LiFePO4 TECHNOLOGY INFO
Lithium Iron Phosphate Battery (LiFePO4)
Features and Benefits When Compared To SLA
This information will cover the features and benefits of Lithium Iron Phosphate (LiFePO4) batteries when compared to traditional Sealed Lead Acid (SLA) battery technology. Since the discussion is around LiFePO4 and SLA, the article concentrates on 12VDC and 24VDC applications.
Different Lithium Technologies
It is important to note that there are many types of “Lithium Ion” batteries. The point to note in this definition refers to a “family of batteries”.
There are several different “Lithium Ion” batteries within this family which utilize different materials for their cathode and anode. As a result, they exhibit very different characteristics and therefore are suitable for different applications.
Lithium Iron Phosphate (LiFePO4)
Lithium Iron Phosphate (LiFePO4) is a well-known lithium technology in Australia due to its wide use and suitability to a wide range of applications.
Characteristics of low price, high safety and good specific energy, make this a strong option for many applications.
LiFePO4 cell voltage of 3.2V/cell also makes it the lithium technology of choice for sealed lead acid replacement in a number of key applications.
Of all the lithium options available, there are several reasons why LiFePO4 has been selected as the ideal lithium technology for replacement of SLA. The main reasons come down to its favourable characteristics when looking at the main applications where SLA currently exist. These include:
- Similar voltage to SLA (3.2V per cell x 4 = 12.8V) making them ideal for SLA replacement.
- Safest form of the lithium technologies.
- Environmentally friendly –phosphate is not hazardous and so is friendly both to the environment and not a health risk.
- Wide temperature range
Features and benefits of LiFePO4 when compared to SLA
Below are some key features LiFePO4 batteries which give some significant advantages of SLA in a range of applications. This is not a complete list, however it does cover the key items. A 100AH AGM battery has been selected as the SLA, as this is one of the most commonly used sizes in deep cycle applications. This 100AH AGM has been compared to a 100AH LiFePO4 in order to compare a like for like as close as possible.
Feature – Weight:
- LifePO4 is less than half the weight of SLA
- AGM Deep cycle – 27.5Kg
- LiFePO4 – 12.2Kg
- Increases fuel efficiency
- In caravan and boat applications, towing weight is reduced.
- Increases speed
- In boat applications water speed can be increased
- Reduction in overall weight
- Longer runtime
Feature – Greater Cycle Life:
- Up to 6 time the cycle life
- AGM Deep cycle – 300 cycles @ 100% DoD
- LiFePO4 – 2000 cycles @ 100% DoD
- Lower total cost of ownership (cost per kWh much lower over life of battery for LiFePO4)
- Reduction in replacement costs – replace the AGM up to 6 times before the LiFePO4 needs replacing
Feature – Flat Discharge Curve:
- At 0.2C (20A) discharge
- AGM – drops below 12V after
- 1.5 hrs of runtime
- LiFePO4 – drops below 12V after approximately 4 hrs of runtime
- More efficient use of battery capacity
- Power = Volts x Amps
- Once voltage starts to drop off, battery will need to supply higher amps to provide same amount of power.
- Higher voltage is better for electronics
- Longer run time for equipment
- Full use of capacity even at high discharge rate
- AGM @ 1C discharge = 50% Capacity
- LiFePO4 @ 1C discharge = 100% capacity
Along with this the effect of Peukert’s law is much less significant with lithium than that of AGM. This results in having available a large percentage of the capacity of the battery no matter what the discharge rate. At 1C (or 100A discharge for 100AH battery) the LiFePO4 option will still give you 100AH vs only 50AH for AGM.
Feature – Increased Use of Capacity:
- AGM recommended DoD = 50%
- LiFePO4 recommended DoD = 80%
- AGM Deep cycle – 100AH x 50% = 50Ah usable
- LiFePO4 – 100Ah x 80% = 80Ah
- Difference = 30Ah or 60% more capacity usage
- Increased run time or smaller capacity battery for replacement
Feature – Greater Charge Efficiency:
- AGM – Full charge takes approx. 8 hours
- LiFePO4 – Full charge can be as low as 2 hrs
Battery charged and ready to be used again more quickly
Another strong benefit in many applications. Due to the lower internal resistance among other factors, LiFePO4 can accept charge at a much great rate than AGM. This allows them to be charged and ready to use much faster, leading to many benefits.
Feature – Low Self Discharge Rate:
- AGM – Discharge to 80% SOC after 4 months
- LiFePO4 – Discharge to 80% after 8 months
- Can be left in storage for a longer period