In-Car Battery Storage
You could take the battery out of your vehicle during storage, but sometimes access can be a challenge. So it may be easier to leave it in. That's OK, but you should fully disconnect it to prevent parasitic drains.
First, check the voltage to ensure the battery has a full charge (about 12.6 to 12.8 volts for REDTOP®s and the 34M BLUETOP® and about 13.0 to13.2 volts for all other BLUETOP and YELLOWTOP® models). If it's not fully charged, give it a full charge prior to storage. Then, loosen the negative cable and disconnect it from the battery. All electrical draws on the battery will cease and your battery will be protected.
Batteries will lose some voltage while in storage for extended periods of time, but will typically have enough power to start your vehicle. Don't leave it up to the alternator to fully recharge the battery, as most alternators are designed to maintain batteries that are near a full state of charge, not recover deeply discharged batteries. Instead, use a battery charger to make sure your battery is fully charged. You'll extend the life of the battery and probably the alternator by doing this.
Will the battery discharge if left sitting on concrete?
No, today's batteries use polypropylene plastic for the case material. They will not be affected. When possible, always store a battery in a cool, dry location.