BMS Diagnostics Maintenance & Safety Standards 2

Question 1

Which diagnostic parameter best indicates the beginning of lithium plating in a Li-ion cell during charging?

Accepted Answer

Coulombic efficiency dropping below 99.5%

Answer

Coulombic efficiency (charge-out/charge-in) dropping below ~99.5% is an early indicator of lithium plating, as plated lithium is not fully recovered on discharge.

Question 2

A BMS reports a persistent cell voltage divergence that increases during discharge but resets after a rest period. The most likely cause is:

Accepted Answer

Cell-to-cell capacity imbalance

Answer

Capacity imbalance causes weaker cells to deplete faster under load, creating divergence that recovers at rest as OCV equalizes.

Question 3

When performing insulation resistance testing on a high-voltage battery pack, what minimum acceptable IR value is typically required per IEC 60664?

Accepted Answer

1,000 Ω/V

Answer

IEC 60664 and most EV safety standards require a minimum insulation resistance of 1,000 Ω/V (100 Ω/V for AC systems) relative to system voltage.

Question 4

A technician uses an EIS (Electrochemical Impedance Spectroscopy) tool and finds the Warburg impedance component has significantly increased. This most likely indicates:

Accepted Answer

Electrolyte depletion or lithium-ion diffusion limitation

Answer

The Warburg element in an EIS Nyquist plot represents solid-state diffusion; a large Warburg tail indicates slowed Li-ion transport due to electrolyte depletion or concentration polarization.

Question 5

OSHA 1910.303 requires that electrical equipment in battery rooms must be listed and labeled. What is the primary purpose of this requirement?

Accepted Answer

To confirm equipment has been evaluated for safety by a recognized testing laboratory

Answer

OSHA requires listing/labeling to confirm that a Nationally Recognized Testing Laboratory (NRTL) has evaluated the equipment for electrical safety hazards.

(BMS) Battery Management System Certification Practice Test

(BMS) Battery Management System Certification Practice Test

BMS Diagnostics Maintenance & Safety Standards 2