ERD Technical Specifications
Complete battery backup charts for 3-phase Emergency Rescue Devices — 5 KVA to 100 KVA. SMF battery Ah requirements per ERD size and backup duration. Field-validated against 200+ Indian installations.
3-Phase ERD Battery Backup Chart (SMF Lead Acid)
Ah required per backup duration for each ERD KVA rating. These are the minimum Ah values — actual battery count = Ah ÷ battery size × number of strings in series.
| ERD KVA | Bank Voltage | Series Batteries | DC Current (A) | 30 min | 1 hour | 1.5 hrs | 2 hours | 3 hours | 4 hours |
|---|---|---|---|---|---|---|---|---|---|
| 5 KVA | 360V | 30 | 15A | 17 Ah | 28 Ah | 38 Ah | 45 Ah | 65 Ah | 80 Ah |
| 7.5 KVA | 360V | 30 | 19A | 18 Ah | 38 Ah | 45 Ah | 65 Ah | 65 Ah | 120 Ah |
| 10 KVA | 360V | 30 | 25A | 26 Ah | 45 Ah | 65 Ah | 80 Ah | 100 Ah | 125 Ah |
| 15 KVA | 360V | 30 | 38A | 38 Ah | 65 Ah | 88 Ah | 100 Ah | 150 Ah | 180 Ah |
| 20 KVA | 360V | 30 | 50A | 45 Ah | 88 Ah | 100 Ah | 125 Ah | 180 Ah | 240 Ah |
| 30 KVA | 384V | 32 | 65A | 65 Ah | 135 Ah | 180 Ah | 200 Ah | 280 Ah | 360 Ah |
| 40 KVA | 384V | 32 | 85A | 85 Ah | 170 Ah | 230 Ah | 280 Ah | 360 Ah | 450 Ah |
| 50 KVA | 480V | 40 | 105A | 110 Ah | 200 Ah | 280 Ah | 340 Ah | 450 Ah | 560 Ah |
| 100 KVA | 480V | 40 | 200A | 200 Ah | 380 Ah | 520 Ah | 640 Ah | 850 Ah | 1100 Ah |
SMF Battery De-Rating Factors
Lead acid (SMF) batteries cannot deliver their full rated Ah at high discharge rates. Apply these de-rating factors when calculating Ah for short backup durations.
| Backup Duration | De-Rating Factor | Effective Ah = Rated Ah × | Example: 100Ah SMF delivers |
|---|---|---|---|
| 15 min | 0.45 | 0.45 | 45 Ah usable |
| 30 min | 0.52 | 0.52 | 52 Ah usable |
| 1 hour | 0.62 | 0.62 | 62 Ah usable |
| 2 hours | 0.74 | 0.74 | 74 Ah usable |
| 3 hours | 0.8 | 0.8 | 80 Ah usable |
| 4 hours | 0.83 | 0.83 | 83 Ah usable |
| 6 hours | 0.86 | 0.86 | 86 Ah usable |
| 8 hours | 0.88 | 0.88 | 88 Ah usable |
How to Calculate Total Battery Count
e.g. 360V bank = 30 batteries in series (30 × 12V)
e.g. 88 Ah needed, using 100Ah batteries = 1 string (88 ÷ 100 = 0.88, round up to 1)
e.g. 30 series × 1 string = 30 batteries total
e.g. Need 200 Ah with 100Ah batteries: 2 strings → 30 × 2 = 60 batteries total
Real-World Validation
These spec values are validated against actual Indian installations. Key data points:
Data source: Su-Kam/Su-vastika internal battery sizing documentation, verified against field installations 2017–2024. LiftInverter.com is an independent editorial resource. Always commission a site survey before finalising specification.