01
Staying at 12 V
A 1000 Ah 12 V bank means 3 kW inverter currents of 250 A and cable you can barely bend. Moving to 24 V halves every current on the boat and doubles the number of DC-DC chargers you can buy off the shelf.
Two hulls, two engines · four aboard · 24 V preferred
Cruising catamaran Lithium Battery System
Two engines, two fridges, a freezer, a watermaker, an inverter that runs the induction hob, and acres of coachroof for solar. Catamarans are the hull where a 24 V system stops being exotic and starts being the only sensible way to keep cable sizes and DC-DC counts under control.
Typical load profile
Two fridges and a freezer110 Ah
Inverter — induction, coffee, tools45 Ah
Watermaker (2 h midday)40 Ah
Instruments, plotter, AIS, radar at anchor22 Ah
Lighting and fans25 Ah
Pumps, devices, autopilot standby18 Ah
Quoted in 12 V amp-hours for comparison; halve the figures for a 24 V bank. Two engines means two alternators, and two DC-DC chargers, or one properly regulated high-output alternator on one engine.
What we would fit · 600–1000 Ah
Budget build
$14,500
600 Ah LiFePO4 at 12 V (or 300 Ah at 24 V)
Two 40 A DC-DC chargers, one per engine
Lithium-profile 60 A mains charger
800 W coachroof solar with two MPPTs
Shunt monitor with logging
Premium build
$26,000
1000 Ah at 12 V equivalent, 24 V system
Externally regulated 150 A alternator on one engine plus DC-DC on the other
3 kW inverter-charger with lithium profile
1.2 kW solar, CAN telemetry to the plotter
Certified install, new compartments, insurer pack
Indicative installed prices, September 2026. At this scale the balance of system — alternators, inverter, solar, cable — costs more than the cells.
On this hull specifically
Battery installation mistakes for this boat type
02
Sizing the bank so the watermaker can run overnight
Run the watermaker at midday while the panels are producing. Scheduling it saves 40 Ah of bank a day, which is 150 Ah of capacity you do not have to buy.
03
Splitting the bank across the hulls badly
Two banks, one per hull, sounds symmetrical and works well. A single bank in one hull with the inverter in the other is a voltage-drop problem waiting for the first long cable run.
04
One BMS for a thousand amp-hours
A single disconnect at that scale takes the whole boat dark. Parallel packs with independent BMSs, each fused, is the standard cruising-cat answer.
Other hulls