SISV-4.2K-H(TWIN) Hybrid inverter 4.2kW 1Ф (battery 24V)

The single-phase off-grid/hybrid inverter SISV-4.2K-H(TWIN) from Veichi provides a 4.2 kW continuous output capacity designed for low-voltage 48V battery systems. It handles a combined solar/utility charging current of up to 120A, transitions to backup power in less than 10 ms, and features 2 independent MPPT trackers for multi-directional PV string setups. The specialized "TWIN" series configuration includes dual AC outputs, enabling intelligent smart-load power management during outages.

Typical Applications:

• Emergency home power backup with dedicated smart-load separation for major household appliances.
• Off-grid solar installations for remote cottages or telecom units using low-voltage LiFePO4 or lead-acid storage.
• Grid-tied hybrid setups needing automated prioritization of critical consumer groups during load shedding.

Critical Warning: Operating at a 48V nominal rating with charging currents up to 120A demands premium copper DC battery cables of 35-50 mm² and a high-quality inline 150A fuse. Always program the appropriate Veichi BMS protocol maps to prevent communication faults.

Veichi SI — hybrid solar inverter for off-grid and backup power

SI is Veichi's range of single-phase hybrid inverters, 3–10.2 kW (220/230 V output, 50/60 Hz). It combines solar panels, a battery and the grid in one box: by day it draws from the panels, sends the surplus to the battery, and keeps the grid as backup. It's used on private homes, country houses, small farms and any site that needs to ride through outages.

The built-in MPPT controller works in a 60–450 V window (500 V DC max input), with conversion efficiency up to 97%. The battery is 24 or 48 V. For lithium batteries you set the type to LIB in the menu: the inverter activates lithium within 3 seconds and brings up the BMS link over the PACE protocol.

What SI is good for

• Home backup (3–6 kW): on a grid outage it switches to the battery without a break for critical loads. Size it with headroom for inrush — a pump or compressor draws 3–5× its rating at start.
• Off-grid system: panels + battery with no grid at all — a farm, a pump house, a remote site.
• Hybrid with daytime self-consumption: by day it runs on solar, the battery charges, the grid is a fallback.
• 8–10.2 kW sites (TWIN): the larger models in the series for bigger loads.

Source-priority modes (verified against the manual)

In practice, in summer people run Solar First or SBU (maximum from the sun); in winter, with weak generation, Utility First so the battery isn't drained to zero. It switches from the LCD panel in seconds.

What to know before installation

• Battery type — LIB: for lithium set the type to LIB, then the inverter activates the battery and brings up the PACE BMS link. For lead-acid there's a separate profile with charge voltages. Compatible lithium batteries are in the battery catalog.
• BMS handshake with lithium batteries: if the battery "isn't seen" over the link, it's almost always the CAN/RS485 pinout and the protocol choice for the specific battery maker. A field walkthrough (including Felicity): Veichi inverter–BMS handshake.
• Grid sensitivity: the AC input works in roughly 195–253 V. On weak rural grids with dips the inverter may switch to the battery more often — that's normal behavior, not a fault.
• MPPT window 60–450 V: build the panel string so the voltage stays in this range (500 V max input). A string that's too short falls out of the MPPT window on an overcast day — generation drops.
• Connection order: battery first, then the solar panels and grid — never feed panels into the inverter without the battery connected.

When SI is NOT the right choice

• Three-phase load or power above 10 kW — you need the three-phase Veichi VH hybrids
• Motor control only (no solar/battery) — that's an ordinary VFD, see Veichi AC10/AC310
• An industrial grid-tied solar plant without storage — you need an on-grid inverter, not a hybrid

Our experience

Most people contact us after the install — "the inverter doesn't see the lithium battery". Nine times out of ten it's not a fault but a mismatched BMS link: the wrong protocol or a swapped CAN pinout. So we suggest matching the battery model to the inverter already at the selection stage. The full series catalog is here — Veichi hybrid inverters; a step-by-step BMS connection walkthrough is in a dedicated guide.