Traction Batteries
The real power behind an electrified vehicle is the traction or deep cycle battery. Usually lithium-ion, traction batteries are designed to provide power over a sustained period of time. This is in contrast to a Starting, Lighting and Ignition (SLI) battery, which provides a lot of power at once, and usually for a single or limited purpose like starting a car.
The size of the battery is what determines how far and how fast an electrified vehicle can go on electric power alone. It should come as no surprise that a BEV battery is larger than a PHEV battery -- up to 10 times -- which in turn can be up to 10 times larger than an HEV battery.
Another key factor is the flow of energy from the battery to the motor, and from recharging sources back to the battery. This is known as the charge / discharge cycle. Over time, the number of cycles a battery goes through will impact both battery life and vehicle performance.
A smaller, lighter HEV battery, for example, might charge / discharge several times on a short errand; and can go through 100,000 or more cycles in its lifetime.
A PHEV battery, with its greater EV speed and range, might go through a cycle once or twice a day, and up to 8,000 or more in its lifetime.
A BEV battery rarely sees a full charge / discharge except on longer journeys, and might see only 1,000 cycles in its lifetime.