ELECTRONICS

12V/24V Dual Battery Automatic Power Selector

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UPDATED 2026-09-22
EXAMPLE12V/24V Dual Battery Automatic Power Selector
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CASE ANALYSIS

Scenario

A camper van uses a starter battery and a house battery, with an alternator charging the starter battery and a solar panel charging the house battery. An automatic voltage-sensitive relay connects the batteries when the engine runs and isolates them when stopped.

Key decisions

  • Voltage-sensitive relay (VSR) energizes from the alternator output to connect the house battery only while charging.
  • A Schottky blocking diode prevents backfeed from the house battery to the solar panel at night.
  • Separate fuses protect alternator, solar, and house load circuits.

When to reuse this

Use as a reference when designing or troubleshooting dual-battery systems in camper vans, boats, or off-grid vehicles that combine alternator and solar charging.

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