Pros and Cons of Lead Acid & Lithium-Ion Chemistries for Energy Storage
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.
Lead Acid
Currently, the are three common lead-acid battery technologies: 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 destroyed. They also require the terminals to be periodically cleaned. These are used in many small off-grid homes, because they have the cheapest upfront cost. However, over the course of 20 years, they can double their cost or more, compared to many Lithium Ion battery types. Of the Lead Acid batteries, there are also sealed batteries that don’t require watering, called 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 than Flooded and are very good at being on “Stand By”, fully charged, in the event of a power outage.
Lithium Ion Batteries
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 charged at a faster rate. Less energy is wasted 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, reputable 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.
LiFePO4: PRISMATIC
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 resistant, rigid plastic case. LiFePO4 is also the most stable and safest 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. Prismatic cells can also be replaced in the field, unlike the other two options. These cells are ideal for existing off-grid systems that are switching from lead acid batteries. With offices in Hawaii and California, Atlas AES manufactures battery products in multiple sizes, using these cells.
LiFePO4: POUCH
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 accommodate 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 example of this kind of battery. This battery is also one of the few that are currently compatible with the SolarEdge line of StoreEdge inverters. However, this is our 2nd choice for a battery product, because of it’s limited use cases. Sometimes, it is not possible to backup house circuits, because the electrical sub-panel may be located in a remote location. In those cases, we can install two 20a 120V outlets next to the inverter, that can be used, in the event of a power outage. Those outlets can be used, via an extension cord, to power refrigerators, freezers, microwaves, dishwashers, computers, etc. Not ideal and or automatic, but very handy.
LiNMC: Cylindrical
Lithium Nickel Manganese Cobalt (LiNMC) Small Cylindrical 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 2019, we expect to have some products available to make use of the Powerwall for Off-Grid applications as well. Because this product will work well in almost every situation, this is our 1st choice. While this battery’s cost is $6,700, this does not include shipping or the additional required hardware and the labor to install it. The typical cost for a single Powerwall, installed, is $10,000 and about $9,000 for subsequent Powerwalls on the same system. The Powerwall is the best price for performance battery product that we have seen to date. It is the only battery product with a liquid thermal management system and an Over The Air (OTA) firmware update system that adds additional functionality, to make the product better over time. It is also the only battery with a 10 year warranty with unlimited cycles.