Most of the batteries on the market are LiPO based. These are really good for mobile applications as they are very energy dense. This makes them light when you are paying to move them.
Battery installations on a house are not mobile so energy density is not as high a priority. There are other properties which should be considered when making this investment.
- Battery stability and safety
- Internal impedance of battery
- Discharge level
- Battery longevity
- Expansion options
My original battery set were Lead Acid Gel Cells. This was really the only option that was affordable back in 2013. They had many drawbacks. Namely they had a life expectancy of 8 to 12 years (I only got 6.5 years, just out of warranty) and they do not like discharges below 60% of capacity. One cell failed and that meant the whole bank was not serviceable.
I was looking at a Nickel Iron system. While they are almost bullet proof and can be deep cycled they can have a high impedance when cold. That usually becomes evident when you put on the kettle and/or toaster on a cold morning. I did explore the LiPO offerings too. Although it is rare I did not like the idea of a cell having a thermal runaway as they are almost impossible to extinguish. The other downside is to service life, which is not much better than Lead Acid.
The system I purchased was LTO Batteries (lithium-titanium-oxide) which have many advantages of LiPO for static installations. They are very stable and have no risk of thermal runaway. They can tolerate deep discharge without damage. They have very low internal impedance and can deliver high power and fast charging. They also have a very long life, my system has a 20 year (or 22,000 cycles) warranty that they will be 90% of original capacity. They have an expected life of 50+ years. I can also add extra capacity at any time I have available funds. I currently have 4 units @ 1.93kWh but I would like to add two more.
The longevity of these units mean it has an excellent payback on investment.
My connection fee to the Grid is about $1.76 a day. Due to these batteries and my FiT my latest quarterly bill is under $47. That is because I use very little supply from the grid and export a lot. These are really good batteries and they do not smell of Musk.
