Can I see my balance without logging in with my seed?
The balance is not stored on the seed but on the addresses created from your seed.
So if you want to see your balance, you just need to know the addresses.
If your IOTA are spread across multiple addresses, in order to see your full balance you must have access to your seed, so it can retrieve every single address.
If you have a list of addresses your IOTA are stored in, you can input them into a site like the following: https://iotasear.ch/
Keep in mind that if your IOTA are stored across multiple addresses, each address will only show a portion of your total balance.