What this means is you have to have gotten at least 1500HP of damage done to your tank by any means during a battle including death and drowning, and be able to repair the tank when it returns to the garage. I'm not sure what happens if you don't have the silver to repair it as that never happened to me, but I'm assuming it would still pop if you earned the silver needed then repaired it?
I used a Tier 9 British medium tank. I discovered however that there are a number of Tier 8 heavy tanks that have at least 1500 HP, so you don't need a Tier 9 or 10. I wasn't able to find any Tier 7 tanks with 1500 HP, although the Black Prince comes close with 1450 HP.
To view the hit points for any tank, go to the tank tree, then press
when looking at any tank. This is the only way I've found to see the hit points as if you view tank details from the garage or the packages screens it only shows you other information.
Generally, NO Artillery of any Tier will have even close to 1500 HP, Tank Destroyers are the next weakest, then it goes Light Tanks, Medium Tanks, and Heavy Tanks usually. No surprise, Heavy tanks live up to their billing with their armor and hit points outclassing all the other types.
I went for this achievement:
before the French and Chinese tank lines were released. I ended up going for a Tier 10 that required over 1 million XP!
Now, with the French and Chinese tank trees released, it's worth combining the tier 10 achievement with the 1500HP repair and this one:
If going the way of the cheapest Tier 10, you'll want to go French tech tree for a total of 745,850 XP to the French Tier 10 Medium tank.
If you go the Chinese pathway, it'll take 158,240 XP to get the Chinese Light/Medium/Heavy achievement at Tier 7, and then another 679,900 XP to reach Tier 10.
Either pathway you go, once you reach Tier 9 you'll be able to get the 1500 HP achievement.
Either pathway is SO much faster than the tank tree I chose for my Tier 10--the British Medium/Light tree.
(NOTE: My XP totals may be on the high side, because sometimes when researching packages, the next packages in line reduce greatly in XP cost)