The Victron BCD 802 is a diode-based battery combiner that charges two separate battery banks from a single charging source, without letting one bank discharge into the other. It suits marine, vehicle and off-grid setups where a starter battery needs to stay isolated from a service or leisure bank.

Key features

• Battery combiner, combines two battery banks from one charging source using Schottky diodes, blocking reverse current flow between them.
• Current rating, 80A continuous, covering most alternator and charger outputs on 12V and 24V systems.
• Two outputs, keeps starter and leisure or service batteries electrically isolated during discharge.
• Weight, 0.49 kg, compact enough for engine bays and vehicle battery compartments.
• Passive design, no moving parts, no relays and no control electronics, so there's nothing to maintain.

How it works

Current flows from the charging source to both battery banks at the same time, while the diodes stop current flowing back from one bank into the other. A flat service battery can't drain the starter battery, and the reverse holds true too. Schottky diodes are used here rather than standard silicon ones, giving a lower forward voltage drop and less heat generated during charging. That voltage drop, typically 0.3V to 0.6V for Schottky types, needs to be factored into the charging voltage set at the source, especially with lithium batteries where the charge voltage tolerance is tight.

Applications

Marine installations needing isolation between an engine start battery and a domestic bank. Motorhomes and campervans running a split-charge arrangement between the vehicle starter and leisure batteries. Light commercial vehicles with auxiliary banks for refrigeration or equipment. Off-grid cabins or vehicles where one solar charge controller or alternator feeds two separate banks, and backup systems where two banks need to discharge independently from a single charger.

Installation notes

Mount the BCD 802 somewhere well ventilated, since the diodes generate heat under load, and make sure the mounting surface can dissipate that heat at sustained high currents. Wiring on each output should be rated for the maximum current and protected with a correctly sized fuse. Because of the diode voltage drop, the charging source voltage may need a slight increase to compensate, particularly with AGM or lithium chemistries. Fitting should be carried out by a qualified auto-electrician or marine electrician who understands multi-battery systems.

What's in the box

• 1 x Victron BCD 802 diode battery combiner