Here goes nothing! After a lot of planning, and several revisions, it’s happening. I’ve started the process of replacing an aged house battery bank and inverter/charger with a new system based around lithium battery technology.
This isn’t going to be a simple remove-and-replace project though. While there are a number of commercial offerings already available using prismatic lithium iron phosphate cells (LiFePO4, sometimes abbreviated LFP), often packaged with a battery monitoring system of some sort, we’re going to look to a much cheaper source of batteries, and a system design that should yield far better performance in the long run.
Typical LFP batteries run in the neighborhood of $1 per usable Watt-hour. We’re going to be using a battery pack from a wrecked 2012 Chevrolet Volt as the starting point for this system–prices vary, but I’d estimate they’re out there for an average of $2100 or so. That gets a pack with 12kWh of usable energy, or about $0.18 per Watt-hour. That means that if we’re intending to use the full Volt battery pack that we’re saving about $10,000 just on cell cost.
This is a big project, and I’m going to be breaking down the design process into a bunch of separate posts. But we’ll end up with a power system with energy storage equivalent to 24 golf cart batteries with about 80% weight savings, and less total cost than even a conventional lead acid setup (at 50% depth-of-discharge, we’re looking at 0.5kWh each). We’re also going to be able to run some big loads (like air conditioners) without straining the system. Stay tuned!