! !! !!!! Awesome-I thought this was impossible! I'm going to hook up several 9v like that!

In the swiss army we used crappy zinc carbon ones as hand-warmers in the winter. :)
Never exploded nor leaked...

But high-current ones like alkanine or rechargeables (Hell: Litium! If i think about that, it gives me shivers) are a bad idea because the pressure-build-up may actually blow it...

and btw dont do it with non alkaline or zinc carbon batteries. other types can explode. rechargeables are very likely to explode

i dont think connecting them like this would work, it would have to be a closed circuit for heat to build up. take 2 and connect the pos to neg on both

Actually, yes this does work. When I was younger, someone in my school did this. The batts defenently exploded, and there was a battery acid on the walls and there was a loud crack. I believe the batts have to be fresh though

I remember when I was really little I did this with two batteries. I then held them up and tried to "charge" the one on the bottom by letting the energy flow into it. Thank god they were both dead ;-)

. No. You've created a 45V battery. Measure the voltage between the two open terminal and see. . If you mean connecting the terminals of just two "transistor" batteries, they will discharge quickly and may get hot (leading to swelling), but shouldn't explode.

you can still blow a battery up this way. These guys hooked up like over a hundred 9 volt batteries and drew arcs from the terminals, but then one of the batteries exploded! See it on youtube

if the internal resistance of one battery is higher it'll get more power than it's fair share in the short circuit

with this higher power it'll heat even more and maybe enough to explode

seems unlikely in 2 battery setup but possible with more batteries