Lithium Iron Phosphate Batteries (LiFePO4 or LFP)

by Tony Clark
(Perth Australia (Hills))

LFP Batteries protected by corrugated polycarbonate sheet

LFP Batteries protected by corrugated polycarbonate sheet

LFP Batteries protected by corrugated polycarbonate sheet
BMS, Battery cables and Battery fuses
Solar panel marshalling and Solar MPPT Charger

After 7 years of using second hand telecommunications batteries to power our (mainly) solar powered home, I had to bite the bullet and purchased a set of new batteries when a couple of cells failed.


After researching the options, I chose Lithium Iron Phosphate batteries, for their deep discharge ability, combined with long cycle life-time and stable battery voltage.

Where to get them??
I could have purchased them in Australia, but I would not have been able to afford as much battery capacity.
I was able to find a Chinese manufacturer who would ship a small (by their standards) battery.
I wanted to have about 20KWH capacity, which would have lasted ~3 days of overcast conditions. Due to cell availability, I settled on a cell capacity of 180AH, with 2 cells in parallel, 16 pairs in series to give a 360AH 48V (nom.). I paid the factory by international Foreign currency exchange and insured the consignment. I also chose an agent to handle the paperwork (Import duty and GST) at this end.
When it arrived, the Shipping agent contacted me by email and I paid the Government charges. There was an extra delay due to Customs deciding that they needed to xray the consignment to make sure I wasn't importing drugs or other contraband.
When I got the all clear, I drove to the shipping agent who loaded the crate onto my trailer and I took it home, unloading the crate while it was on the trailer.
A week later and the new battery was installed.
Actual battery voltage is between 52 - 54v at most times, dropping below 50V only at very low state of charge.

LFP batteries are easily damaged by over charge or under charge, so a Battery Management System (BMS) is essential. to protect the battery. (It disconnects the charge to prevent over voltage or disconnects the load to prevent under voltage).
I contacted EV Power (Australia) for a suitable BMS which was not expensive.

I used the existing Solar charger, adjusting the parameters to prevent excessive voltage being applied to the battery. I used the existing inverter, battery fuses and battery cables from the Lead Acid bank which this replaced.
This has been in reliable service now for over 6 months.

What do I do when it is overcast for a week or more? I also purchased a 48V 50A charger, for which I had a 15A outlet installed.

OK, I need to explain something else, While we are mainly solar powered, we still have mains power connected (3 phase) as we have pumps which need 3 phase power and our inverter is only single phase. So, if we run out of sun generated power, we can charge the batteries from the mains, using off peak power.


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