Battery For Psion Revo How Do I No That Which Battery I Am Using For My Laptop?

How do I no that which battery I am using for my laptop? - battery for psion revo

I have a problem with my laptop battery can not be modified, if the load is disconnected. It takes only 15 to 20 minutes. I thought I could get a new one. Who knows how to find the correct name of the stack on my laptop. This allows you to eBay by looking at them.