Abstract
To give full play to battery capability, the state of power (SoP) should be predicted in real time to inform the vehicle control unit (VCU) whether the upcoming driving scenarios of acceleration overtaking, ramp climbing, constant cruising and feedback braking can be sustained. In general, battery SoP conforms to prescribed constraints on voltage, current, and state of charge (SoC). Specifically, this paper takes the generally ignored operating temperature into consideration based on a differential temperature-changing model. Consequently, a SoP prediction method restricted by both electrical and thermal constraints was obtained. Experimental verifications on a Li-ion battery pack suggest that the proposed SoP prediction method can provide favorable reliability and rationality against diverse time durations, temperatures, and aging states in comparison with the instantaneous power obtained using the hybrid power pulse characteristic (HPPC) method.
Highlights
Li-ion batteries are becoming the choice for all kinds of portable electronics and electric vehicles (EVs) due to the high energy density [1,2]
Since a considerable proportion of EVs are installed with an energy regeneration subsystem, the endurance mileage is concerned with the charging power capability in the case of regenerative braking
The above sections give equivalent circuit model (ECM) parameters and the state of charge (SoC); the state of power (SoP) is predictable according to the prescribed constraints concerning terminal voltage, affordable current, preferable SoC, and temperature ranges
Summary
Li-ion batteries are becoming the choice for all kinds of portable electronics and electric vehicles (EVs) due to the high energy density [1,2]. Battery SoP is crucial information that determines the allowable demand of the powertrain [4], for example, the maximum discharging power for propelling and the strongest charging power for energy recovery [5,6]. The following mechanism defects of the conventional PNGV-HPPC method make it inapplicable for engineering practice: the used battery model is too simple to manage transient behavior with enough details; the sole constraint of voltage cannot achieve full protection for the battery because certain other restrictions, for example, maximum temperature, are not reflected; and instantaneous power without an explicit consideration of time horizon, which usually gives optimistic results, is unsuitable for real driving scenarios [8]. A battery SoP is predicted involving diverse constraints on affordable terminal voltage and current, and recommended SoC and temperature ranges.
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