Hi All,
I've made a datalogger module with an arduino nano, accelerometer and SD card module. This setup is powered by a single LiPo cell hooked up through a 5V boost convertor to the Vin. So far so good and everything works.
Now I want to modify it, which will involve using the USB connector on the board. I have removed the battery, but the boost convertor is still attached; could this cause problems? (the circuit on the battery side will be open, whereas the nano side will receive 5v from the board) Thanks for any help 
Regards,
Lorenzo
Everything is wrong about your description.
For a start, you refer to connecting the 5 V boost converter to Vin rather than the 5 V terminal.
But the general design is wrong. For a datalogger, you use a 3.3 V Pro Mini directly connected to the battery. The SD card already runs at 3.3 V in any case. You connect a USB-serial adapter to download data but feeding the 5 V through the regulator in this case so that the SD card still gets 3.3 V.
It may well be wrong in the sense that it could be done better, but it does do the job it's meant to do so in that regard it's fine. It's my first project though so thanks for the tips.
I did attach the boost converter to the Vin to also use the onboard regulator (as the specs read something like 'ONLY CONNECT REGULATED 5V TO THE 5V PIN and I wasnt sure if my cheap booster would regulate it properly or to the exact right level). Also my accelerometer runs at 5V and the SD card module I have can also take 5V. I get that all the up-and-down regulating is hardly efficient but that doenst really matter as the smallest battery I could find (240mah lipo) can still power it an order of magnitude longer than is required.
Apologies if I'm butchering elegance here 