Is there a limit to pet dragon level gain per battle?

[TinyMage]

I've been trying for a while to level my pet dragon from level 2 to over 20 in one battle so I could grab astral strike ( or whatever it's called ).

My hero is level 8 and my pet dragon starts the battle at level 2. I get a huge amount of experience ( like 60 ) per mana ball. Using some cheap tricks that involves sacrificing goblins I can put down like 50 mana balls in one battle. So after the battle I should get like 3000 experience right? Well apparently not, although the results screen does indeed say my pet dragon earned over 3000 experience it only gives me like 800, getting my pet dragon to about level 8-9.

So is there some kind of hard cap to dragon experience gain during battle and is there anything that I can do about it?