The cheapest part of the job
Marine Battery Fuses and Circuit Protection
This is the least expensive category on the site and the one an insurer will ask about first. A lithium bank will deliver a fault current that a standard blade or ANL fuse cannot safely interrupt, which is why a Class-T fuse at the bank terminal is the specification. Get this wrong and nothing else on the boat matters.
How to size a fuse
- A Class-T fuse at the bank terminal, rated above your maximum continuous current and below the cable's capacity.
- Interrupt rating is the point: a fuse that cannot break the fault current is decoration.
- Every charge source and every load gets its own protection, sized to its own cable.
- This is the one category where you follow the electrician, not the internet — including this page.
The full reasoning is in Marine Lithium Battery Wiring: Cable and Fuse Protection.
Sized for your boat
400 A
Fuse rating for a 400 Ah bank
A starting point, not a specification. The correct fuse rating comes from the cable you actually run and its length, not from the bank alone. Have a suitably qualified person check the design against AS/NZS 3004.2 and the licensing rules that apply to your vessel and jurisdiction.
Closest rating we list
The options
Compare equipment ratings and applications
| Product | Fuse rating | Price band | Best suited to |
|---|---|---|---|
| Blue Sea Systems Class-T 200 A | 200 A | $90–$150 | Banks up to about 200 Ah with a modest inverter. |
| Blue Sea Systems MRBF terminal 300 A | 300 A | $45–$80 | Protecting individual charge sources and feeds close to the battery. |
| Blue Sea Systems Class-T 400 A | 400 A | $130–$210 | 400 Ah and larger banks with a substantial inverter. |
Head to head
Asked most
Why a Class-T fuse and not an ANL?
Interrupt rating. A lithium bank can deliver a fault current a standard ANL cannot safely break, which means the fuse fails without clearing the fault. A Class-T is rated to interrupt it.
What size fuse for my bank?
Above your maximum continuous current and below the cable's capacity. That is a calculation your installer signs against, and it depends on cable size and run length as much as on the bank.