Mastervolt Tank Level Interface (77030300)

VE.Direct — SmartSolar/BlueSolar MPPTs, SmartShunt, BMV monitors and Phoenix inverters (one official VE.Direct cable per device, 0.3m-10m, right-angle version available for tight spaces). VE.Bus — MultiPlus, MultiPlus-II and Quattro (standard straight-through RJ45 UTP, not crossover). VE.Can — managed batteries and daisy-chained devices (RJ45 with the correct Type A/B BMS cable and an RJ45 terminator at each end of the chain).

Yes — crimped in-house with tinned copper lugs and adhesive-lined heat shrink, 25mm2 to 120mm2, cut to set lengths with your choice of colour and lug hole size. Cable per metre and lugs also sold individually.

Free official Victron app (iOS & Android): cable size and voltage drop calculator, every LED alarm code for Multi/Quattro units, temperature derating, and QR-scan product documentation. Download: https://www.victronenergy.com/support-and-downloads/software#victron-toolkit-app

Start with the product manual — Victron lists the required cable cross-section and DC fuse for every model (MultiPlus-II manual: https://www.victronenergy.com/upload/documents/MultiPlus-II_230V/32424-MultiPlus-II___Quattro-II-pdf-en.pdf, all manuals at victronenergy.com/support-and-downloads/manuals). The maths behind it, from Victron's Wiring Unlimited book: work out the current (watts / battery volts — a 2,400W load is 200A at 12V), then for runs up to 5m use current / 3 = cable size in mm2 (200A / 3 = 66mm2, so 70mm2), and keep total voltage drop under 2.5% (0.3V on 12V, 0.6V on 24V, 1.2V on 48V). Can't get cable thick enough? Double up — 2x 35mm2 equals 70mm2, and larger Victron units have twin battery terminals for exactly this. The free Victron Toolkit app does the calculation for you.

The quick rule from Victron's Wiring Unlimited for runs up to 5m: amps / 3 = cable size in mm2. Work out amps first (watts / volts): a 2,400W inverter on 12V pulls 200A, so 200/3 = 66 - use 70mm2. Then check total voltage drop stays under 2.5% (0.3V at 12V) — the Victron Toolkit app calculates it. Quality rules: fine-stranded flexible cable only (never solid core, coarse strands or AC cable), and for boats or damp installs always tinned-copper marine cable — which is what every cable we crimp uses. If the size you need is unavailable, doubling up is legitimate: 2x 35mm2 = 70mm2.

Classic voltage-drop symptom. Undersized or long cables, a corroded lug, a loose connection or a tired battery all add resistance — under heavy load the voltage AT THE INVERTER sags far below the voltage at the battery, triggering low-voltage or ripple alarms, blowing fuses early, and cooking cables. Victron's test: load the system to maximum, measure voltage at the battery posts and at the inverter's DC terminals — the difference is your voltage drop, and it should be under 2.5%. Fixes, in order: shorten or thicken the battery cables, re-crimp or clean every connection, check fuse/switch/shunt specs, and replace old or undersized batteries. This one issue causes more mystery shutdowns than any inverter fault.

Two ratings matter, and most people only check one. The current rating protects the cable as normal — but lithium batteries can deliver enormous short-circuit currents, far beyond lead-acid, so Victron's Wiring Unlimited also requires the fuse's INTERRUPT rating (breaking capacity) to be equal to or greater than the battery bank's maximum prospective short-circuit current. A fuse with too low an interrupt rating can fail catastrophically instead of breaking the fault. That's why Class T fuses (up to 200kA interrupt) are the go-to for lithium banks, while a standard MEGA fuse (1,000-2,500A interrupt) is only suitable for small systems. Every lithium installation needs at least one fuse in the DC line that meets this — tell us your bank and we'll spec the right fuse and holder.