The lithium-ion family of batteries have particular advantages for Off-Grid alternative energy storage (particularly the type with a iron-phosphate cathode) . They’re available from Iron Edison, located in Denver, Colorado – who serve the alternative energy community with a wide range of products.
One of their specialties is battery energy storage. I have been excited about their latest technology Off-Grid battery system. It’s a type of lithium-ion battery, but with iron as the cathode. Also referred to as lithium-iron, or lithium-iron-phosphate. There are many advantages in my view.
Advantages of Lithium-ion Batteries
Lead acid batteries are made from a mixture of lead plates and sulfuric acid. This was the first type of rechargeable battery invented back in 1859.
On the other hand, lithium-ion batteries are a much newer invention. They have only been around, commercially speaking, since the 1980s.
Lithium technology has become well proven in small power electronics such as laptops or wireless tools, and has become progressively common in these applications – coming out of the older chemical composition of the NiCad rechargeable battery (nickel-cadmium) due to the many advantages of lithium.
But, you may recall the many stories from a few years ago about the batteries of defective laptops bursting into flames. The lithium-ion batteries also gained a reputation for catching fire in a dramatic fashion. The formulation of the commonly used lithium-ion battery had been LiCoO2 (lithium-cobalt-oxide), and this battery chemical composition is prone to thermal leakage if the battery is accidentally overcharged.
Lithium Iron Phosphate
However a new formula of lithium-ion batteries was developed, called lithium-iron-phosphate. Known as LiFePO4 or LFP, these batteries have a slightly lower energy density but are intrinsically incombustible. They are much safer than those of lithium-cobalt-oxide. Once you consider the advantages, lithium-iron batteries become extremely tempting.
Difference Between Lithium-ion (cobalt) and Lithium-ion (iron)
Similar technologies, but there’s a difference. There are different types of lithium-ion batteries, each with their own characteristics.
A Lithium-ion battery is a rechargeable battery, most common with cobalt-oxide as a cathode. The newer lithium-iron battery is also a rechargeable type of battery within the lithium-ion family. But it’s made with iron-phosphate as the cathode material.
So what’s the real-world difference? I read the following while searching on this subject:
Phosphate based technology possesses superior thermal and chemical stability. This provides better safety characteristics than those of lithium-ion technology made with other cathode materials.
Lithium phosphate cells are incombustible in the event of mishandling during charge or discharge. They are more stable under overcharge or short circuit conditions and they can withstand high temperatures without decomposing.
When abuse does occur, the phosphate based cathode material will not burn and is not prone to thermal runaway. Phosphate chemistry also offers a longer cycle life.
The following is a summary of eight distinct advantages as described by the Iron Edison Design Team.
1. Superior “usable” capacity
Unlike lead acid batteries, it is considered practical to regularly use 90% of the nominal capacity of a lithium-ion battery bank, and occasionally more. Consider a 100 A hour battery – if it were lead acid it could only be used 30 to 50 A hour capacity. But with the LFP lithium you could take 90 A hour or even 100 A hour (100% DoD or depth of discharge) .
2. Superior Life Cycles
The experimental results indicate that it could expect from 3,000 to 10,000 life cycles for a bank of lithium-iron phosphate batteries. Both, the C ratio and the depth of discharge (DoD) affect the expected useful life. Some recent measure shows that a LFP battery will deliver more than 80% of its capacity after 3,000 cycles at 100% DoD (depth of discharge) or even 8,000 cycles at 65% DoD (depth of discharge). All these tests are made with cycles of 1C ratio, that is, with rates of charges – 1 hour downloads; If this rhythm or time is higher, the cycles increase markedly, reaching 20,000 cycles.
In contrast, even the best deep cycle lead acid batteries provide 250-1,200 cycles.
The drawing below shows the expected number of cycles for the lithium-iron-phosphate batteries.
3. Advantages of size and weight
Small footprint. From a practical perspective, the 4LiFe batteries are lightweight (about 1/2 the weight of lead acid). Check out IronEdison.com for specific size and weight dimensions.
4. Fast and efficient loading
Lithium-ion type batteries can be charged “quickly” at 100% capacity. Unlike lead acid, there is no need for the final phase of absorption to obtain 20% final storage. If your charger is powerful enough, lithium batteries can also be charged incredibly fast. If you can supply enough charging amps – you can actually fully charge a lithium-iron battery in just 30 minutes!
But even if you can not completely fill it to 100%, do not worry – unlike lead acid, this phenomenon does not damage the batteries.
This gives us a lot of flexibility when it comes to selecting energy sources without the need to worry about periodically making a full charge. Several days partially cloudy with your solar system? No problem. Charge what you can and do not worry about leaving the battery bank perpetually undercharged.
5. Very little energy wasted
Lead acid batteries are less efficient at storing energy than lithium-ion batteries. Lithium batteries charge at almost 100% efficiency, compared to the 85% efficiency of most lead acid batteries.
This can be especially important when you are charging via solar, when you are trying to get the maximum possible efficiency out of all the amps before the sun goes down or gets covered in clouds. With a limited roof this becomes very important when optimizing any power surface you can mount.
6. Climatic resistance
Lead acid and lithium batteries lose capacity in cold environments. Lithium-ion batteries are much more efficient at low temperatures. In addition, the discharge ratio affects the performance of lead acid batteries. At -20ºC, a lithium battery that delivers a current 1C, can deliver more than 80% of its energy when the lead acid battery will deliver 30% of its capacity. For harsh environments (heat or cold), lithium-ion is the appropriate technological solution.
7. Versatility in its location mode
Batteries do not need to be stored vertically, or in a ventilated battery compartment.
8. Zero maintenance requirements
These batteries are maintenance-free, in that a “rolling” process ensures that the cells in a battery bank are charged equally – automatically provided by the BMS (battery management system). Just charge the battery and you’re done.
~by Iron Edison Design Team
Iron Edison is an advertiser on this site. For those researching this type of battery storage for Off-Grid systems, I do recommend that you look into this technology as you go through the decision-making process.
Continue reading: New Lithium Iron Battery | Lower Cost of Ownership