the battery switch. Blue Sea recommends 7649 for engine charging systems up to 65 amps and 7650 for systems up to 120 amps. For any RV or auxiliary-battery installation, independently check the charging equipment, battery chemistry, fusing, cable sizes and connection requirements.
Included electrical parts and their jobs
| Component | Function | Identification |
|---|---|---|
| 1 — Battery switch | Manually turns the two load circuits OFF/ON or joins the banks in COMBINE. | 6011 for 7649; 5511e for 7650 and 7650003. |
| 2 — ACR | Senses available charging and temporarily connects both battery positives; opens when needed for isolation. | 7601 m-ACR for 7649; 7610 SI-ACR for 120A kits. |
| 3 — Start-isolation connection | Permits the relay to isolate banks during engine cranking when correctly wired. | Follow the corresponding 7601 or 7610 instructions. |
Compare the three kits in our catalog
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Original Blue Sea instructions and installation drawings
The manufacturer provides 7649 mini kit details, 7650 kit details, and 7650003 boxed kit details. For wire-routing, fuse sizing, start-isolation and terminal diagrams, open the 7649 / 7601 installation PDF or the 7650 / 7610 installation PDF. Use the current instructions accompanying the exact kit for the installation.