What is the purpose of a battery isolator switch, and why is it good practice to use one when leaving a boat unattended for an extended period?

A. Isolator switches exist purely to prevent theft of the battery itself

B. An isolator switch physically disconnects the battery from the boat's electrical circuits — switching it off when leaving the boat unattended prevents small, easily-overlooked parasitic loads (bilge pumps left in "auto," instruments, alarm systems) from silently draining the battery flat over days or weeks, which contributes directly to the sulfation problem covered elsewhere in this section

C. Isolator switches are only fitted to boats with more than one battery bank

D. Using an isolator switch has no relationship to how well a battery holds its charge over time

A. Cold weather alone permanently destroys any lead-acid battery regardless of its charge state

B. A battery left discharged for a long period allows lead sulphate crystals to harden on the plates (sulfation), which reduces the battery's effective capacity and can make it difficult or impossible to fully recharge, even once shore power or a charger is reconnected

C. Batteries left discharged over winter always recover fully with no lasting effect once recharged

D. This issue only affects lithium batteries, never lead-acid types

A. There is no real difference between the two approaches

B. A proper maintenance charger monitors the battery's state and switches between charging and a low-level float/maintenance mode automatically, avoiding both self-discharge over time and the risk of overcharging (which can cause gassing, water loss, or heat damage) that a basic charger left connected indefinitely can cause

C. Maintenance chargers are only relevant to lithium batteries, never lead-acid ones

D. A maintenance charger works only if the battery is fully discharged to begin with