top of page
9689338E-C691-4DC7-ABA3-05930D268CFA_edited.jpg
  • Writer's pictureJeff Mathias

Residential Battery Storage - what are my batteries made from?


Why You Should Care What Your Battery Is Made Of:

As home energy storage batteries continue to gain popularity, some look at how many kWh the batteries store (the gas tank), or the size of the inverter (the engine, or how noisy they are (the muffler). As I researched this blog, I realized the battery chemistry can be one of the biggest issues and it is often not even considered. The two primary lithium battery chemistries found in home energy storage systems are lithium nickel manganese cobalt oxide (NMC) and lithium iron phosphate (LiFePO or LFP). They both store power and allow it to be used when needed. So, what is the difference, and should it really matter to a homeowner? This blog will take a 10,000-foot view of these chemistries and look at issues of safety, longevity, best use cases, application use, and politics. If you want a deeper dive, there are scientific blogs on this topic on the internet.


Lithium Nickle Manganese Cobalt (NMC)


Lithium Nickle Manganese Cobalt (NMC) is a popular battery in electric cars, portable consumer electronics and home storage systems. So why make a battery with cobalt? It allows for lighter weight batteries and increases the power of the battery which is great for portable electronics and electric cars. While NMC provides a safer fuel than gasoline or diesel, the downside of adding cobalt is that it is very combustible and reports of NMC batteries going into “thermal runaway” is becoming common news. These NMC fires are hot and virtually cannot be extinguished. Many fire organizations are advising fire fighters to just let these extremely toxic fires burn themselves out. Even if fire fighters are successful in stopping the initial fire, often these batteries reignite, causing even more damage.


Are my concerns around the safety issues of cobalt unfounded? Remember the hoverboard, laptop and galaxy phone fires? These were all caused by cobalt going into thermal runaway. Anytime you travel by air, you are told you cannot check lithium batteries in luggage, and fireproof containers are now common place in the cabin so batteries that catch fire can be contained. A federal probe has just been launched into why Tesla cars are catching fire while sitting on the street (no accident involved). I am a SCUBA diver and two of the boats I have dove from, The Conception from Santa Barbara and The Red Sea Aggressor recently had fires killing 35 people with lithium cobalt batteries being the leading theories as to the cause. I recently dove on sister ships of these boats policies no longer allow unsupervised overnight charging of batteries.


When I was installing systems, we didn't install NMC batteries as we believe even one fire caused by installations of our systems would be one to many. All manufacturers are trying to remove cobalt from their batteries to increase safety and lower cost, but it is not an easy process and could take a decade to accomplish. The engineering challenge is that reducing the cobalt content reduces the life cycle in the cells and with many home storage companies offering up to 10-year warranties, this is an issue. Also, as you decrease cobalt and replace it with nickel, heat increases, which, if not cooled, can lead to combustion. Some NMC batteries have cooling systems in them to counter the heat created by the nickel and these fans and pumps increase the noise the storage systems produce. Also, with very few moving parts in a storage system, fans and pumps add moving parts which are more likely to fail.


Another more political issue is that 60% of cobalt comes from the National Republic of the Congo. It is often mined by children and women in hand dug mines, without any environmental or humanitarian oversight. These "miners" are being exposed to toxic materials and extremely unsafe working environments. Also It is thought that by 2022 demand will outstrip supply of cobalt so this very expensive element will most likely continue to increase in cost.


Lithium Iron Phosphate


Lithium Iron Phosphate (LiFePO or LFP) batteries are much safer than NMC batteries and often have twice the useful life . There are many tests on the internet that show an NMC battery being drilled or crushed and exploding where the LFP batteries under the same conditions just fizzle. LFP is heavier, which is a significant difference in electric cars and portable electronics, but not a very big disadvantage in the home storage market. LFP also produces more energy but at the expense of power (going 0-60), so again not ideal in electric cars but perfect for home storage


The benefits of choosing LFP batteries to store your solar energy in your home include:

  • Fire safety (my battery is installed in my laundry room)

  • Almost double the longevity over NMC batteries

  • Produces less heat which works better in hot climates

  • Does not require as much cooling or venting and thus can be up to 50% quieter in home storage

  • Not toxic when burned (burned NMC creates toxic superfund sites)

  • Offers a non-toxic environmentally benign battery

This battery does not have all the negative headlines as its NMC brother. It does not catch fire, it has not caused deaths, it is not under federal probes, it is not toxic, and mining the products to build LFP is one of the least invasive in the mining industry.

In summary I believe that using LFP batteries was in line with our philosophy as a solar and storage installer. and now my philosophy as a consultant. We want to provide our homeowners with the safest, longest lasting technology available and a healthy environment for all, leaving this planet better than we found it.

4 views0 comments

Comments


bottom of page