A lot of our recent SAPs inquiries have had customers ask about LiFePo batteries or Lithium Iron Phosphate cells. These batteries have only been in the Australian market now for 2-3 years with very few distributors/resllers having any real installation experience. LiFePo batteries offer 3 main benefits over traditional Gel or sealed flooded cell batteries, these being; they are smaller and lighter, they have a designed depth of discharge of 80% vs 50% for sealed batteries and they theoretically have a far greater cycle life.
LiFePo batteries are typically 3-4 times more expensive than conventional sealed flooded cell batteries. Common cost comparisons typically do not take into account the correct DoD (Depth of Discharge) for a Stand Alone Power System but compare their designed DoD and therefore claim that utilising LiFePo can enable you to use an almost half size Ah battery bank when compared with Gels.
These calculations are often incorrect when it comes to comparing these battery technologies in a Stand Alone Power System which all typically require 3 days of Autonomy. Hence you need to work with a 30% DoD for both battery technologies, regardless of their designed DoD.
I typically suggest to our SAPS customers to run with Gels for these primary reasons;
1. A battery is only as good as the system design it is being installed into. Given that Gel batteries can last in excess of 20 years, spending 4 times the amount of LiFePo batteries may not always be beneficial.
2. LiFePo batteries are typcially all 48V cells, which means should a cell fail for what ever reason, you are up for considerable expense to replace, approx. 15K vs $1000 for a 2V single gel cell.
3. LiFePo batteries require a constant voltage of 14.7V which is controlled by a BMS or Battery Management System. If this on board management system fails, it can distroy the battery almost immediately.
LiFePo batteries do however have their benefits in applications where size and weight are an issue. Marine and portable power applications are often ideal for LiFePo battery technology.