StringCalculator

A dry, ventilated, frost-free room: garage, utility room, cellar. LiFePO4 batteries dislike both frost (charging is forbidden below 0 °C for most of them) and heat (above 35 °C ambient, they age faster). Avoid bedrooms — some inverters fan noisily — and plan for the arrival of the PV cables, the AC cable to the panel, and the earth conductor.

Keep 30 to 50 cm of clearance around the inverter for heat dissipation (check the manual: every manufacturer sets its own distances), and leave room for an extra battery — you almost always end up expanding.

A hybrid inverter weighs 25 to 35 kg, a 48V battery 40 to 50 kg: never fix this to drywall without reinforcement. The ideal is a load-bearing wall (concrete block, concrete) with suitable anchors, or a rack-type frame. If you mount everything on a board, prefer a fire-resistant panel (fiber-cement, Fermacell-type) over bare plywood — you're fixing power electronics to it for 25 years.

Plan the layout before drilling: inverter up top (for reading the screen), DC and AC enclosures on either side, batteries at the bottom on the floor or on a dedicated rack — never hung on the same board as everything else without a structure designed for it.

This is the most dangerous circuit in the system: an inverter charging at 190 A at 48V carries more current than the rest of the house combined. Three rules:

• Cross-section: size for the inverter's max current — in practice 50 mm² up to ~190 A over short runs, 70 mm² beyond that. Short and thick always beats long and thin.
• Protection: a fuse (Mega, NH, or class T depending on current) or a DC breaker as close as possible to the battery +, plus a disconnect switch to isolate the whole thing during maintenance.
• Connections: lugs crimped with a hydraulic press (not a kitchen crimping tool), proper torque, and a heat check with a thermal camera or by hand after the first heavy charge cycles.

Multiple batteries in parallel? Use identical cable lengths for each battery, or better: go through busbars — the batteries then share the current evenly instead of the closest one taking it all.

On the PV (DC) side: disconnect switch, type II DC surge arrester and string fuses (once you have 3 or more strings in parallel) in a dedicated enclosure — this is what the sizing tool calculates for the cable cross-sections.

On the AC side: a dedicated breaker at the main panel, a 30 mA type A residual current device at minimum for the inverter, and an AC surge arrester if your panel doesn't already have one. Every metal part (inverter chassis, battery rack, enclosures) is bonded to the installation's earth.

Rather than connecting the inverter directly to the existing panel, set up a dedicated AC panel inside the energy center, inserted between the main service disconnect (the 500 mA selective one) and the house's electrical panel. Everything passes through it: it does the distributing, and it keeps the system upgradeable.

• Fully wired in 16 mm² flexible cable (H07V-K): much easier to work with in an enclosure than solid core — but flexible wire requires crimped ferrulesat every connection (a dedicated crimping tool, never a bare strand under a screw).
• A 63 A disconnect at the head of the energy center panel, the distribution busbar in the middle, then a 63 A breaker feeding the house panel. If that panel is less than 2 m away from the energy center, go straight there; beyond that, also add a 63 A disconnect at the head of the house panel.
• To connect a central PV inverter (Deye-type): a dedicated feed from the busbar, protected by a type B 300 mA RCD — type B detects the DC-component leakage an inverter can produce, which type A/AC devices can't see.
• From this busbar you can feed a car charger, spa, or sub-panel… Each feed has its own breaker sized for the cable it protects — it's the breaker that protects the cable, never the other way around.

Connect the master battery to the inverter via CAN or RS485 (cable and pinout given in both manuals — pinout varies by brand, which is the classic trap). Then select the right protocol in the inverter's battery menu: the inverter then follows the BMS's actual setpoints instead of fixed voltages.

At commissioning: battery first (precharge if your equipment needs it), then PV, then AC. Check string voltages open-circuit before closing the DC disconnect — a reversed PV polarity is an expensive mistake.

• An undersized battery cable that overheats → losses, or even the start of a fire;
• No fuse between battery and inverter — a short circuit on a 48V battery can weld tools;
• Batteries of different ages or brands mixed on the same busbars without checking BMS compatibility;
• An energy center in a closed, unventilated closet;
• Skimping on the DC surge arrester in a storm-prone area;
• Building everything… without having checked the string sizing first — start there, it's free.