Why are they so expensive?

The upfront cost of our lithium deep cycle battery is higher than a lead acid equivalent. But when you divide that cost of the life of the battery, our LIFEPO4 battery is already cheaper than a lead acid battery. When you factor in the cost and time associated with changing the batteries, you really save a bundle when you decide to install a Battle Born battery bank. At 3000 cycles most people will have these batteries for 10 to 15 years.