High-Power Battery Energy Storage System (BESS)

Making a 2 kW Grid Connection Behave Like a Much Larger Supply

Goal

Transform a property limited to 2 kW from the utility into one capable of supplying many times that power without exceeding the utility limit.

✔ Backup during outages

✔ Automatic battery charging

✔ Peak shaving

✔ Expandable battery bank

✔ Expandable inverter

✔ Solar-ready

System Overview

                    Utility Grid
                  (Maximum 2 kW)
                         │
                         ▼
               ┌───────────────────┐
               │ Smart Hybrid      │
               │ Inverter / BESS   │
               └───────┬───────────┘
                       │
          ┌────────────┴────────────┐
          │                         │
          ▼                         ▼
     House Loads             LiFePO₄ Battery
                                   ▲
                                   │
                           Charges whenever
                        spare grid capacity exists

Power Flow

Load < 2 kW

Grid ─────────────► House

Battery ◄───────── Charging

Load = 4 kW

Grid (2 kW) ──────►

                  ├────► House (4 kW)

Battery (2 kW) ───►

Grid Failure

Grid ❌

Battery ─────────► House

Why This Works

Instead of increasing the grid connection, the battery acts as an energy reservoir.

The grid supplies energy continuously.

The battery stores surplus energy.

Whenever demand exceeds 2 kW, the battery supplies the difference.

Property Demand

        8 kW
         ▲
         │██████████
         │██████████
         │██████████
         │██████████
2 kW ────┼──────────── Grid Limit
         │
         └────────────────────────► Time

Everything above the line
comes from the battery.

Design Philosophy

Grid Limit
   │
   ▼
┌──────────────────────────┐
│ Never exceed 2 kW import │
└──────────────────────────┘
              │
              ▼
┌──────────────────────────┐
│ Store unused energy      │
└──────────────────────────┘
              │
              ▼
┌──────────────────────────┐
│ Use battery for peaks    │
└──────────────────────────┘
              │
              ▼
┌──────────────────────────┐
│ Entire property behaves  │
│ like a larger connection │
└──────────────────────────┘

Maximum Continuous Load

The maximum load depends on four independent limits.

| Limiting Component | Determines | |-------------------|------------| | Utility Connection | Maximum grid import | | Hybrid Inverter | Maximum AC output | | Battery Current | Maximum discharge power | | Battery Capacity | Runtime |

                    Maximum Load

          Smallest Component Wins

       Grid
         │
         ▼
     Inverter
         │
         ▼
      Battery
         │
         ▼
     House Loads

For this design:

Grid            2 kW
Battery         8+ kW
Inverter        10 kVA

Maximum Load

≈ 8 kW Continuous

The battery supplies everything above 2 kW.

Runtime During Outages

Worst case assumes

• Grid completely unavailable • Maximum continuous load

| Battery | 5 kW Load | 8 kW Load | |---------|----------:|----------:| | 10 kWh | ~1.8 h | ~1.1 h | | 20 kWh | ~3.6 h | ~2.2 h | | 30 kWh | ~5.4 h | ~3.3 h | | 40 kWh | ~7.2 h | ~4.4 h | | 60 kWh | ~10.8 h | ~6.6 h |

Runtime

██████████████████ 60 kWh
████████████ 40 kWh
████████ 30 kWh
█████ 20 kWh
███ 10 kWh

Normal Daily Operation

Morning

Grid ─────────► House

Remaining Capacity

──────────────► Battery

Evening

House Load > 2 kW

Grid ──► 2 kW

Battery ─► Remaining Power

Power Failure

Grid ✖

Battery ─────────► Entire House

Recommended Components

                   SYSTEM
                      │
     ┌────────────────┼────────────────┐
     │                │                │
 Hybrid          Battery Bank     Protection
 Inverter

| Component | Recommendation | |-----------|----------------| | Hybrid Inverter | 10 kVA | | Battery | 48 V LiFePO₄ Rack | | Initial Capacity | 20 kWh | | Expansion | 60 kWh | | Battery BMS | Integrated | | DC Fuse | 250–300 A | | DC Isolator | Required | | AC Breakers | Required | | SPD | Type II | | Earthing | Separate battery earth | | Battery Cabinet | Metal rack |

Approximate Budget

| Item | Approx. Cost (₹) | |------|-----------------:| | 10 kVA Hybrid Inverter | 1,20,000 | | 20 kWh LiFePO₄ | 3,50,000 | | Battery Rack | 20,000 | | Protection Equipment | 40,000 | | Wiring & Installation | 50,000 | | Monitoring | 15,000 |

Total

≈ ₹6–7 Lakhs

Future Expansion

Each additional 5 kWh battery

≈ ₹80,000–1,00,000

Safety Architecture

Grid
 │
 ▼
Main Breaker
 │
 ▼
SPD
 │
 ▼
Hybrid Inverter
 │
 ▼
Battery Fuse
 │
 ▼
Battery Disconnect
 │
 ▼
Battery Rack

Every high-current path should have:

✔ Fuse

✔ Breaker

✔ Isolation Switch

✔ Correct cable size

✔ Earthing

✔ Temperature monitoring

✔ Fire extinguisher nearby

✔ Battery cabinet ventilation

Expansion Roadmap

Phase 1

Grid
 │
 ▼
Hybrid Inverter
 │
 ▼
Battery

Phase 2

Solar Panels
      │
      ▼
 MPPT Input
      │
Hybrid Inverter
      │
 Battery

Phase 3

Solar
Generator
Grid

     │
     ▼
Hybrid Inverter
     │
 Battery
     │
 House

Nothing purchased today needs replacing.

Solar simply plugs into the existing inverter.

Future Solar Integration

Current Budget

Solar

❌ Not Installed

Future

Solar Array
     │
     ▼
Hybrid Inverter
     │
     ▼
Battery
     │
     ▼
House

Benefits

✔ Lower electricity bill

✔ Faster battery charging

✔ Longer backup

✔ Off-grid capability

✔ Less battery cycling from grid energy

Smart Features

Phone
  │
  ▼
WiFi / Ethernet
  │
Hybrid Inverter
  │
Battery

Recommended capabilities:

• Live power flow
• Battery SOC
• Grid import/export
• Historical graphs
• Remote firmware updates
• Generator auto-start support
• Home Assistant / MQTT integration
• Automatic load shedding