For those of you who use the battery pack with your Medela PISA, is the suction as good as when you use the wall charger? Also, have you ever had batteries explode while using it?

I'm travelling right now in Europe so I brought along the battery pack and I found that the suction is terrible and I just heard a loud pop which I'm fairly certain is a battery exploding...

I put in fresh batteries before my trip and I noticed the suction issue right away and the exploding problem after 35 minutes of pumping (over 2 sessions).