LiFePO4 - Lithium iron phosphate battery

Lithium Iron Phosphate LiFePO4 battery are very different from the car battery. Lead-acid batteries are a mixture of lead plates and sulfuric acid and have been around since 1859.

In the meantime, there are solutions for the disadvantages of this battery. One of them has been the Lithium-ion batteries for commercial use for more than 35 years since 1980.

The lithium technology has become a proven technique for use in small electronics such as laptops and wireless instruments. It has primarily displaced NiCad (nickel-cadmium) from the market. Thanks to its many benefits.

LiFePO4 - Lithium iron phosphate battery

The lithium technology has also been negative in the news in recent years due to several cases where the safety of lithium-ion cells has been discussed.

The most common is the Lithium-Cobalt-oxide (LiCoO2) variant. Which is sensitive to overheating if you overcharge the battery. This can lead to spontaneous combustion, and a lithium fire is hot and fast, which can have significant consequences.

Lithium Iron phosphate cells:

The previous is also the reason that heavier applications rarely use lithium. However, new lithium chemistry was developed in 1996, Lithium Iron Phosphate ( LFP ). The LiFePO4 cells have a lower energy density and are many times safer than LiCoO2 cells. If we look at the benefits of LFP, there is actually no reason to choose a different battery technology.

Which battery is most suitable for solar energy storage?

  1. Useful capacity:
    In contrast to lead-acid batteries, a LiFePO4 battery can use more than 100% of the nominal size. If you take a 100 Ah battery, you can actually only use 30 to 50 Ah of the capacity with lead-acid, while this is more than 100 Ah with a LiFePO4.
  2. Longer longer cycle life:
    Research has shown that 2000 to 5000 cycles can be expected from a lithium lifepo4 battery. These are theoretical results, but recent measurements show that this type of cell has more than 75% of its capacity after 2000 cycles.A lead-acid battery, on the other hand, will fail after only 300-500 cycles, with particular attention to maintenance and proper use.
  3. Fast and efficient loading:
    A 100% capacity charge can be done very quickly. Lead batteries require an absorption phase to load the last 20% of the capacity. If the charger is powerful enough, you can charge the LiFePO4 battery extremely quickly. Even within 30 minutes.If the battery is regularly not fully charged, this is not a problem. Unlike a lead battery, the Lithium will have no damage. This takes away many of the concerns that people usually have about the battery and makes it very flexible.
  4. Little lost energy:
    They charge with an efficiency of almost 100% compared to 85% for the vast majority of lead batteries. This efficiency is especially important when using solar cells and energy backup.
  5. Climate resistance:
    Both lead-acid and LiFePO4 lose capacity in cold environments. With the LiFePO4, however, this loss is minimal. For example, it has an ability of 80% at a temperature of -20˚C, whereas this is only 30% with an AGM lead battery. LiFePO4 is also the logical choice for use in extreme cold and heat, hence the high demand for these batteries in the professional world.
  6. Easier to install:
    Can be mounted in any position and, moreover, the room does not have to be ventilated. They weigh only a quarter of the enormous weight of their lead equivalent.
  7. No maintenance:
    They do not require maintenance. The "Battery Management System" ensures that all cells are being charge and in balance proportionally. The battery only needs to be charged, and it is ready for use. This charging can be done one hour before use.
  8. Loss of stress:
    The discharge curve is almost flat. Which means that a battery with 20% capacity can give the same output as a fully charged battery. And prevents many of the problems that lead batteries have during discharge. Another significant fact is the enormous peak load that a LiFePo4 can deliver, even if it is already fully discharged.
  9. Weight and size:
    The weight is only a fraction of their lead equivalent, and the dimensions are also considerably more favourable.

LiFePO4 - Lithium iron phosphate battery

LiFe cells are much safer than other types of batteries. There is no risk of explosions in case of overcharging, overheating, short-circuiting and damage; this in contrast to lithium-ion or lithium polymer batteries. So the best candidate battery for solar energy storage!

Therefore RCT-power and BYD batteries are using this kind for the safety and high cycle time.

LiFe cells have many advantages:

  • The short charging time
  • Durability
  • Low weight
  • Environmental friendliness
  • Long service life

There is only one disadvantage: the LiFe batteries are currently still costly. Moreover, lithium lifepo4 battery technology is subject to several patent disputes, so that manufacturers are looking for equally performing chemical variants.

All these characteristics make Li-Fe batteries ideally suited for laptops, UPS systems and battery tools and ultimately hybrid cars. ( V2G electric cars )

Phosphates and environment:

Phosphates significantly reduce the disadvantages of cobalt, in particular, costs, safety and environmental unfriendliness.

On the other hand, the energy density is 14% lower. They investigate a higher energy variants. Due to the much better safety characteristics of phosphate. Therefore, compare to the current lithium-ion cobalt cells, they produce batteries with more giant cells without having to rely on extra safety measures.

The first rechargeable lithium produced Li-Fe cells works with a voltage of 3.2 Volts and a capacity of 1200 mAh. Non LFP rechargeable battery´s are also available in the standard AA format, with 1.5 Volt voltage and 2900mAh capacity.

Lithium ion Polymer batteries:

LiPo use a dry, flexible polymer as the electrolyte. This dry polymer naturally has poor conductivity and a high internal resistance.

To improve they ad an electrolyte gel and cal them Lithium-Ion Polymer. Polymer cells have a flexible, foil-type housing; a metal shell is not necessary, and therefore they are much lighter in weight.

A LiPo cell has a thickness of less than a millimetre; the thinnest battery packs are only 4 mm thick. Thanks to their flexibility, they transform them in all shapes and sizes. Just like a Li-ion cell, a single LiPo cell emits a voltage of 3.7 volts.

This is in contrast to NiCd or NiMH cells that deliver 1.2 volts. A LiPo cell does not suffer from the memory effect. The energy density and the power density reach the highest values ​​of all types of batteries. And therefore exceptionally suited for off-grid solar systems.

This is partly due to the absence of a metal housing that counts typically heavily in the total weight. However, the production of LiPo batteries is more expensive than that of other cells.