How to Wire an RV's Battery Isolator
Simply listening to a vehicle's audio components for an extended period can discharge its battery. In a recreational vehicle (RV), with its complex battery-powered electrical systems, the risk of unintended depletion is much greater. A car that won't start usually involves few problems for towing or jump-starting. A massive RV may present different challenges, and it is thus advisable to have at least two batteries or banks of batteries on board. A correctly-installed isolator, sometimes called a split charge relay, is an electronic device that will prevent coach accessories from discharging the chassis battery when camped.
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Things You'll Need
- Wire, cables and connectors
- Battery isolator
- Fasteners
- Coach battery and securing straps
Instructions
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1
Determine the appropriate gauges of wire, cables and connectors needed. Gauge them to comfortably accept the maximum amperage generated by the charging system when the engine is running. Extended physical lengths demand heavier gauges.
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2
Purchase the appropriate isolator, either diode- or relay-type. Diodes are most reliable and give the longest service but rob a small percentage of the power supplied to the battery from the charging system. Relay (or solenoid) isolators are more complex, and thus more prone to failure, but cause no voltage reduction.
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Fasten the isolator to its permanent location. Considerable heat may be generated as a byproduct of proper function, which must be dissipated safely and effectively.
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Install a deep cycle battery in a location where adequate ventilation is provided and where access is sufficient for safe wiring and fitting securing straps.
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5
Follow the manufacturer's detailed installation instructions. Most isolator looms require alternator power be fed directly to the chassis battery's positive terminal, branched to one of the two heavy studs on the isolator. The studs will be labeled. Another cable, of equal gauge, will run from the isolator's second heavy stud to the positive terminal on the coach battery, from which a feed is run to the coach equipment. Both battery negative terminals must be grounded.
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Tips & Warnings
Isolator studs are as prone to corrosion and verdigris as battery terminals. To defend against long-term corrosion and failure, units manufactured with heavy duty studs are best.
More complex isolators may have a smaller stud, which allows that a manual override be installed as a backup resource. This override will temporarily feed power from the coach battery to the chassis battery in the event of an emergency, such as having parked in extremely cold weather, or something as simple as leaving the sidelights on.
If installing a new coach battery or bank of batteries, deep cycle batteries are designed to serve lower demands for longer periods. Deep cycle batteries are best for operating the coach's domestic appliances.
Only sealed batteries may be installed in passenger areas of any vehicle, which, for the sake of this rule, includes the trunk of an ordinary car. Standard lead/acid batteries create gasses that can explode or catch fire. The batteries MUST be located in a proprietary battery box and be subject to proper ventilation to the outside.
Each battery fitted must be fused. To minimize the risk of an electrical fire, fit the fuse physically close to the battery, and ensure that all power drawn from the battery passes through the fuse. Fuses must be rated accurately, as determined by both demand and wire gauge.
Battery terminals will arc to metal vehicle parts. Always shield both terminals of every battery fitted, so no inadvertent contact can occur.
References
Resources
- Photo Credit rv,motorcoach image by Greg Pickens from Fotolia.com
