DEEP CYCLE (FLOODED BATTERIES)

When selecting solar batteries (deep cycle), you'll have the option to use flooded lead acid (FLA) batteries or sealed batteries (AGM or Gel cell).  Keep in mind that FLA batteries require a bit of maintenance, however, they generally last longer than their sealed counterparts. Water Miser Vent cap - Reduces Battery Watering can reduce the frequency that the deep cycle batteries need watering.  You'll need one vent cap for each 2 V cell.  Desulfater are another good low cost investment that can help prevent sulfation and boost the performance of the batteries.  Flooded Lead Acid batteries can build up sulfate crystals on their lead plates over time. 

Sealed deep cycle batteries may be a bit heavier and therefore cost a bit more to ship.  Deep cycle batteries come in many sizes: from sealed batteries that are less than 10 pounds to flooded lead acid batteries that weigh over 200 pounds each!  They can be small (and fit in a backpack) or large (2'x 2'x 1') and anywhere in between.  Generally the size and weight correspond with amp hours of storage.  So if you need a lot of electrical storage, be sure that you have the appropriate space to house the batteries.