How to Plan Marine Lithium House Battery Bank Wiring

Equipment and information required

• Class-T fuses, one per pack
• Tinned marine cable sized for the load
• A shunt-based battery monitor
• Crimping tool and heat-shrink lugs

How to Plan Marine Lithium House Battery Bank Wiring: steps

1. 01

   Isolate everything before you start

   Shore power off, solar covered or isolated at the controller, engine start disabled, and the old bank disconnected negative-first. A lithium bank has no off switch of its own.

2. 02

   Fuse each pack at its own terminal

   A Class-T fuse, or equivalent interrupt rating, as close to each pack's positive terminal as practical. Parallel packs behind a single bus fuse are not protected from a fault inside one of them.

3. 03

   Use equal-length cables to the bus

   Packs in parallel share current in proportion to the resistance of their path. Unequal cable lengths mean one pack works harder, ages faster and fails first. Same length, same size, every pack.

4. 04

   Put the shunt on the negative, in the right place

   The shunt goes between the bank's negative and every other negative in the boat, with nothing else connected to the battery side of it. Anything wired to the wrong side of the shunt is invisible to the monitor.

5. 05

   Size every run for the new currents

   The inverter's continuous rating, the DC-DC charger's output, the windlass under load. Then check each run again for voltage drop over its round-trip length and take the larger cable.

6. 06

   Terminate properly

   Crimped, heat-shrunk, tinned lugs, torqued to specification, no more than four connections on a stud. Support the cable so its weight is not carried by the terminal.

7. 07

   Commission before you leave it

   Set the charge voltages to the pack's specification, calibrate the monitor at a known full charge, and write down the wiring diagram and fuse ratings while it is all still visible.

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