The Victron Argofet 100-3 is a FET-based battery isolator that charges up to three separate battery banks from a single alternator or DC charger, with no voltage drop penalty. It suits marine, vehicle and off-grid systems where independent battery banks need to stay isolated from each other while sharing one charging source.

Key features

• Three outputs, charges three independent battery banks from one alternator or charger without cross-discharge between banks.
• FET technology, eliminates the 0.6V to 0.7V voltage drop found on diode-based isolators, so each bank gets full charge voltage.
• 100A rating, 100A continuous current across all three outputs.
• Alternator excitation wire, included so the alternator field circuit is not disrupted by the isolator.
• Aluminium housing, compact enough for engine bays and confined spaces.
• Battery chemistry, compatible with lead-acid, AGM, gel and lithium (LiFePO4) batteries.

How it works

Diode isolators drop around 0.6V to 0.7V on every output, which leaves batteries chronically undercharged over time. The Argofet 100-3 uses MOSFET technology to bring that drop close to zero, so each bank receives the voltage the alternator or charger regulator actually set, with no changes needed to the charging source.

Each of the three outputs is fully isolated from the others. A fault or deep discharge on one bank cannot pull current from another, which matters in dual-battery vehicles or multi-bank boats where the starter battery has to stay protected from auxiliary loads. The dedicated alternator excitation connection stops the FET circuitry from preventing the alternator from exciting at startup, so it integrates with standard vehicle and marine alternator systems.

Applications

Used on marine vessels with separate starter, domestic and bow thruster banks, campervans and motorhomes running a starter plus leisure batteries, commercial vehicles with isolated auxiliary systems, off-grid cabins charging multiple banks from one source, and as a retrofit for diode isolators suffering from voltage drop.

Installation notes

Fitting should be carried out by a qualified auto-electrician or marine electrician working with multi-battery DC systems. Disconnect all battery banks before wiring, connect the alternator excitation wire correctly to avoid startup issues, and fuse each output circuit for the connected battery bank and cable rating. For lithium installations, check the BMS is compatible with shared alternator charging before fitting.

What's in the box

• Victron Argofet 100-3 FET battery isolator unit