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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.

How do Batteries Work?


Batteries are chemical energy storage devices.  Most of us know a battery as an encased unit that can retain potential energy to be discharged as electricity. The differences in batteries arise from the materials used to create their component parts, namely the electrolyte and the two electrodes of different materials. When connected into a circuit, ions from one electrode move through the electrolyte (the conductive material around the electrodes and between them) into the other electrode, creating a flow of energy that manifests as electrical current. Many modern advanced technology batteries are fully sealed, with the electrodes connected to an external anode and cathode that conduct the electricity in and out of the battery. Other batteries require the addition of water to maintain the optimum levels of electrolyte concentration.


Each cell (a unit containing the two electrodes and the electrolyte) in a rechargeable battery (made up of one or more cells) uses the two electrodes to generate energy. The materials have been chosen because they can react and produce electricity that flows out of the battery (called discharge) as well as reverse the chemical reaction by receiving electricity from another energy source (called recharging). Over the years, people have discovered different combination of electrodes that meet a few important criteria:


Two Most Popular Types of Batteries


Lithium-Ion
– Given their reputation for being smaller and lighter, as well as having long cycle lives, these batteries are becoming more common for residential battery storage. Mountain View Solar offers multiple types of lithium battery. They do need climate control to maintain peak operation, but overall these are perfect for running critical systems in a residential setting, such as refrigerator, electronics and other small appliances. 


Lead-Acid
– Highly consistent, Lead-Acid batteries can be applied to any size project as they can be scaled up infinitely for the largest applications. They do have a lower depth of discharge than Lithium, so they require a larger overall capacity for the same true energy output, and they can be a bit complicated and require specialized labor to install. Some versions are flooded and require watering and maintenance, but for safety reasons Mountain View Solar will only install sealed, maintenance free batteries, so there isn’t a chance of gases or acid leaking from them.  Lead acid batteries are a very well-tested, established technology.  The DEKA Unigy II industrial grade batteries that we recommend and install were originally designed for backup in the Telecom industry, so they are very well suited for residential and commercial backup with extremely long stand-by lifespan.  Although lead is a toxic heavy metal, the lead in DEKA’s lead acid batteries is recycled from dead batteries; the recycling system for lead-acid batteries is well established.


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.


mtvSolar offers multiple types of battery systems:

  • Tesla PowerWall

  • SolarEdge EnergyHub

  • enPhase enCharge

  • Schneider + Lithium or Lead Acid


Each has their own strengths and weaknesses and best applications.


Tesla PowerWall
is a lithium-ion battery for your home. It allows you to store power that can then be used in the case of an AC coupled power outage or, for solar owners, to store excess power produced by the panels. Although not specifically tied to solar as a technology, one can easily see how the PowerWall works very nicely with a solar installation. 


The Tesla PowerWall builds on the expertise and technology of Tesla’s engineers to produce a lithium-ion battery that is small enough to reside neatly out of the way in your home, but powerful enough to provide meaningful electricity when you need it.  PowerWall is great for time of use shifting and backup, but not recommended for off-grid scenarios due to the AC coupling and lack of proper generator support.

  • Compact and Simple – PowerWall is a completely automated system that installs easily and requires no maintenance.

  • Completely Safe – Liquid thermal controls and touch safe technology maximize battery life and safety.

  • Control Your Energy – Seamlessly monitor and automatically manage your Powerwall, solar panels, Model S or X with the Tesla App.

  • Stay Protected – Reserve a certain percentage of your Powerwall to protect your home from a utility outage and extend the hours of backup.

  • No generator charging


EnergyHub
is a combination of a SolarEdge EnergyHub inverter with SolarEdge lithium battery. These systems have the following major benefits:

  • Wall mounted lithium battery storing ~10kWh

  • Optimized DC coupled Solar

  • 10 year battery warranty

  • Can stack up to 3 10kW EH inverters with up to 3 batteries each

  • Generator charging

  • Charge your EV during an outage


EnPhase enCharge
“The Enphase Encharge 10 all-in-one AC-coupled storage system is reliable, smart, simple, and safe. It is comprised of three base Encharge 3™ storage units, has a total usable energy capacity of 10.08 kWh and twelve embedded grid-forming microinverters with 3.84 kW power rating. It provides backup capability and installers can quickly design the right system size to meet the needs of both new and retrofit solar customers.” -enPhase Marketing

  • Ten-year limited warranty

  • Passive cooling (no moving parts/fans)

  • Grid-forming capability for backup operation

  • Support for self consumption

  • Lithium iron phosphate (LFP) chemistry for maximum safety and longevity

  • Generator charging


Schneider Electric
is a system comprising of a Schneider hybrid inverter and lead-acid or lithium batteries. These systems have the following major benefits:

  • The technology has been around for decades

  • Unlimited battery and inverter scalability

  • Can fire up anything in your home

  • Can tie in a generator for battery charging and use it interactively

  • American-Made batteries available


The downside is they are labor intensive and more complicated.  These systems are especially great for off-grid applications.  Note that we do not install flooded batteries; therefore there is no danger of dangerous gases or leaking acid.


Commercial Applications


Demand charges are adders that utility companies charge commercial customers to ensure that they can deliver the maximum power ever needed by the client.


Demand charges are based on the highest 15-minute average usage recorded within a given month. If the facility tends to use a lot of power over short periods, the demand charges will comprise a larger part of the bill. If the facility uses power at a more consistent rate throughout the month, the demand charges will generally be a smaller part of the bill.


In our area we’ve seen bills where demand charges comprise 50% or more of the total.  The good news is that Mountain View Solar can help you slash demand charges in three ways:

  • Install a solar PV array which will lower overall power usage, including demand charge during the day.

  • Install battery storage to store power and release it as needed during periods of peak load, therefore reducing demand charges from the utility. This implementation is called “peak load shaving”.

  • Analyze power usage to help further reduce demand charges by changing how equipment is turned on, or adding controls to reduce surge loads.


Unlike a generator, which requires time to come online and power loads, mtvSolar’s battery systems supply power immediately and silently, eliminating possible interruptions in critical infrastructure operation. They are also maintenance free.


We believe the best way to charge a battery is with solar. mtvSolar can integrate a solar PV array with the battery storage. Even a small array can extend the battery autonomy by many days.