28 Chapter 3 Battery Terms Before we begin talking about battery design, we need to first understand some of the basic terminology surrounding the battery. Please note that this list is not intended to be an exhaus- tive list but rather is an explanation of some of the most common terms that you will find in the lithium-ion battery industry. For a more exhaustive list of terms and definitions, again I would refer the reader to one of the industry standards organizations such as the SAE stan- dard J1715 “Battery Terminology” (SAE International, 2014). Ampere—Often referred to as “Amp,” this is a unit of measurement of the battery current.
Anode—The anode is the negative “−” terminal inside the battery cell. It is typically a thin piece of highly conductive aluminum or copper that is coated with graphite, carbon, or other similarly conductive material. Battery Management System (BMS)—The BMS is the control system within the battery pack that consists of one or more electronic controllers, which manages the charging and discharging, monitors the temperature and voltage, communicates with the vehicle system, balances the cells, and manages the safety functionality of the battery pack. Beginning of Life (BOL)—The term BOL refers to the battery energy, capacity, and power when it is first built or is at the beginning of its life.
C-rate—The term C-rate is important; it refers to the rate at which a battery can charge or discharge all of its energy (or power). In other words, it describes how fast a battery can accept a charge or give up its power (discharge). C-rate is described in relation to a 1 h discharge, so 1C-rate is equal to the rate at which a battery is fully discharged (or charged) in 1 h. Along the same lines, 2C-rate would then be equal to the rate at which a battery is fully discharged in 30 min (60 min/2C = 30 min). If the C-rate number goes up the discharge time goes down, and vice versa. So 0.5C discharge rate would be equal to a 2 h discharge period (60 min/0.5C = 120 min or 2 h).
Capacity—Capacity is measured in Ampere hours (Ah) and is a measure of amount of energy in a system. Think of capacity as being analogous to the size of the hose that water may flow through. Larger capacity is equal to a larger hose. CARB—The CARB is a legislative group in California with the mandate of passing legislation that will improve the air quality of the state. CARB is often also referred to “ARB” for the Air Resource Board. Cathode—The cathode is the opposite of the anode; it is the positive “+” terminal inside the battery cell.
It is typically a thin piece of aluminum or copper that is coated with lithium-ion chemistry such as lithium-iron phosphate (LFP), lithium cobalt oxide (LCO), lithium-nickel/manganese/cobalt (NMC), lithium-manganese oxide (LMO), or other lithium-based chemistry.