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1-2-both switch - Cost effective charging system on small boats? 🤔 Ask The Expert with NIGEL CALDER
26 June 2026 · 2 min · 840 views
Nigel Calder explains battery switch positions on a boat
What this video covers
Nigel Calder addresses whether a pontoon boat owner can charge a starter battery and a house battery in parallel through a Perco 1-2-both switch by connecting a charger to one battery.▶ 0:20 Theoretically, parallel charging of batteries with different CCA and amp-hour ratings is wrong, but Calder explains it works in practice because a cranking battery stays near full charge — engine cranking draws only a brief burst of current, quickly replaced by the alternator.▶ 0:46 The house battery absorbs most of the charging current, so the charger should connect to the house battery, not the starter.▶ 1:07 The parallel switch can then top off the cranking battery without significant damage, though it may shorten that battery's life.▶ 1:46 The critical risk: leaving the switch in the parallel position drains both batteries, eliminating starting power.▶ 1:46 Jan Attenstedt recommends a dual-output charger with a dedicated ~3-amp starter-battery output as a cleaner alternative for around $100, removing the need to remember switching discipline.▶ 1:55 The practical takeaway is that the 1-2-both method is a workable, low-cost solution on small boats, but a two-output charger eliminates the main failure mode.
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