Hi Biff,
Thank you for contacting the MPS Forum. We really don’t have a lot of charging devices capable of handling 40V input. I would say the max we can do right now is 36V with the MP2759. I’m not sure what you mean by connecting the battery to the USB-C input, can you explain the difference of that from using the USB-C input to power a battery? I think that anything with power path management could potentially achieve this if I am interpreting things correctly. Please let me know and I will do my best to help you out, but at 40V input you will either need to use a 2 stage solution or try to use 36V max for the MP2759.
Thanks,
Brendan Schoemehl
Field Applications Engineer
Monolithic Power Systems | MPS Now