More important from the point of view of cold-storage, however, is that even a partially discharged battery will freeze at temperatures as high as 20 F. If a battery is allowed to freeze, it may be damaged internally or, worse, the case may crack. A fully charged battery's freezing point, on the other hand, is somewhere around minus 95 F. Additionally, flooded batteries experience a self-discharge of approximately 1 percent per day at room temperature, which means they should be recharged at least monthly. Because their metabolism increases as the thermometer rises, they discharge more rapidly at higher temperatures, so more frequent recharging is often necessary in the tropics. Because of this phenomenon, chances are good that if you store your battery aboard in cold climates and make sure that it's fully charged when you put it to sleep, it will maintain this charge, provided no loads are present, for several months. Thus, cold storage is actually preferable. Periodic charging, monthly or as needed, will ensure that the battery remains topped up and that it resists freezing and sulphation. (Note: Never charge a battery that's been or is suspected of having been frozen. It must first be thawed and inspected for damage.) If you're using a temperature-compensated charger-and you should be-don't be surprised to see charge voltages as high as 15 volts when the mercury is in the nether regions. This is normal for cold batteries, and it's just what they need when they're in this frosty state.