All the Sea Breathe systems run from a 12-Volt battery. The deck units can run from either the boat battery or an auxiliary battery. The requirements are that it should be a deep cycle sealed type battery. A small 32 amp/hour battery will allow about 90 minutes running on the single diver unit or 50-60 on the double diver. A typical boat "house" battery will allow several hours running on a deck unit. A word of caution, if you have the Sea Breathe connected to the engine start battery be careful not to run it too low to start the engine. It is better to use a separate battery if possible. There is much discussion about the merits of the different types of sealed deep cycle batteries. There are three basic types, Absorbed mat, gelled electrolyte or regular liquid filled. The absorbed mat and the gelled batteries are the most popular, as there is no danger of spillage if the case cracks. One important thing to remember about sealed batteries is that the method of charging is important. Always use a regulated charger that shuts off when the battery is fully charged. If you boil off the electrolyte there is no way to replace it and the battery life will be reduced. If a sealed battery is properly recharged it should last for several hundred cycles. Sea Breathe can supply a regulated battery charger if needed. Never leave the battery discharged for a long period, this will shorten battery life. Always recharge the battery as soon as convenient after use. Once fully charged a good battery will stay ready for use for months. Even sealed batteries must be recharged in a well-ventilated space. There is a misconception that sealed batteries do not give off hydrogen gas (Explosive). Even the sealed batteries will "off gas" through the vent valve if they are overcharged. The largest battery that will fit into the standard floating units is the 32 Amp Hour battery. This is a U1 type battery commonly used in mobility scooters. Some manufacturers rate them at 35 Amps but it is the same battery. The nominal dimensions are 7" high x 7.5" long x 5" wide, or 180mm high x 200mm long x 130mm wide. This size of battery is placed into the housing on its side. See the manual for more information on battery installation. Remember to check that the polarity is correct when you connect the cables. You do not need to disconnect the cables to the compressor when recharging the battery. If you intend to take your unit, with the battery, on an airplane you should make sure that the battery you have is approved for air transportation (many of the sealed batteries are). Some batteries have stamped into the case "Approved for Air Transportation" If not you should be able to get from the battery supplier a copy of the documentation confirming approval. The IATA Regulations require that the battery is disconnected and the terminals taped over with electrical tape. If you have any questions about battery care or selection you can e-mail or phone Sea Breathe.