Energy storage systems are built in one of two ways: low-voltage 48 V systems, where battery modules are connected in parallel, and high-voltage systems, where modules are stacked in series to reach hundreds of volts. The choice decides the cables, the safety requirements, the choice of batteries and how the system can grow. Here's the difference and where each design makes sense.
It all comes down to current
Power is voltage multiplied by current: P = U × I. To deliver the same power at a lower voltage, you need proportionally more current.
| Power | Current at 51.2 V | Current at 400 V |
|---|---|---|
| 5 kW | about 98 A | about 12.5 A |
| 10 kW | about 195 A | 25 A |
| 20 kW | about 390 A | 50 A |
Cable losses grow with the square of the current. That's why a 10 kW 48 V system needs short copper cables of 50–70 mm², while a high-voltage system carries the same power over a cable like one for an ordinary socket.
How the two designs work
48 V (LV). Each module is 16 LiFePO4 cells in series, 51.2 V nominal. Modules are connected in parallel: the voltage stays the same while capacity and permitted current grow. To add energy, you add another module to the rack.
High-voltage (HV). Modules are connected in series, raising the battery voltage to hundreds of volts. Ranges differ between manufacturers: Deye's three-phase SG01HP3 inverters, for example, work with batteries from roughly 160 to 700 V, and SolaX X1/X3 G4 hybrids from 80 to 480 V. Capacity is added by stacking more modules within the manufacturer's limits.
Comparison
| Parameter | 48 V | High-voltage |
|---|---|---|
| Current at 10 kW | about 200 A | 20–60 A |
| Battery-to-inverter cables | thick, up to 2–3 m | thinner, length less critical |
| Touch safety | extra-low voltage: shock is unlikely, but arcs and heat are dangerous | hundreds of volts DC — potentially lethal |
| Expansion | add a module in parallel | add a module to the stack, within the series |
| Battery compatibility | wide choice, many manufacturers | usually only the same brand or the compatibility list |
| Efficiency | slightly lower | slightly higher: battery voltage is closer to the inverter's internal bus |
| Installation | within a qualified electrician's scope | trained installers only |
| Cost | lower per kWh | higher, especially up front |
When to choose 48 V
- A house or apartment with an inverter up to 12–15 kW.
- You want to choose batteries from a large market, not from a single manufacturer.
- You plan to grow capacity gradually, module by module.
- The cost per kilowatt-hour matters.
Most home systems in Ukraine are 48 V: Deye's three-phase SG04LP3 series (5–12 kW), for example, works with 40–60 V batteries at up to 240 A. More in the Deye SUN-12K review.
When to choose high-voltage
- 15–20 kW and above: commercial sites, workshops, large homes.
- The battery is far from the inverter, or there's no room for thick cables.
- You're happy with a single-brand ecosystem (inverter and batteries from one maker) — for example, Huawei SUN2000 with 5 kWh LUNA2000 modules.
- Installation and service are done by a certified contractor.
Safety: in a high-voltage battery, even when "switched off" with the button, the modules remain at hundreds of volts relative to each other. Never take the stack apart or disconnect modules yourself — that is a job for an installer with the right training and tools.
Can you combine them?
Not within one system: an inverter is designed for either a low-voltage or a high-voltage battery, and the choice comes with it. So decide on the power and the design first, then the inverter model, and only then the batteries from its compatibility list.
Summary
48 V is the home standard: cheaper kilowatt-hours, free choice of batteries, easier expansion, at the price of thick cables. High-voltage makes sense at high power, where 48 V currents would become impractical, and where a single-brand ecosystem suits you. How to pick the inverter itself is in how to choose an inverter, and cables and protection for 48 V are in the wiring guide.