RE: Battery on Ground
A battery will discharge at the same rate, no matter if it is stored on concrete or not. Never let a battery sit for more than 6 months without being recharged.
Here is what battery manufactuerers have to say about battery storage:
Sealed Lead Acid Battery Storage
Power-Sonic Batteries should not be stored in a discharged state or at elevated temperatures. If a battery has been discharged for some time or the load was left on indefinitely, it may not readily take a charge. To overcome this, leave the charger connected and the battery should eventually begin to accept charge. Although Power-Sonic batteries have a low self-discharge rate which permits storage of a fully charged battery for up to a year, it is recommended that a battery be charged 6-9 months after receipt to account for storage from the date of manufacture to the date of purchase. Otherwise, permanent loss of capacity might occur as a result of sulfation. To prolong shelf life without charging, store batteries at 10 degrees Celsius or less.
Gaston: Lead-acid batteries previously were affected by long term storage after charging. But Gaston SLA batteries are not so affected. This battery offers longer extended storage than conventional batteries (referenced curve shows 3% per month self discharge rate at 20 degrees C.) During storage, carry out supplementary charging according to Table 3 (below 20 degrees charge every 6 months, 20 to 30 degrees C charge every 3 months, over 30 don't store). Although the self-discharge rate is low, specific precautions must be taken against the battery over discharging itself by self-discharge when in storage or not operating. In general, to optimize performance and service life, it is recommended that Gaston batteries which are to be stored for extended periods of time be given a supplementary charge, commonly referred to "top charging" periodically. The top charge referred to is a charge of 20-24 hours at a constant voltage of 2.4 volts per cell.
Spiral Wrapped Lead Acid Battery Storage
Hawker Energy Products
When a Cyclon battery is kept in storage, i.e. on open circuit, the ambient temperature should be controlled to prolong storage time and maintain maximum capacity over time. To get the best storage results, batteries should be charged at room temperature or below, and charged prior to being put back in service.
The OCV (open circuit voltage) of each battery must be monitored on an individual basis. If the OCV measures 1.93 Vpc, it has zero effective capacity and should be boost charged immediately. Even if the OCV reads higher than 2.00 Vpc at the end of 12 month's storage, the battery should be recharged before use. Thus, to maintain maximum reliability, batteries should be boost charged once every 12 months, or when the OCV reads 2.00 Vpc, whichever occurs earlier.
If the OCV is allowed to drop between 1.93 and 1.80 Vpc, some permanent damage may occur to the battery. However, if it drops to less than 1.80 Vpc, the battery will most likely be unchargable by conventional methods. Therefore, under no circumstances must the OCV be allowed to drop below 1.80 Vpc.
Just as high temperature accelerates the aging of a battery, so does it accelerate the self-discharge rate. Thus, when the storage temperature exceeds 25°C, one must monitor the open circuit voltage more frequently. . .
Flooded Lead Acid Battery Storage
Trojan: Periods of inactivity can be extremely harmful to lead acid batteries. When placing a battery into storage, follow the recommendations below to insure that the battery remains healthy and ready for use.
NOTE: Storing, charging or operating batteries on concrete is perfectly OK. The most important things to avoid: [ol][*] Freezing. Avoid locations where freezing temperature is expected. Keeping battery at a high state of charge will also prevent freezing. Freezing results in irreparable damage to battery's plates and container. [Freezing can happen between -19 F (40% charge) and -98 F (fully charged)][*] Heat. Avoid direct exposure to heat sources, such as radiators or space heaters. Temperatures above 80° F accelerate the battery's self-discharge characteristics.[*]Step by step storage procedure: 1. Completely charge the battery before storing. 2. Store the battery in a cool, dry location, protected from the elements. 3. During storage, monitor the specific gravity (flooded) or voltage. Batteries in storage should be given a boost charge when they show a 70% charge or less. Completely charge the battery before re-activating. [/ol] For optimum performance, equalize the batteries (flooded) before putting them back into service