“While it may seem like a waste of a functioning battery, the safest thing is to replace it.
While repairing it using welding techniques could last a few days, it’s not a permanent solution. If it cracks again, it has the potential to cause damage to your car, shut down the engine, and pose a risk to you.
You may be able to visit an auto store like AutoZone or Advanced Auto Parts. Once you purchase a battery, they can typically install it for you. Normally, they’ll also recycle or properly dispose of your damaged battery.