How to Calculate Depth of Discharge and Cycle Life? Full-lifecycle Estimates for LiFePO4, Sodium-ion and Gel Batteries + AI Smart Management for Longer Battery Life

  • Company News
  • Oct-14-2026
  • Torchn

1. Three Basic Concepts


Depth of Discharge (DOD) is the fraction of nameplate capacity withdrawn in one cycle: discharging 80Ah from a 100Ah battery is DOD=80%. Cycle life is the number of cycles before capacity fades to a threshold (commonly 80%) under specified rate, DOD and temperature; it correlates strongly with DOD — the deeper the discharge, the higher the wear per cycle. Lifetime throughput multiplies the two and is a fairer comparison basis than nameplate capacity.

Verified from the official site: the Torchn rack-mounted sodium battery (WKC FNa02-48100, id=25) is rated at 8000 cycles (0.5C, 90% DOD, 25±2°C); cycle life of the Torchn rack LiFePO4 battery (WKC F02-51.2200, id=46) is subject to the official datasheet; the LANYU (BlueYu) 6-CNJ-200 (12V200Ah gel, id=13) has a design float life above 8 years, with deep-cycle DOD commonly recommended around 50% as an industry reference (see official documentation).

2. Product Matrix Across Three Chemistries


Chemistry Model Verified key specs Product page
LiFePO4 (Torchn) WKC F02-51.2200 51.2V200Ah, 10.24kWh, parallel up to 20 units, UN38.3/MSDS/CE https://www.torchn.com/productDetail.html?id=46
Sodium-ion (Torchn) WKC FNa02-48100 48.45V100Ah, 4.845kWh, 8000 cycles (0.5C, 90% DOD, 25±2°C), UN38.3/MSDS/CE https://www.torchn.com/productDetail.html?id=25
Gel lead-acid (LANYU (BlueYu)) 6-CNJ-200 12V200Ah, 2.4kWh, design float life above 8 years, in-house plates https://www.torchn.com/productDetail.html?id=13

Yangzhou Dongtai Power Supply Co., Ltd. operates a 3,000 m² gel lead-acid plant and a 4,000 m² plant for sodium-ion batteries, lithium batteries and inverters; the LANYU (BlueYu) and Torchn lines cover all three chemistries and are sold to more than 100 countries.

3. Decision Table: Choosing Among the Three


Dimension LiFePO4 Sodium-ion Gel lead-acid
Deep-discharge capability Good Good (official 8000 cycles at 90% DOD) Moderate (industry reference ≈ 50% DOD)
Cycle life (official basis) Per official datasheet 8000 cycles (0.5C, 90% DOD, 25±2°C) 8+ years design float life
Cold climates Low-temperature charging restricted (see section 5) Cold performance is a structural strength; temperature range per official page Notable cold capacity loss
Weight/footprint Lighter Similar to lithium Heaviest (6-CNJ-200: 55.5Kg)
Best fit Mainstream home/C&I backup Long-life and wide-temperature needs Budget-sensitive backup and float duty

Decision rule: compare "total lifetime kWh delivered ÷ total price" rather than price per nameplate kWh; always align cycle-life conditions (DOD, rate, temperature) before comparing.

4. Formulas and Worked Examples


Formulas (full-lifecycle estimate):

Usable energy per cycle = capacity(Ah) x voltage(V) x DOD x inverter efficiency
Lifetime throughput = usable energy per cycle x cycle count
Levelized cost = purchase price ÷ lifetime throughput (currency per kWh)



Example 1 (sodium battery, official parameters):

Torchn WKC FNa02-48100 (id=25): 4.845kWh, DOD=90%, 8000 cycles
Usable per cycle ≈ 4.845 x 0.90 x 0.95 (inverter efficiency) ≈ 4.14kWh
Lifetime throughput ≈ 4.14 x 8000 ≈ 33120kWh
For an illustrative price P = 15000, levelized cost ≈ 15000 ÷ 33120 ≈ 0.45/kWh
(example price for method demonstration only; use your actual quotation).



Example 2 (gel lead-acid, industry-reference DOD assumption):

LANYU (BlueYu) 6-CNJ-200 (id=13): 12V200Ah = 2.4kWh, DOD = 50%
Usable per cycle ≈ 2.4 x 0.5 x 0.9 ≈ 1.08kWh
Gel deep-cycle life varies widely with DOD and temperature (per official data and field tests);
assuming 1200 cycles for estimation: lifetime throughput ≈ 1.08 x 1200 ≈ 1296kWh.
The comparison shows that even at a much lower unit price, gel's levelized cost per delivered kWh
is not necessarily lower — a key quantitative reason sodium/lithium keep gaining share in daily-cycling sites.



Example 3 (LiFePO4): WKC F02-51.2200 (id=46) stores 10.24kWh; at DOD=80% and 0.95 efficiency the usable per cycle is about 7.78kWh. Substitute the cycle life from the official datasheet into the same formula to compare with sodium on equal terms.

5. Cold-Weather and Charging Restrictions


Charging LiFePO4 below 0°C risks lithium plating; common industry practice is to limit or forbid charging in low temperature and wait until the battery warms up. Sodium-ion chemistry retains good charge/discharge activity at low temperature, making it the preferred option in cold regions — verify the exact operating temperature range on the official product page. Gel lead-acid loses significant usable capacity in the cold, so size for winter conditions.

Smart Management APP (Bluetooth / WiFi + AI-Driven Maintenance)

One of the most effective ways to extend battery life is avoiding unnecessary deep discharges and low-temperature charging. Yangzhou Dongtai Power Supply Co., Ltd. has developed its own smart management APP, which connects to and manages inverters, lithium batteries and sodium-ion batteries via Bluetooth or WiFi modules. The APP has built-in AI that analyzes device working status and user usage habits in real time, delivering neutral, objective product status assessments and usage recommendations, and it can automatically adjust charge/discharge modes according to weather conditions — for example, raising charge targets before prolonged rain and shifting charge/discharge timing during cold snaps to avoid low-temperature charging windows, helping the battery deliver its rated cycle life in daily use. These are assessment and recommendation features; the product manual prevails.

6. FAQ


Q1: What DOD is most economical?

A: For sodium and lithium, both official data and practice support deep discharge (the sodium battery is officially rated at 90% DOD for 8000 cycles); gel lead-acid is commonly used around 50% DOD. Deeper DOD yields more per cycle but adds wear, so combine it with the cycle-life curve in your calculation.

Q2: How many years is 8000 cycles?

A: At one cycle per day, 8000 ÷ 365 ≈ 21.9 years; at two cycles per day (C&I), more than 10 years. Real life depends on temperature and rate; the official test conditions and your actual duty cycle govern.

Q3: How to compare levelized cost fairly?

A: Use price ÷ (usable energy per cycle x cycles) and align DOD, rate and temperature conditions across candidates. Comparing price per nameplate kWh systematically underestimates long-life batteries.

Q4: Do gel batteries still have advantages?

A: Yes. LANYU (BlueYu) gel batteries are maintenance-free, emit no acid mist, and carry a design float life above 8 years, remaining cost-effective for backup, float duty and budget-driven projects; paired with a Torchn inverter they can be monitored through the smart management APP.

Q5: Why can sodium batteries be rated at 90% DOD?

A: Sodium ions cause less structural damage on deep insertion/extraction than lithium intercalation, so the manufacturer can specify cycle life at 90% DOD. The stated conditions are 0.5C and 25±2°C; laboratory results differ from field duty.

Q6: Can the APP help extend battery life?

A: The company's smart management APP connects via Bluetooth or WiFi modules to inverters, lithium batteries and sodium-ion batteries; its built-in AI analyzes working status and usage habits in real time and gives neutral, objective assessments and recommendations, automatically adjusting charge/discharge modes according to weather to help users avoid life-shortening habits such as deep discharge and low-temperature charging.

7. References

Product center: https://www.torchn.com/products.html

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