Designed on paper, built with my own hands, verified with data.
A 2.32 kW dual-string array feeding a hand-built 8 kWh LiFePO4 bank and two inverters. It runs my home office, my lab, and the majority of the large kitchen appliances when conditions allow — and every watt of it is instrumented in Home Assistant.
System wiring
Solar paths in green, power delivery in amber, monitoring in purple. Animated flows show the direction energy actually moves.
Schematic drawn from live telemetry and confirmed against installation photos: twin Victron BlueSolar MPPT 100/50 (one per string), a 4 kW inverter for the house and a 3.5 kW for the office and shed, red battery selector and shunt. Fusing and busbar detail is simplified here for clarity.
How the cabinet is wired
The DC side in detail — the part the schematic above simplifies. Positive in red, negative in grey, PV in green, AC out in amber.
Two inverters run off the bank: a 4 kW for the house and a 3.5 kW for the office and shed. A 3-way switch engages the pre-charge resistor before the main battery selector closes, soft-starting the inverters. The bank itself is hand-built from LiFePO4 prismatic cells with a JK active-balancing BMS; the SmartShunt on the negative bus feeds current and state-of-charge to Victron VenusOS, and on into Home Assistant.
System at a glance
| Array | Six panels, two strings: 4 × 350 W (1.4 kW) + 2 × 460 W (0.92 kW) — 2.32 kW total |
|---|---|
| Charge control | Two Victron BlueSolar MPPT 100/50 controllers, one per string, each monitored independently |
| Storage | Hand-built 8 kWh LiFePO4 bank — 8S of prismatic cells at 24 V nominal, assembled and balanced myself, protected by a JK active-balancing BMS (JK-B2A8S20P, 200 A), per-cell voltage monitored (typical spread 0.010 V) |
| Inversion | 4 kW pure-sine inverter for the house, plus a 3.5 kW pure-sine inverter for the office and shed |
| Grid assist | 40 A mains charger, scheduled by TightWatt against Octopus Agile half-hourly pricing |
| Monitoring | Victron VenusOS on Raspberry Pi, streamed to Home Assistant over MQTT with self-healing watchdogs |
| Cold weather | Thermostatic battery warmer (on below 10 ℃, off above 12 ℃) protects LiFePO4 charge safety |
| Loads served | Home office, lab/workshop, and the majority of large kitchen appliances when generation and storage allow |
Designed to be extended
-
Original build
Four panels, one battery shed
4 × 350 W string, LiFePO4 bank, inverter and monitoring — designed, mounted, wired and commissioned myself.
-
Expansion
Four panels → six (+2 × 460 W)
Added a second, separately-monitored string of two higher-density panels — taking the roof array from four panels to six and lifting capacity 66% to 2.32 kW, without disturbing the original string.
-
Ongoing
Software squeezes the hardware
TightWatt and the Agile automations mean the same hardware now buys grid energy only in the cheapest half-hours — and gets paid to consume when prices go negative.
A day in the data — 10 July 2026
Straight from the Home Assistant solar dashboard, not a brochure.