Battery buying questions
Boat Battery Buying Questions
Compare battery chemistry, fridge runtime, refit cost factors and charger compatibility before choosing a system. Each guide answers one buying question and links to the relevant calculation or installation checks.
- Questions answered
- 6
- Last reviewed
- 4 September 2026
Lithium battery buying and compatibility questions
ComplianceAre Lithium Batteries Allowed on Boats in Australia?Lithium is not prohibited as a chemistry on Australian recreational boats, but installation, licensing and documentation requirements depend on the vessel, jurisdiction, voltage and work performed.ChemistryLithium vs AGM Boat Batteries: Capacity, Weight & ChargingLithium gives you 80% of the label in usable energy against AGM's 50%, at about a third of the weight, and it recharges far faster. AGM costs less on the day and does not care about cold charging.SizingHow Long Will a 100Ah Lithium Battery Run a Boat Fridge?About a day and a half for a typical 12 V marine fridge drawing 5 A at a 45% duty cycle, which is 54 Ah a day against 80 Ah of usable capacity — before the rest of the boat is counted.CostMarine Lithium Refit Cost Factors: What Changes the Quote?Between $900 for a tinnie and $26,000 for a cruising catamaran, installed. On most boats the charging system and wiring cost between a third and a half of the total, and that is not the part to save on.ChargingLithium Battery Solar Controller Compatibility on BoatsOnly with a true lithium profile. A lead-acid charger holds a float voltage lithium does not want, and a desulphation pulse is the sort of thing a BMS disconnects from.BuyingDrop-In vs DIY Lithium Batteries for Boats: Pros & ConsFor most owners, drop-in. A DIY build can be excellent and cheaper, but it makes you the manufacturer for warranty, insurance and survey purposes.