Sierra BS11030 Battery Switch ā 1-2-Both-Off with AFD
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Sierra BS11030 Battery Switch ā 1-2-Both-Off with Alternator Field Disconnect
Take full control of your boat's electrical system with the Sierra BS11030 ā a heavy-duty marine battery switch built for 12V to 48V DC systems. The 1-2-Both-Off selector lets you choose between two battery banks, run both simultaneously, or isolate the system entirely. The integrated Alternator Field Disconnect (AFD) protects your alternator from voltage spikes when switching under load ā a critical feature for vessels with high-output charging systems.
Housed in a glass fiber-reinforced nylon enclosure rated IP66 and CE certified, this switch is built to handle the marine environment. Removable windows on all four sides make wiring straightforward, and the ergonomic knob can be removed for an added layer of safety and isolation when the vessel is unattended.
Key Specifications
- Maximum Voltage: 48V DC
- Battery Studs: Tin-plated copper, M8 stud size
- Stud Torque: 120 lb.-in
- Recommended Cable Size: 4/0 AWG
- Battery Inputs: 2
- Switch Function: 1-2-Both-Off (4-position)
- Enclosure: Glass fiber-reinforced nylon, IP66 rated
- Certifications: CE certified, ISO 8846 / SAE J1171 Ignition Protected
- Mounting: Surface or panel mount
- Includes: (4) M4Ć35 mounting screws, interchangeable knob labels
Compatible Applications
- Powerboats and center consoles with dual battery banks
- Pontoon boats and deck boats with 12Vā48V electrical systems
- Vessels with high-output alternators requiring AFD protection
- Any marine application requiring ISO 8846 ignition-protected switching
Parts Desk Insights
The BS11030 is the go-to choice when your vessel has two separate battery banks and a high-output alternator. The built-in AFD circuit prevents alternator damage when switching between banks under load ā something a standard battery switch cannot do. If your boat has a single battery bank and no alternator protection requirement, consider the Sierra BS11000 On/Off Disconnect Switch instead. For a single-bank setup that still needs AFD, the Sierra BS11010 On/Off with AFD is the right fit. If you're running dual banks without an AFD requirement, the Sierra BS11020 Dual Battery Selector covers that application. Pair this switch with a properly rated Sierra Marine Battery Fuse on each bank for a complete, code-compliant installation.
Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 1-3 business days.
Special-order items: timeline confirmed after order.
Returns & warranty
Returns & Satisfaction Guarantee
We stand firmly behind the quality of every product we sell. Your confidence matters to us ā and we back it with a straightforward 30-Day Satisfaction Guarantee.
If you are not fully satisfied, you may request a return within 30 days of delivery. All returns must receive pre-approval prior to being sent back. Unauthorized returns will not be accepted.
To qualify for a return:
Item must be in new, unused condition
Product must be in its original packaging
All parts, components, hardware, manuals, and accessories must be included
Packaging must be undamaged and suitable for resale
Important:
Electronics are strictly inspected. No returns on open-box electronics. Exceptions may apply only with prior written approval. Any electronic unit that has been installed, powered, activated, or altered may not be eligible for return.
We are serious about product integrity ā and equally serious about taking care of our customers. If there is ever a product issue, contact us immediately so we can make it right.
For return authorization, please contact our support team before shipping anything back.