5 years ago I created a series of how-to videos for a DIY solar generator. It has had a lot of traffic and is one of the most watched solar generator videos on YouTube. It has also had a lot of requests for a Lithium-ion version. Today we show you how to upgrade its battery bank to Lithium (LifePO4).
What are the advantages to Lithium Batteries?
There are several. First they can pack much more energy density in the same amount of space as well as significant weight savings. For example the Optima 12v lead cell / AGM battery with 55 amp hour capacity that we originally used in the build weighs 44 lbs. We are replacing it with a 12V LifePO4 battery of similar physical size, but it has a capacity of 100 amp hours, and only weighs 23 lbs!
Lithium batteries also can have much longer life. The one we are using today boasts a 10 year life span. Like all batteries though, the life can be shortened if it is over discharged or abused.
What is a BMS (Battery Management System)?
Many of the newer Lithium batteries comes with a built-in BMS system. This stands for Battery Management System and is built in circuitry to protect the battery from conditions that could shorten its life, or even pose fire / safety risks.
Because Lithium batteries have a higher energy density, they also have more requirements to keep the cells happy. They cannot be over charged like older technology batteries. In the past you needed to make sure everything connected to the battery was designed for lithium batteries, and would not overcharge it, over draw on current, run the battery too low, or it would risk damage to the battery or even increase the chance of a fire. The BMS system in newer batteries handles all that for us, so that they can now safely be used as a drop-in replacement in standard 12 volt systems.
Is a Lithium Solar Generator Better?
It terms of battery performance and portability, then yes, lithium batteries out perform the older technology used in lead acid based batteries. However there is a trade-off in cost. Lithium batteries still cost more than lead acid batteries, but the price difference is much less than it was ever a few years ago.
Do you need lithium batteries for solar power?
Whether you need to go with lithium battery technology for your solar generator is based on your needs. If you are building a large battery bank that does not need to be mobile, and you are not concerned about space or weight, you can still get more total amp hours per dollar with lead acid batteries. However when you factor in life expectancy of the batteries and other factors the argument for going with a lithium battery bank is getting stronger all the time.
How long does a lithium generator last?
Like most products, the useable life varies on a lot of factors. One of the biggest advantages to building your own solar generator is that can now easily replace any of the individual components when necessary. Solar panels are usually rated for a life of around 10 years. They can actually last longer, but the efficiency drops over time. A typical 10 year rated solar panel will be at or below 80 percent of its original efficiency after 10 years. Batteries are often rated in both years as well as charge cycles. However the total number of charge cycles will go down with deeper discharges of the battery. There are a lot of variables!