Which battery is best for Solar applications?

Which battery is best for Off-Grid Solar?

Off-grid batteries will be deeply cycled regularly and often operated in a Partial State of Charge (PSOC) situation. Off-grid batteries should be efficient so as not to waste valuable energy generated by solar or diesel generators. Off-grid batteries need high power capability to support the high surge draw, discharge and charge current of off-grid inverter-chargers. Access to off-grid sites is not always easy, so a maintenance-free battery is highly desirable. High and low temperatures need to be considered as this will affect the useful lifetime of the chosen battery. State of Charge (SOC) monitoring is critical for off-grid users and systems which rely on accurate battery SOC for functional operation.

Which battery is best for Whole Home Battery Backup?

By definition, a whole home backup inverter-charger backs up all the loads in the home. Therefore the battery needs to be able to support not only a high discharge rate but also deliver both high power output to support the startup surge of the inverter and be able to accept high charge current. Almost all inverters in this class are 48V DC input. When the backup batteries are used, they are likely to experience a deep discharge, but they will also spend a significant amount of time in Float. Autonomy needs vary, but often the system will be supported by a generator when long-duration blackouts are expected. Often, the battery storage room or closet in the home significantly impacts the physical size and configuration of the battery system. Temperature is not usually a concern. Access is usually not a concern, but many homeowners would prefer to live without maintenance complications. NOTE: If combined with solar, the whole home backup system will likely be used to take the home ‘off the grid’ to increase self-consumption, and if allowed, the inverter’s grid sell functionality will be used to lower energy purchase costs. If this is the case, the battery will be cycled regularly and may be often operated in Partial State of Charge situations (PSOC). Monitoring lifetime battery energy throughput will be significant to homeowners and grid management companies.

Which battery is best for Rural Microgrids?

The main concern for rural microgrid batteries is the amount of helpful energy capacity and the ability to scale up capacity to meet autonomy needs. The useful energy cost of the battery system will significantly impact the system's economics, as will battery efficiency, which will impact the operational costs. Ambient temperature, in combination with the battery room size at the site, will influence the selection of the battery. Remote location and availability of professional service will impact whether batteries must be maintenance-free. Remote battery status monitoring is beneficial for ensuring the battery system's proper usage and long life.

Which battery is best for Utility Surcharge Avoidance?

The inverter chosen to avoid utility surcharges by supplying supplemental energy will be the driver for battery selection. Solar integration will be mandatory in some utility jurisdictions. The battery will need to handle micro cycling and partial state of charge operations. Efficiency and energy density will be important. Safety certifications will be mandatory in many jurisdictions.

Many inverters that provide Whole Home Backup also incorporate grid support functions. The same criteria will drive the choice of battery used by these systems for the whole home application. These battery systems will all be 48V.

High-frequency grid-tie inverter systems that target residential self-consumption and avoidance of time-of-day usage charges are generally sold as an integrated package with a preselected high-energy density battery. These batteries are predominately high-voltage lithium for system efficiency and are specifically designed to match the inverter's very high DC input voltage (400V ~ 500V). These inverters typically provide minimal backup runtime and no surge support. Therefore, a battery with a high surge current is not required, and moderate discharge and charge current rates are usually sufficient. High-voltage batteries for this application will be maintenance-free and require a secure enclosure with restricted access due to the high voltage. Monitoring lifetime battery energy throughput will be significant to homeowners and grid management companies. Lead-acid batteries no longer feature these types of inverters.