Over their lifetime, batteries for the engine starting of a city transit bus must consistently deliver high cold cranking amps, which can be incredibly challenging during extremely cold weather. With the engine off, a high cycle reserve capacity is required to support loads such as interior lighting, blower fans, dash and monitoring systems, chair lifts and fare boxes. The alternator is the sole charging source for transit bus batteries, and undercharging is expected due to overloading the alternator. City transit bus batteries will often need to accept a high charge current after spending extended overnight periods in a discharged state. Alternator voltage is often poorly regulated, which may cause long-term damage to the batteries.

Battery failure is most commonly caused by acid stratification, extreme temperatures and destructive over-the-road vibration. Acid stratification naturally occurs in flooded lead-acid batteries and leads to a decline in capacity and charge acceptance. AGM technology and acid mixing technology for flooded lead-acid will mitigate acid stratification. A maintenance-free spillproof battery is highly desirable.

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.

The 12-volt DC system in a cruising powerboat is powered by a separate bank of ‘House’ batteries, which will be deep-cycled. The house batteries power GPS, electronics, radios, cabin and navigation lights, water, head and bilge pumps, and other dual power (AC/DC) appliances like refrigeration. The AC system is powered by ‘Shore Power’ or the on-board generator and supports items like electric stoves and ovens, TVs, cabin heaters and HVAC units. Dual power AC/DC refrigeration and straight AC loads like the microwave and TVs can also be powered by the inverter-charger.

The alternator charges house batteries after the starter batteries have been charged. When the boat is plugged into shore power or the generator is running, excess AC power is automatically shared with the inverter-charger, and the 12-volt house battery system is recharged. House batteries need to support the surge current of the inverter during load startup. State of Charge (SOC) monitoring will be advantageous.

The starting batteries must deliver high Cold Cranking Amps (CCA) consistently, operate at high and low temps and withstand vibration. With the engine off, High-Cycle Reserve Capacity (RC) is required to support special equipment such as winches, thrusters, etc. The engine alternator is the sole charging source for the starting batteries unless an independent shore-powered battery charger is installed. House batteries can often be connected to the engine to provide emergency starting. Maintenance-free spill-proof batteries are highly desirable in marine applications.

Deep-cycle battery specifications

Amp-hours (Ah); the current a battery can deliver for 20 hours at a constant discharge rate before the voltage drops to 10.5 volts. Cycle Life; Cycles represent the repeated charging and discharging of a full battery at 27°C / 80°F until the voltage drops to 10.5 volts and the battery fails to hold half its rated capacity. This ability to cycle repeatedly differentiates deep-cycle batteries from starting batteries or dual-purpose batteries, which can't withstand more than a few deep discharges beyond what they were designed for before their capacity degrade. Starting batteries are designed for maximum repeated discharges of 1-3% Depth of Discharge (DoD). Dual-purpose and high cycle batteries are designed for maximum repeated discharges of 17.5 – 30%Depth of Discharge (DoD). Depending upon technology, deep-cycle batteries are designed to withstand repeated depths of discharge of up to 50% to 80% Depth of Discharge (DoD).

Lead-acid battery failure is most commonly caused by acid stratification, extreme temperatures and destructive vibration. Acid stratification naturally occurs in flooded lead-acid batteries and leads to a decline in capacity and charge acceptance. AGM and acid mixing technology for flooded lead-acid starting batteries will mitigate acid stratification. AGM technology, or equalization charging by the inverter-charger for flooded lead-acid deep-cycle house batteries, will mitigate acid stratification.

The starting batteries for gasoline Inboard or Outboard motors must deliver high cold cranking amps (CCA) consistently, operate in high and low temps and withstand vibration. With the engine off, High-Cycle Reserve Capacity (RC) is required to support added electronic equipment such as GPS, depth finders, radios, navigation lights, bilge pumps, live wells, etc. The engine alternator is the sole charging source for the starting batteries. Maintenance-free spill-proof batteries are highly desirable in marine applications.

Starter battery specifications:

Cold Cranking Amps (CCA); the amps a 12V battery can discharge for 30 seconds at -18°C / 0°F while maintaining its voltage above 7.2 volts. Because lead-acid batteries produce more energy at higher temperatures, we also rate marine batteries in Cranking Amps (CA); similar to CCA but measured at 0°C / 32°F and Marine Cranking Amps (MCA); similar to CCA but measured at 27°C / 80°F

Higher cranking power is required for cold temperatures, diesel engines, or high-compression gas engines where high cranking voltage must be maintained for the fuel ignition systems to function. This requires maximum Amp Hours (AH) or Reserve Capacity (RC): Minutes a battery can maintain a load of 25 amps before it drops to 10.5 volts (at 27°C / 80°F).

Dual-purpose batteries must consistently deliver reasonable cold cranking amps (CCA), operate in high and low temps and withstand vibration. With the engine off, Reserve Capacity (RC) is required to support moderate electric loads such as electronic equipment, radios, house lights, bilge pump, small inverters, etc. From low to high, dual-purpose batteries can be designed with micro-cycle (17.5% Depth of Discharge - DoD) or high cycle (30% Depth of Discharge - DoD) life characteristics. Typically, the higher the cycle life ability, the lower the CCA rating will be in a dual-purpose battery. A battery with high CCA, High Reserve Capacity “and” long life should be viewed with suspicion.

Lead-acid battery failure is most commonly caused by acid stratification, extreme temperatures and destructive vibration. Acid stratification naturally occurs in flooded lead-acid batteries and leads to a decline in capacity and charge acceptance. AGM and acid mixing technology for flooded lead-acid starting batteries will mitigate acid stratification.

Marine Starting Battery Specifications

Cold Cranking Amps (CA), Cranking Amps (CA), Marine Cranking Amps (MCA)

Flooded starting batteries are the most popular lead-acid battery type for outboard motors. They often operate under the most extreme temperature conditions and must be able to deliver high Cold Cranking Amps (CCA) consistently. Starting battery failure is most commonly caused by acid stratification, extreme temperatures and destructive vibration. Starting batteries are not designed for regular discharges of more than 1% to 3% Depth of Discharge (DoD).

Marine Starting battery specifications

Cold Cranking Amps; the amps of a 12V battery can discharge for 30 seconds at -18°C / 0°F while maintaining its voltage above 7.2 volts.

Because lead-acid batteries produce more energy at higher temperatures, we also rate marine batteries in Cranking Amps (CA); similar to CCA but measured at 0°C / 32°F and Marine Cranking Amps (MCA); similar to CCA but measured at 27°C / 80°F.