Why We Chose The Batteries That We Use
There are two battery types commonly used with solar: lead-acid and lithium-ion. Each type has its pros and cons:
Lead acid has a lower cost per kWh, excellent surge capability, can withstand cold temperatures, and are readily available. However they are very heavy, somewhat large and have a lower cycle life compared to lithium.
Lithium has a very high energy density and extremely long cycle life, however they have a high cost per kWh, often lower surge capability and suffer substantial capacity loss in below freezing temperatures.
The standard battery for solar applications is lead-acid, especially if grid-tied battery backup. In these situations, the battery sits on float most of its life, until the power goes out. Therefore, the lower cycle life isn’t of much concern. For off-grid situations, lithium can (but not always) be better as the battery is cycled daily and at different states of charge, therefore they can outlast lead-acid many times over.
At Mountain View Solar, we will choose the battery type that makes the most sense from a technical standpoint for a given application. We consider space, power requirements, operating temperature, cost and equipment availability amongst a few important design considerations.
When it comes to lead-acid, quality matters. Mountain View Solar uses DEKA/East Penn lead acid batteries, which are American Made using a sustainable manufacturing process. Most of the lead in DEKA’s new lead batteries is recycled from old lead batteries.
The lead batteries that we use are of the deep cycle variety, meaning they are built with thicker plates to withstand heavier use. Compared to a typical starting battery, they are much more robust and capable when drawn down repeatedly. Additionally, they are sealed or SLA type lead-acid. We do not install flooded batteries which emit dangerous gases and can leak caustic acid.
For smaller systems we utilize DEKA’s GEL group size 8D batteries. We typically use a max of 8 of these batteries before moving up to the industrial grade Unigy II rack of 2v cells. This is because having multiple strings of batteries in parallel results in an unbalanced bank that over time degrades more rapidly. The DEKA GEL batteries have a cycle life of 1000 cycles at 50% depth of discharge, and will last many years in stand-by battery backup applications.
For larger systems we use the DEKA Unigy II line, an industrial AGM bank consisting of a single string of 2v cells. This battery bank is rated at 1800 cycles at 50% DOD, and can sit on stand-by for a decade or more!
Mountain View Solar has the most off-grid and battery backup experience in the mid-atlantic area. Our current systems are based on Schneider Electric and DEKA equipment, resulting in a clean and compact system, built to last over twice as long as competitor’s designs.