Victron energy Venus GX Manual page 59

The transmission of the data logs has been designed to work also on bad internet connections. Lines
of up to 70% permenant packet loss are still sufficient to get the data out, even if delayed in some
cases.
Adding an external storage device
When unable to transmit the logs, then the GX device will store them to non-volatile storage (ie. data
is not lost on a power loss or reboot).
The GX device can store 48 hours worth of logs internally. To extend this period, insert a microSD
card or USB stick. You can see the internal storage status in the settings.
Note that, when inserting such storage device, any internally stored logs will automatically be
transferred to the inserted stick: no data is lost.
With or without an external storage device inserted, the GX Device will always keep trying to connect
to the portal and transmit all backlogged logs. That means that even with months worth of backlog,
once it re-acquires an Internet connection, all of the backlog is sent out. The data is sent in a
compressed manner: sending a lot of backlogged data will use considerably less bandwidth than than
sending the data with a continuously available internet connection.
Storage device requirements
MicroSD cards or USB flash drives must be formatted as FAT12, FAT16 or FAT32 file systems -
and not exFAT or NTFS.
SD and SDHC type microSD cards of 32 GB capacity and smaller are sold containing FAT12,
FAT16 or FAT32. They can be used without a problem, unless they are subsequently re-
formatted to a different file system.