battery testing website?

You could try Orion in Switzerland. They have a lot of experience testing and matching rechargable cells for model car racing (1000-3600mAH range). I had a tour of their computerised and temperature stabilised facility some years ago.

..or you could try asking a company who make battery testers...

I guess it depends what you trying to do? Batteries can be quite difficult things to compare because there are a lot of variables - for example the total amount of energy you can extract from a battery can depend on...

a) When it was charged (Is it still warm? Has it self discharged?) b) How you charged it (fast, slow, pulse etc) c) How fast you extract the energy (fast enough to warm it up?) d) how you define full and empty.

If you are talking about Alkaline batteries - try the consumer group Which?

Colin