Ok. Thanks guys. Even though I got them for free, I don't want to destroy them. I guess I am going to have to find some other batteries.
Hey Free is Free
Since these are startup batteries, YOU can still use them. Just know that they should be used to learn and emergencies ONLY.
Are they in fairly good working order?
What do you intend to use them for?
The best thing you can do to lengthen their life is to make sure you do not draw more than 20% of their usable Ahr.
These are heavy-duty style batteries (Truck /Bus types).
I would hazard a guess that this large heavy battery will give you about 100Ahrs MAX, so 20% that would be usable which you should return post-haste
BUT the better thing to do would be to get in touch with Interstate and ask them the total Ahr rating of these.
I'm sure an email or phone call would get you the answer in quick order.