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Battery Systems & Lithium Installation
The lithium revolution has reached cruising boats. LiFePO4 (lithium iron phosphate) batteries deliver significantly more usable capacity per kg and per dollar over a 10-year life than AGM. Most cruiser refits now include or plan a lithium retrofit. This guide covers the components, the cost, and where to get it done.
Lithium retrofit components
- LiFePO4 cells / drop-in batteries: Battle Born, Victron, Renogy, Epoch, others. 100 Ah blocks common.
- BMS (battery management): Built-in (drop-ins) or external (cell-level). Critical for safety.
- Lithium-profile chargers: Shore charger, solar controller, alternator regulator.
- DC-DC converter or alternator protection: Prevents alternator overload from lithium's high charge acceptance.
- Battery monitor: Victron BMV-712, SmartShunt, or equivalent.
- Wiring upgrade: Larger conductors for higher current capability.
- Class T fuses: Safety-critical for lithium.
What it costs
| Component | Common range (USD) | Notes |
|---|---|---|
| 400 Ah LiFePO4 bank (parts) | $2,800–5,500 | 4×100Ah drop-ins |
| 600 Ah LiFePO4 bank | $4,000–8,000 | 6×100Ah |
| Lithium-profile shore charger | $700–1,400 | Victron Multiplus or similar |
| Alternator regulator (Wakespeed/Balmar) | $500–900 | External |
| Solar charge controller | $200–600 | Lithium-capable |
| Battery monitor + shunt | $200–400 | Victron BMV-712 / SmartShunt |
| Class T fuse + holder (per bank) | $80–200 | Safety-critical |
| Pro installation labour | $2,000–5,000 | 40-foot boat |
| Total turnkey lithium retrofit | $8,000–13,000 | Mid-range 400–600Ah |
Frequently asked questions
Lithium vs AGM?
Lithium: half the weight, double usable capacity, 5x faster charge. Pays back in 5–8 years.
Retrofit cost?
DIY $4,000–8,000 parts. Turnkey $8,000–13,000.
Bank size?
Typical 40-foot cruising boat: 300–500 Ah LiFePO4. More for watermaker, air con.
Charging?
Lithium-profile chargers + alternator regulation or DC-DC.
Where installed?
Annapolis, Fort Lauderdale, San Diego, La Paz, Auckland have specialists. DIY increasingly common.