New methodology to on-site estimate the state of health of batteries for elevator applications

Abstract

This paper presents a new method to determine the state of

health or SOH of one or more batteries supplying an elevator.

The proposed method permits an accurate estimation of the

state of health or SOH of at least one single battery, without

the need of extra elements in the regular architecture of an

elevator, because some existing elements are used for this

purpose. In order to achieve this objective, a partial discharge

of the energy storage system is forced through the braking

resistor of the elevator if the SOH of the battery has to be

estimated, with a duty cycle less than a 100%, because the

braking resistor is limited in its working temperature and it is

not designed for continuous discharging. In the aforementioned

discharging process the battery voltage, the current delivered

by the battery to the braking resistor and the number of pulses

done during the test are measured. Taking into account these

measurements during the pulsed discharge an approximation of

the available capacity within the battery is obtained. A previous

characterization of the energy storage system in the laboratory

permits to know the amount of pulses that the energy storage

system under test has to supply in order to be considered

suitable to continue operating the elevator. Thus, evaluating

the amount of pulses given by the battery in situ in the real

application and comparing it with the required minimum

value obtained in the characterization in the laboratory, the

SOH value of the energy storage system is estimated. This

paper presents the whole methodology followed to reach this

estimation.