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Battery

Battery capacity

 

The total amount of electrical energy a battery can deliver. Because many batteries can be damaged if they are completely discharged, a battery’s capacity is usually higher than its usable capacity. Battery capacity is measured in kilowatt-hours (kWh), which shows how much total energy the battery can provide.

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LFP battery

 

The lithium iron phosphate battery (LiFePO4 or LFP battery) is a type of lithium-ion battery using lithium iron phosphate (LiFePO4) electrode as cathode and graphite electrode as anode. When the battery is discharging, the e-(electron) and Li+(Li-ion) will both move from the cathode to anode. And when the battery is charging, the process will be reversed. Because of the low cost, high safety, low toxicity, long cycle life, and other factors, LFP batteries are finding several roles in vehicle use, utility-scale stationary applications, and backup power.

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LFP VS NMC battery

 

Both NMC and LFP batteries are types of lithium-ion batteries. NMC batteries have a higher energy density, while LFP batteries last longer, and have better safety ratings. Recently, more and more companies have been manufacturing LFP batteries as opposed to NMC for home energy storage, mostly because LFP batteries are safer and more stable.

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Battery SOC/SOH/DOD

 

  • The State of Health (SOH) refers to the percentage of the battery's maximum capacity after aging and its original maximum battery capacity. It is defined as the ratio of the maximum battery charge to its rated capacity. Basket can hold 280 liters of water, 70% SOH means the bucket can only hold 196 (280 * 0.7) liters of Water.

  • SOC (State of Charge) SOC is the percentage of the battery's current remaining capacity and maximum available capacity. It is defined as the ratio of the remaining charge in the battery, divided by the maximum charge that can be delivered by the battery. For example: How much water is in the basket ? Full 100% ; Empty 0%.

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  • DOD (Depth of Discharge) refers to the discharge capacity of the battery. DOD is 100% if the battery support full discharge, discharge capacity can be up to 100%. DOD is 50% if the battery only discharges half of the electricity, discharge capacity can be up to 50%. The depth of discharge is estimated from the state of charge. In other words, SOC = 1 Minus DOD. 50% DOD means the bucket has held 50% water, remaining 50% space you canuse to hold water.​​

Battery C-rate

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The C rate of A battery cell represents the level of constant current charge or discharge that the cell can sustain for one hour of time. Table 1 illustrates the typical times at various C-rates. 1 C = 1 * rated capacity = 1 * 280 Ah = 280 A ; 1 C means this type of battery supports more than 1 hour of backup power.0.5 C = 0.5 * rated capacity = 0.5 * 280 Ah = 140 A; 0.5 C means this type of battery supports more than 2 hours of backup power. C-rate means the diameter of the water hole; 1 C means diameter of the water hole is 280; 0.5 C means diameter of the water hole is 140.​

Battery life cycles

 

1 cycle: means the battery has one time of fully charge and fully discharge

 

 

Throughput energy

 

Throughput Energy is the total amount of energy a battery can be expected to deliver over its lifetime

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