I have been running 5S Zippy packs for ages & had no issues, apart from the usual MM related issues in the beginning which we all had. Since then, no probs at all with ESC, but, I have killed 3 of my 5 packs.
I've gone back to 2 x 2s 5000mAh 40C packs to make a 4S. Works awesomely!!
Can you say wheelies on command with a truggy?
Losi SCTE SC4 Pro 4000kv, Tekin RX8, 2S
MP7.5 Kanai III Tekno Neu 1515/2.5D 1700kv MM 4S
LST 2 Carbon CC 1717 1Y 1580kv MM 6S
Futaba 3PKS Spektrum Pro