Issue link: https://resources.mouser.com/i/1437660
LT8301/LT8302 Isolated Flyback Converters 42VIN Micropower No-Opto Isolated Flyback Converter with 65V/3.6A Switch 3.6A, 65V Internal DMOS Power Switch No Transformer Third Winding or Opto-Isolator Required for Output Voltage Regulation ADuM7701 16-Bit, Isolated Sigma-Delta Modulators Isolated Sigma-Delta Modulator 16 bits, no missing codes 5MHz to 21MHz master clock input frequency LEARN MORE LEARN MORE 25 Saving Power for the Future | ADI Li-ion cells SOC and SOH estimation, it was omitted since it is based on external measurements utilizing instrumentation. The methods based on the electrolytes' physical properties and artificial neural networks are not applicable for Li-ion batteries. Technical Principle (For a more detailed description and equations, refer to the full article on A Closer Look at SOC\SOH Estimation Techniques.) The releasable capacity (C releasable ) of an operating battery is the released capacity when it gets completely discharged. Accordingly, the SOC is defined as the percentage of the releasable capacity relative to the battery rated capacity (C rated ), given by the manufacturer. A fully charged battery has the maximal releasable capacity (C max ), which can be different from the rated capacity. In general, C max is, to some extent, different from C rated for a newly used battery and will decline with the used time. It can get utilized for evaluating the SOH of a battery. When a battery is discharging, the depth of discharge (DOD) can get expressed as the percentage of the capacity that has gotten discharged relative to C rated , Where C released is the capacity discharged by any amount of current. With a measured charging and discharging current (Ib), the difference of the DOD in an operating period (Ʈ) can be calculated by where I b is positive for charging and negative for discharging. As time elapsed, the DOD is accumulated To improve the accuracy of estimation, the operating efficiency denoted as ŋ is considered and the DOD expression becomes, With ŋ equal to ŋc during the charging stage and equal to ŋd during the discharging stage. Without considering the operating efficiency and the battery aging, the SOC can get expressed as Considering the SOH, the SOC is estimated as The estimation process is based on monitoring the battery voltage (Vb) and I b . The battery operation mode can be known from the amount and the direction of the operating current. The DOD is adding up the drained charge in the discharging mode and counting down with the accumulated charge into the battery for the charging mode. After correction with the charging and discharging efficiency, a more accurate estimation can get realized. The SOC can then get estimated by subtracting the DOD quantity from the SOH one. When the battery is open-circuited with zero current, the SOC is directly obtained from the relationship between the OCV and SOC. Note that the SOH can get reevaluated when the battery is either exhausted or fully charged, and manufacturers specify the battery operating current and voltage. The battery may be considered drained when the loaded voltage (V b ) becomes less than the lower limit (V min ) during the discharging. In this case, the battery can no longer be used and should get recharged. At the same time, a recalibration to the SOH can get made by reevaluating the SOH value by the accumulative DOD at the exhausted state. On the other hand, the used battery may be considered fully charged if (V b ) reaches the upper limit (V max ), and (I b ) declines to the lower limit (I min ) during charging. A new SOH is obtained by accumulating the sum of the total charge put into the battery and is then equal to SOC. In practice, the fully charged and exhausted states occur occasionally. The accuracy of the SOH evaluation can be improved when the battery is frequently fully charged and discharged. Thanks to the simple calculation and the uncomplicated hardware requirements, the enhanced coulomb counting algorithm can be easily implemented in all portable devices, as well as electric vehicles. Also, the estimation error can be reduced to one percent (1%) at the operating cycle next to the reevaluation of the SOH.