mW (80–100 mA). Standby current is much lower, less than 0.2 mA for one 2006 microSD card. If there is data transfer for significant periods, battery life may be reduced noticeably; for reference, the capacity of smartphone batteries is typically around 6 Wh (Samsung Galaxy S2: 1650 mAh @ 3.7 V). Modern UHS-II cards can consume up to 2.88 W, if the host device supports bus speed mode SDR104 or UHS-II. Minimum power consumption in the case of a UHS-II host is 720 mW. Storage capacity and compatibilities All SD cards let the host device determine how much information the card can hold, and the specification of each SD family gives the host device a guarantee of the maximum capacity a compliant card reports. By the time the version 2.0 (SDHC) specification was completed in June 2006, vendors had already devised 2 GB and 4 GB SD cards, either as specified in Version 1.01, or by creatively reading Version 1.00. The resulting cards do not work correctly in some host devices. SDSC cards above 1 GB A host device can ask any inserted SD card for its 128-bit identification string (the Card-Specific Data or CSD). In standard-capacity cards (SDSC), 12 bits identify the number of memory clusters (ranging from 1 to 4,096) and 3 bits identify the number of blocks per cluster (which decode to 4, 8, 16, 32, 64, 128, 256, or 512 blocks per cluster). The host device multiplies these figures (as shown in the following section) with the number of bytes per block to determine the card's capacity in bytes. SD version 1.00 assumed 512 bytes per block. This permitted SDSC cards up to 4,096 × 512 × 512 B = 1 GB, for which there are no known incompatibilities. Version 1.01 let an SDSC card use a 4-bit field to indicate 1,024 or 2,048 bytes per block instead. Doing so enabled cards with 2 GB and 4 GB capacity, such as the Transcend 4 GB SD card and the Memorette 4 GB SD card. Early SDSC host devices that assume 512-byte blocks therefore do not fully support the insertion of 2 GB or 4 GB cards. In some cases, the host device can read data that happens to reside in the first 1 GB of the card. If the assumption is made in the driver software, success may be version-dependent. In addition, any host device might