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All About Batteries

Grid-tied solar is wonderful technology, and the lower electric bills and environmental stewardship are meaningful. Adding batteries to your solar system changes the game and adds energy independence and resilience to that mix.

With a properly engineered battery backup system, your refrigerator and freezer stay on, the well pump runs, and small appliances can be used. Harsh storms and utility problems can be gotten through much more comfortably. In addition, systems can be designed for long term preparedness to ensure that you have reliable uninterruptible power 24/7 for extended periods of time without utility power.

Battery Systems

mtvSolar offers two main types of battery systems: Schneider Electric and Tesla PowerWall. Each has their own strengths and weaknesses and best applications.

Tesla Powerwall

The most aesthetically pleasing of the two, Tesla PowerWall systems can be integrated with new or existing solar, supply 5kWAC per battery unit and can be stacked. Each PowerWall contains 12.2kWh of usable power, and this is additive with each additional PowerWall.

The Tesla lithium batteries are AC coupled, which makes integration a breeze, especially with existing systems. They are best suited for grid-tied implementations, rather than off-grid.

Schneider Electric

This is a system comprising of a Schneider hybrid inverter and either lead-acid or lithium batteries.

For large lithium backup or off-grid systems, we use Schneider XW series of equipment combined with the Harris battery solution. The Harris lithium batteries are American-made in Ohio using Lithium Iron Phosphate cells. They are available up to 26kWh in size and can be stacked.

When it comes to lead-acid, quality matters. Mountain View Solar uses DEKA/East Penn lead acid batteries, which are American Made in Pennsylvania using a sustainable manufacturing process. The lead in DEKA’s new lead batteries is recycled from old batteries (hence those core charges you get refunded upon return of a dead car battery).

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 acid.

For most lead systems we use the DEKA Unigy II line, an industrial AGM bank consisting of a single string of 2v cells. Originally intended for telecom backup systems, this battery bank is rated at 1800 cycles at 50% DOD, and can sit on stand-by for a decade or more!

mtvSolar commonly installs both types of systems. When approached for energy storage, we examine your individual needs including solar array size and shading, loads, required flexibility and autonomy, and then suggest the most appropriate system type.