BoatHowTo · video

What this video covers

Nigel Calder explains why using a windlass to load-test a battery gives unreliable results.0:50 A viewer proposed running the anchor windlass while measuring voltage at the battery posts to assess three batteries — one engine-start and two 200 Ah house batteries sharing a common earth.0:18 Calder's verdict: the test only identifies a battery in serious failure; it cannot distinguish a partially degraded battery from a healthy one.0:55 A battery in reasonable condition will show a brief voltage dip then flatline, and the windlass cannot run long enough to stress it meaningfully.0:55 A battery that crashes under the load is already severely discharged or has lost most of its capacity.1:09 On the negative-separation question, Calder says disconnecting the common earth is unnecessary — isolating the parallel connection between the two house batteries is sufficient to test each one individually.1:25 A proper battery assessment requires a more systematic load-test method.1:39 The windlass voltage-drop test is a pass/fail screen for dead batteries, not a diagnostic tool for capacity.0:50

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