FAQ: Lithium Battery UPS Discharge Characteristics & Overload
Last updated 2026-08-25
A lithium battery UPS built on LiFePO4 chemistry behaves very differently from a legacy lead-acid unit during discharge and overload events. This FAQ explains the flat discharge plateau, high-rate capability, overload handling, ET series ratings, LD48 discharge characteristics, and power-factor matching.
1. LiFePO4 discharge platform vs lead-acid voltage sag?
LiFePO4 cells hold a flat 3.2 V nominal across most of their capacity, so a High Idea Power Lithium Battery UPS keeps its DC bus and AC output stable from 100% SOC down to near-empty. The LD48 packs run at 48 V nominal (16 cells in series), charge to 57 V and discharge to a 40 V cutoff. A lead-acid string sags almost linearly from ~2.1 V/cell to 1.75 V/cell, forcing the inverter to boost a falling DC voltage. The flat lithium plateau keeps full load capacity available longer before the low-voltage alarm.
2. C-rate / high-current discharge capability?
The LD48 series — LD4810 (10 Ah), LD4820 (20 Ah), LD4830 (30 Ah), LD4850 (50 Ah) — uses high-power LiFePO4 cells supporting high-rate discharge. A 50 Ah LD48-50 delivers full rated UPS load at its stable 48 V plateau, while an equivalent lead-acid string would need over-sizing to avoid voltage collapse under high current.
3. Short-term overload and transfer to bypass?
An ET-series online double-conversion Lithium Battery UPS runs its inverter continuously, so the DSP manages overload: brief overloads are absorbed by the inverter, a sustained overload transfers to bypass to protect the power stage, and the unit returns to line mode when load drops. Because the inverter is always on, there is no break on line/battery switchover.
4. ET series overload and power ratings?
The ET series is rated at 0.8 power factor, so real watts are 80% of the VA figure:
| Model | Rating | Battery | Notes |
|---|---|---|---|
| ET1K | 1000 VA / 800 W | 36 V 15 Ah Li | Tower, RS232 |
| ET2K | 2000 VA / 1600 W | 48 V 20 Ah | RS232 |
| ET3K | 3000 VA / 2400 W | 48 V 30 Ah | RS232 |
| ET6KRS | 6000 VA / 4800 W | 192 VDC external | Rack, RS232/parallel/card |
| ET10KRS | 10000 VA / 8000 W | 192 VDC external | Rack |
5. LD48 discharge performance?
The LD48-50 is a 48 V 50 Ah LiFePO4 pack in a 2U case (440 × 432 × 88 mm, 28 kg), 57 V charge / 40 V cutoff, ~1600 cycles. Its BMS guards against over/under-voltage and short circuit. The LD48-50PRO (432 × 600 × 88 mm, 30 kg) adds a -20 °C to +60 °C working range and parallel capability.
6. Matching load and power factor?
Size in VA, then verify real watts. At 0.8 PF: 1000 VA ET1K → 800 W, 3000 VA ET3K → 2400 W, 10000 VA ET10KRS → 8000 W. Sum the load watts, add 20–30% headroom for inrush and growth, and never size purely by VA when the load is inductive or capacitive.