There are huge differences in capacity, cost and conditions of application between 100Ah, 200Ah and 300Ah lifepo4 batteries (lithium iron phosphate batteries). For example, in the 12.8V system, the capacity of a 100Ah battery is 1.28kWh, of a 200Ah battery is 2.56kWh, and of a 300Ah battery is 3.84kWh. For every increase of 100Ah capacity, the battery life is increased by about 80% (assuming a 500W load power, a 100Ah battery would last 2 hours, and a 200Ah battery would last 4 hours). The 300Ah lasts 6.1 hours. For instance, when a particular RV user operates a 300Ah battery to power the air conditioner (1.5kW), the running time is increased from 1.7 hours with a 200Ah battery to 2.6 hours (an increase of 53%).
Price and Volume:
100Ah: Market price around ¥2500, volume 0.04m³, weight 12kg.
200Ah: Price ¥4500 (80% more than 100Ah), volume 0.06m³ (+50%), weight 24kg (+100%).
300Ah: ¥6,500 (160% increase from 100Ah), 0.09m³ (+125%), 36kg (+200%).
The unit energy cost is ¥1953 (100Ah), ¥1758 (200Ah), and ¥1693 (300Ah) respectively.
The unit energy cost reduces as the capacity rises.
Load and efficiency applicable:
100Ah: Suitable for low-power use (≤1kW), such as lighting (200W) and routers (50W), it can meet the power supply needs of users with a daily average power consumption of 3kWh at night (discharge depth 80%).
200Ah: Can charge medium-power appliances (e.g., 1.5kW air conditioner +500W refrigerator), and when combined with a 3kW inverter, peak efficiency is 95% (92% for 100Ah).
300Ah: In instances of high power demands (over 3kW), a certain off-grid house uses a 300Ah battery to drive a water pump (2.2kW) and an electric stove (3kW), and for one cycle power consumption of 5kWh (depth of discharge 65%), and an average of 0.8 cycles per day.
Cycle life and cost-effectiveness
The total energy output differs considerably although all three batteries will provide 3,500 cycles at 80% depth of discharge.
100Ah: 1.28kWh × 3500 cycles = 4.48MWh, cost per kilowatt-hour ¥0.56 (¥2500 ÷ 4.48MWh).
300Ah: 3.84kWh × 3500 cycles = 13.44MWh, cost per kilowatt-hour is ¥0.48 (¥6500 ÷ 13.44MWh), and this is 14% cheaper than 100Ah.
If a user consumes an average of 5kWh a day, the electricity cost of a 300Ah battery for 10 years is ¥4,200 lower than that of a 100Ah battery (at ¥1.2/kWh).
Charging time and compatibility:
100Ah: It can be charged from 0% to 100% in 2 hours using a 50A charger.
300Ah: It would require a 100A charger to charge at the same pace. Charging it with just 50A charger would take 6 hours.
A solar energy user measured that when a 200Ah battery is charged through a 20A MPPT controller and exposed to sunlight for an average of 5 hours per day, 100Ah (50% of the capacity) can be replenished, while a 300Ah battery requires 7.5 hours (or upgraded to a 30A controller).
Application scenario comparison:
Rv living: A 200Ah battery can meet the needs of a refrigerator (1kWh per day) and an air conditioner (2 hours), and is 33% lighter than a 300Ah battery, so is more suitable for small cars.
Off-grid energy storage: A 300Ah battery and a 5kW photovoltaic system will store 76% of the daily power generation (assuming 15kWh average daily power generation), reducing the frequency of use of the diesel generator (annual fuel saving of ¥5000).
Emergency backup: With good cost performance, the 100Ah battery can power vital equipment (such as 500W medical devices) for 2.5 hours. Upfront investment is 62% lower than that of the 300Ah battery.
Conclusion: The lifepo4 battery capacity must be selected on a trade-off between energy consumption, space and cost. The 100Ah is appropriate for low-load short-term application, the 200Ah is balanced, and the 300Ah is targeted at high-energy-consuming long-term applications, with a lower cost of full life cycle.