Without question, lithium-iron batteries present some distinct advantages that other types of batteries don’t offer - but we still have lead acid batteries as the default in our kits.
The key factor in our decision is the price point - lithium batteries are about 4x the cost of lead acid. We've always tried to make off-grid solar an affordable option, and offering lead acid batteries allows us to do so. They are a proven reliable option, and still have a lifespan of at least 5 years when they're treated well.
As we've explained elsewhere, lithium batteries are a very good option for full time off-grid living - their added protections and longer lifespan do make them a more economical option in the long run. However, they are still a much higher up front cost that is out of reach to many customers.
Though we don’t currently provide lithium-iron batteries as standard in our kits, it is not something that we expect to avoid indefinitely. As technology improves and the cost of these batteries begin to level out, this is a product that we believe will be much more viable in our business, in the foreseeable future. For the time being, while lithium-iron batteries do have many distinct advantages over lead-acid, we don't believe this outweighs the current price difference, so will continue to offer lead-acid batteries by default until lithium-iron becomes the superior option.