The long-term life rating of a battery is the total number of charge/discharge cycles that are available in a battery. This rating is calculated at a designated depth of discharge and C rating for that particular battery. The batteries that we carry are rated for 3000 cycles at 80% depth of discharge at 1C, which is very aggressive.
LiFePo4 battery systems have a consistent voltage that is regulated by the battery management system. Typically the voltage for a 12V rated battery will be 12.6-12.8V over the course of the entire battery cycle. The typical voltage over the course of a cycle for a lead acid battery will drop from 13V to 10V, which leaves a significant amount of power left unavailable because of the voltage decay.
In simple terms, battery efficiency is the measurement of a battery’s capability to accept and expel energy. Lead acid batteries range in efficiency from 25%-40%, opposed to a LiFePo4 efficiency rate of 98%. This means that I can use 98% of the energy stored in a LiFePo4 battery and that it will accept 98% of the energy that I try to put into it for storage.
Weight & Space
LiFePo4 batteries don’t contain lead or fluid, which is the main reason why they don’t weigh nearly as much as lead acids. Due to battery efficiency, fewer batteries are required to do the same amount of work. This combination means significant savings in the weight and space required for a LiFePo4 energy storage system.
The “C” rating of a battery is a measurement of the rate of energy transfer that a battery can handle continuously. This is crucial to battery performance and ultimately what a battery can be used for because it is the limiting factor in an energy storage system. For example, if a 100Ah battery is rated at 2C charge, 1C discharge, this means that the battery can be charged at 200 Amps and discharged at 100Amps. If I have an electrical load that requires more than 100 Amps, this battery will not work for that application.
The C rating is also used when determining the long-term life of a battery. If a battery has to work hard (discharge or charge at a high capacity) it will not last as long so manufacturers rate how much the battery can handle and yet retain a reasonable amount of cycles. For example, a cycle rating for a battery may read like this: 2000 cycles @ 80% depth of discharge @ 0.5C. This means that using the same 100 Ah battery, I will be able to charge and discharge that battery 2000 times if I use 80Ah/cycle at no more than a 50Amp load. If I use a 100Amp load, it will overwork the battery and even though the battery may be capable of providing that load, it will reduce the long-term life of the battery.
Neverdie Battery Management System
The battery management system for the LiFePo4 we offer regulates the voltage of the system and monitors the depth of discharge. It will automatically shut the system off when it reaches 90% depth of discharge to prevent the system from being damaged due to over discharge. This also allows a reserve capacity for emergency situations where extra power may be needed for a short time.
The total amount of energy that can be charged/discharged from the battery over the course of its lifetime measured in kWh. (Calculated as (battery capacity x depth of discharge x battery efficiency x total cycles x avg cycle voltage)/1000)
LiFePo4 batteries have an incredible power density rating thanks to a great long-term life, high battery efficiency, consistent voltage output, and a high C rating. The reduced weight and space is beneficial in system design as it can eliminate the need for additional construction costs for housing and supporting the energy storage system.
LiFePo4 12V100Ah battery
Power density: 2,963.5 kWh
[(100Ah x 80% depth of discharge x 98% efficiency x 3000 cycles x 12.6V)/1000]
Typical Lead Acid 12V100Ah battery
Power density: 132 kWh
[(100Ah x 50% depth of discharge x 40% efficiency x 600 cycles x 11V)/1000]