It can get maximum storage capacity with 2 microSDHC or 2 microSD cards. CR-5400 converts 2 microSD(HC) cards into one MS Pro Duo stick. You can get twice the capacity at a lower price. The card types can be mixed too.
This adapter can work with only one microSDHC card as well. The second slot can be equipped anytime later.
Kingston 32GB Class 4 MicroSD Memory Card w/ FREE SDHC Adapter
SDHC cards offer larger volume data storage and optimized recording performance with support for FAT 32 file formats. In addition, Kingston's SDHC cards use new speed class ratings known as Class 2, 4 and 6 that deliver a minimum data transfer rate for optimum performance with SDHC devices.
Although identical in size to todays standard SD card, the new SDHC cards are designed differently and are only recognized by SDHC host devices. To ensure compatibility, look for the SDHC logo on cards and host devices (cameras, camcorders, etc.).
For added reliability and durability, Kingston's solid-state SDHC memory cards are built of nonvolatile memory components and have no moving parts that could wear out or break. All cards are 100-percent tested by the manufacturer.
Please check compatibility before you purchase.
For Lithium battery expansion board:
Battery capacity: 3800mAh
Maximum output current: 1.8A
Output voltage: 5.1V ± 0.1V
Standard charging current / voltage: 1.2A/5.0V
It's convenient to power on / off raspberry pi via battery swith;
It can last about 9 hours if only pi 3.
The Lithium battery expansion board can be also used on cellphone.
Note: You can still charge this battery even if the switch is turn off;