There are several different types of Lead Acid and Lithium-Ion batteries. We are going to review the most widely used batteries as well as the best options available today.
Currently, the three three common lead-acid battery technologies are Flooded, Gel, and AGM. Flood lead-acid batteries require a lot of maintenance and refilling the water in the cells. While there are automated filling techniques, if that system fails or you forget to water your batteries one too many times, they can be easily detroyed. They also require the terminals to be periodically cleaned. These are used in may small off-grid homes, because they are the cheapeast upfront cost. However, over the course of 20 years, they can be double the cost or more, than many Lithium Ion battery types. Of the Lead Acid batteries, there are also sealed batteries that don't require watering, called are AGM and Gel. Of the two, we believe that AGM is a better solution for Solar Energy storage. No watering and just the occasional terminal cleaning, makes these batteries appealing to many. However, they cost more than Flooded (wet) batteries. AGM batteries are best suited for very shallow depth of discharge applications and also battery backup solutions. AGM batteries can also handle a higher discharge rate then Flooded and are very good at being on "Stand By", fully charged, in the event of a power outage.
Of the Lithium Ion battery technologies, the below three types are the most widely available options we have today. In general, Lithium Ion batteries cost more, upfront, than Lead Acid batteries, but cost much less over time, because their service life can be 10-20+ years. Lithium Ion batteries also have a much higher charging efficiency when charge at a faster rate. Less energy is waisted, as heat, when charging Lithium Ion batteries, which gives you more usable energy from your solar system. They also take up much less space and weigh only a fraction of what Lead Acid batteries weigh. Only purchase Lithium-Ion batteries from a well known replutable, name brand company, such as CALB, Sinopoly, GBS and Winston. There are many chinese manufactures that sell sub-standard and "knock off" cells that may be labeled as if from a name brand company.
Lithium Iron Phosphate (LiFePO4 or LFP) PRISMATIC cells are the highest quality, longest lasting type of Lithium Ion cells that you can get, today, for solar energy storage. These battery cells are housed in a tough, puncture resitant, rigid plastic case. LiFePO4 is also the most stable and safe of the Lithium Ion battery chemistries. Prismatic cells are a little heavier and take up more space than pouch cells, but provide the highest level of safety. They also tend to cost more than the other two options, because they cost more to manufacture. Prismatic cells can also be replaced in the field, unlike the bottom two options. These cells are ideal for off-grid, on-grid with battery backup and on-grid self consumption Solar PV systems, such as with MECO's Customer Self Supply (CSS) program. With offices in Hawaii and California, Atlas AES manufactures battery products in multiple sizes, using these cells. This is our 1st choice as a Lithium Ion battery recommendation, if the customer's budget allows.
LiFePO4 POUCH cells, compared to prismatic, are cheaper to manufacture, lighter, take up less space and can be manufactured in a variety of shapes and sizes to accomodate a variety of needs, including wall mount installations. However, pouch cells are soft, with only a very thin layer of material covering the cell. This is why manufactures, protect their pouch cells in an all-encompassing rigid type enclosure, to protect the cells. The LG Chem product, RESU10H, is a good examples of this kind of battery. This battery is also one of the few that are currently compatible with the SolarEdge line of StoreEdge inverters.
Lithium Nickel Manganese Cobalt (LiNMC) Small Cyclindrical cells are the cheapest to manufacture of the Lithium Ion batteries. They are small, lightweight and can be configured in a variety of shapes and sizes, like pouch cells. Companies, such as Tesla, use advanced monitoring and cooling in their budget friendly Powerall product. This battery can be hung on a wall or on the ground. The Powerwall is well suited for on-grid with battery backup and on-grid self consumption Solar PV systems. By Summer of 2017, we expect to have some products available to make use of the Powerwall for Off-Grid applications as well. While this battery's cost is $5,500, this does not include the additional required hardware or the labor to install it. The typical cost for a single Powerwall, installed, is $8,500 and about $7,000 for subsequent powerwalls on the same system. The Powerwall is the best price for performance battery product, that we have seen to date. Besides, the included 10 year warranty, you can also buy a 10 year extended warranty for $1,400, for a total of 20 years.