I've got a registered Oyster card with an online account. I've got
another one that's not been used for a while but has been registered -
but although i thought I had the login it doesn't work. Requesting
username and password just gives me details for my main card as all it
asks for is email and postcode or username and postcode. There seems to
be no way of getting details for the other Oyster card as the number is
not used to retrieve details - is that correct?

All I want to do is top it up and give it to my son.

E.