NABCEP Energy Storage 2

Question 1

What is the primary purpose of a battery management system (BMS) in a lithium-ion energy storage system?

Accepted Answer

To monitor and protect individual cells from overcharge, over-discharge, and thermal events

Answer

A BMS monitors cell voltages, temperatures, and currents to protect lithium-ion cells from conditions that could cause damage or safety hazards.

Question 2

A battery bank has a usable capacity of 20 kWh and a maximum continuous discharge rate of 5 kW. What is the C-rate at the maximum discharge?

Accepted Answer

C/4

Answer

C-rate = discharge power / capacity = 5 kW / 20 kWh = 0.25C, which equals C/4.

Question 3

Which battery chemistry is most susceptible to thermal runaway and requires the most stringent safety controls?

Accepted Answer

Lithium nickel manganese cobalt oxide (NMC)

Answer

NMC lithium-ion batteries have higher energy density but are more prone to thermal runaway if overcharged, over-discharged, or physically damaged.

Question 4

In an AC-coupled energy storage system, where does the battery inverter connect?

Accepted Answer

On the AC bus, parallel with the solar inverter and loads

Answer

In AC-coupled systems, the battery inverter connects to the AC bus, allowing it to charge from both the solar inverter output and the grid.

Question 5

What does 'round-trip efficiency' measure in an energy storage system?

Accepted Answer

The ratio of energy delivered by the battery to energy required to charge it

Answer

Round-trip efficiency is the percentage of energy recovered from storage compared to the energy put in, accounting for losses in both charging and discharging.

(NABCEP) North American Board of Certified Energy Practitioners Solar Practice Test

(NABCEP) North American Board of Certified Energy Practitioners Solar Practice Test

NABCEP Energy Storage 2