My first year lease, I gave a security deposit of 475,which is equal to 1 months rent. I am signing on for a second year. Can my landlord charge me a 475 security deposit again?

They still have your original security deposit, ( that was not used for rent or should not have been)

Now if they wish to make the deposit 950 they could ask for additional.

But in general no, there is no additional deposit to renew a lease.

If your rent is raised, they can generally ask for an increase in the security to cover the difference, but not for another full month's worth.