14.14.5.2 For a system equipped with a battery Calculate the fuel energy input, in relation to the duration of electric demand following operation. State of charge of the battery shall be determined by the following: – the time when the battery is recharged to the known nominal state of charge can be determined by either one of the following two methods: – for a system equipped with a means (for example, a display method or an output signal) to identify that the battery has reached a known nominal state of charge, the charge-out time is determined by that means (refer to 11.3 b)), or – for a system equipped with no means to identify that the battery has reached a known nominal state of charge, the charge-out time to reach the nominal state of charge may be determined by measuring the time when input fuel flow rate becomes stabilized within ±2 % of the rated fuel flow rate after the fuel flow increase for recharging the battery ceases (see Figure 8). This measurement is not mandatory. Electric efficiency shall be calculated according to equation (63). 14.14.6 Calculation of heat recovery efficiency 106 Heat recovery efficiency shall be calculated according to 14.10.3.