Hybrid Electric Vehicles, 2nd Edition

8Diagnostics, Prognostics, Reliability, EMC, and Other Topics Related to HEVs

8.1 Diagnostics and Prognostics in HEVs and EVs

Any vehicle, whether conventional, hybrid, or pure electric, ought to have some sort of diagnostics (find the cause of a problem that has “already happened” to the vehicle) and prognostics (find problems which “will or could possibly happen” in the future), given the present condition of the vehicle based on monitoring of various information within the vehicle. With this in mind, all modern automobiles have onboard diagnostic functions that can give a certain amount of diagnostics, but not prognostics. Diagnostics can be at several levels. One is at the vehicle level within the vehicle itself; this can inform the driver or basic level service personnel about what might have happened. The second level can be at somewhat deeper maintenance level when the vehicle can be dismantled at different subsystem levels in a repair shop, the problem pinpointed, and the item concerned replaced. The third level can be at the automotive dealer or eventually the vehicle manufacturer level to find out why a subsystem failed. Finally, the diagnostics can be at the subcomponent level or component manufacturer level when more microscopic analysis of the component can be initiated to find design or other flaws, if any. Up to the second level, that is, the maintenance level, the correctional step normally is replacement/repair of a part or subsystem, without necessarily trying ...