The battery in one of my vehicles froze overnight, sides are bowed out slightly, but the casing doesn't appear to be cracked. Once it thaws out (assuming it hasn't cracked) is it still ok to use, or should I be getting a new battery?

I think the battery must be discharged to be able to freeze.
WHATEVER you do don't try to jump it or charge it until it completely thaws out. It can explode.

A good battery will not freeze.............even at -40. So, if yours froze, it was discharged and probably won't hold a charge anymore. If the sides bulged, it is serious. I've had batteries that had just a few ice crystals in a cell or two, and even those couldn't be saved.
Junk it before it gives you anymore problems. It will never work in cold weather again.

If you need it to get going somewhere- pull it, let it thaw- then check the electrolyte levels (i.e. water)- fill it up and recharge on the maximum amperage setting on your charger. It may work- but for how long is anybody's guess- just be prepared to replace it. I had a "bulged" battery a few years ago and it ran for about 4 months after I first discovered the bulge- but it was pretty old anyways. I believe the problem with a frozen/partially frozen battery is that the electrolyte expands and can (can- but not necessarily always) shift the plates- shorting some or all of the cells internally.

replace it .

What kind of battery are u using??
I mean in canada it isn t that warm, why don t u use a gel battery??

I believe the problem with a frozen/partially frozen battery is that the electrolyte expands and can (can- but not necessarily always) shift the plates- shorting some or all of the cells internally.

Eric - exactly what my mechanic buddy told me this morning. I suspect I'll be shopping for a battery. :(

Thanks all for your feedback.

If its a sealed battery don't even bother recharging it. Its done for. The plates are most likely warped and shorted. If you attempt to recharge it or jump it, you are basically playing with a hydrogen bomb! Most likely the electrolyte levels are too low which is why it froze in the first place. My advice is get a new battery and be safe. Hope this helps! ;)

Jim
'80 Berlinetta