Deep cycle lead-acid batteries are mainly divided into three types: Flooded lead-acid batteries, Absorbent Glass Mat (AGM) batteries, and Gel batteries. The first is inexpensive and has a long lifespan, but requires regular maintenance to keep the electrolyte in balance with the water inside the battery case. The other two fall into the broader category of sealed lead-acid batteries. While they're designed to be maintenance-free by sealing the electrolyte inside the case, they're also more expensive and likely won't last as long. Those unfamiliar with deep cycle batteries may also know little about the difference between the three, and may even be mistaken.

    Flooded lead-acid batteries are the simplest and cheapest deep cycle batteries. But their maintenance is also complicated, requiring regular additions of distilled water. If properly cared for and regularly discharged to no more than half of their capacity, FLA batteries can last 5 to 8 years in a home energy storage installation.

    The sealed lead-acid (SLA) battery inside the sealed lead-acid battery cannot be opened and does not require water. There are two main types of SLA batteries: Absorbent Glass Mat (AGM) and Gel batteries.

(一) AGM batteries (absorbent glass mats): High-quality AGM batteries can be discharged to 80% of their capacity after hundreds of cycles, and typically last 4 to 6 years in-home energy storage devices.

However, these advantages come at a cost, with AGM batteries typically costing 1.5 to 2 times more energy per kilowatt-hour (kWh) of energy stored. AGM batteries also take up more space per kWh, but again, they can be placed sideways to save space in home storage setups.

(二) Gel batteries: Gel batteries are the safest lead-acid batteries because they release very little hydrogen from the exhaust valve. They perform well where high temperatures are a concern and can emit less than 50% and maintain their useful life. Additionally, gel batteries require careful charging using specific smart chargers designed to limit the voltage used to charge the battery and prevent overcharging. Not using these chargers can cause the battery to drain years early.