My name is Brian Betz and I’m a sales tech here at Backwoods Solar (BWS). I have worked for Backwoods Solar for 9 years and about a year ago I started researching different Lithium batteries. BWS had recently started selling the Discover LiFePo (Lithium Iron Phosphate) batteries and I was hoping to find a less expensive alternative to the excellent Discover AES models. In early July I put some “Eclipse” LiFePo batteries in my own off-grid home to give them a thorough test in my real-world application. The Eclipse battery is Chinese made but built to the specifications of myself and BWS. BWS is the sole distributor for these batteries and they are not offered through any other channels.
I have lived off-grid since 1995 in three different off-grid homes. My current home system consists of 2800 watts of solar split over two different arrays, with a Midnite Classic 250 and Schneider C40 for my charge controls. A Tristar 45 serves as my hydro diversion control. In the wet months of December through June I benefit from two micro-hydro turbines each producing about 175 watts from my small brook. During the darkest time of the year this is my main source of power, and July to November I’m “solar only” as the brook goes dry. I do occasionally need to use a gasoline backup generator for cloudy fall conditions before the hydro is running.
I thought with all of my off-grid experience I knew a lot about solar electric systems. It wasn’t until I started working at BWS that I realized how little I really knew. My greatest lack of knowledge dealt with the proper maintenance and care of lead batteries. Most of my off-grid experience has been with flooded lead acid batteries and my last set of T105 batteries lasted 7 years, with the constant winter/spring charging from the micro-hydro turbines greatly contributing to their longevity. And while I personally have never really had any problems with lead batteries, as I was taught to treat them gently and I was able to give them a lot of charging most of their lives, there is no question that lead batteries can be the most difficult part any off-grid system. Lead based batteries will have many uses for years to come, but At BWS I have spent countless hours teaching and helping my customers with their batteries. Lead batteries can be difficult to fully understand and I’d say it takes years for most folks to fully understand the ideal way to operate and maintain a lead-battery based system. It is with this background that I wanted to learn more about LiFePo batteries.
I have two Eclipse 48v-100ah batteries wired in parallel. They are mounted on the wall directly under my inverter/power center. Each has a display that shows volts, amps out, watts out and lifetime kWh. These basic batteries offer no communication beyond the simple meter on each battery, but I can watch the output of each battery and compare that to my inverter meter output as well has my Midnite Whiz Bang battery meter. They are simple to install and operate.
Being an active family household with several kids, we typically use 3-6 kWh daily. I purposely undersized the battery bank to give them a harder test. During the summer months it was common to fully charge the battery bank most every day, then see a discharge of 15% in the morning. As the days grew shorter the evening discharge grew larger, often up to 25%. When the clouds starting coming in the Fall, full charges were only occasionally happening. On about 10 occasions this year I let the battery bank go down to 30% state of charge (SOC) and over one period of 10 days, the SOC never went over 70%. This would have certainly caused problems with a lead battery bank. The LiFePo batteries charged like normal and never showed any signs of memory that can plague lead batteries in these conditions.
In short, my experience with these batteries has been wonderful. I am not nearly so mindful of power consumption in my household. I run the generator far less as I can allow longer, deeper discharges and can wait for a sunny day to put a charge back in the batteries. As I mentioned, I occasionally allow 70% discharge on the Eclipse batteries but I would never let my flooded batteries drop below 60%. I have no off-gassing to consider, no hydrometer readings to do and no water to add. The batteries take a fraction of the space of my old batteries and with them mounted on the wall I have more space in my mechanical room. The Eclipse batteries are easy – just charge them! I have had no complications with these two batteries wired in parallel and the only issue I’ve ever had was a battery shutdown due to over-voltage when I ran my generator too long. My old Schneider SW inverter needs a firmware update and the charging parameters are set a little too high for lithium batteries, causing the problem. After the generator was shut off and the battery voltage dropped, the batteries turned right back on.
Like most good things, lithium batteries do have some disadvantages. Don’t run LiFePo batteries to 0% SOC or you may need an external charger to “wake-up” a fully discharged battery. LiFePo batteries are more expensive initially, although they will likely be less expensive than lead over the life of the system. LiFePo batteries don’t charge below 32F and they don’t provide power output below 0F. They can be damaged below 0F so cold weather will rule these batteries out of many potential applications. However, if the battery can be held within the temperature constraints, I’m confident that many operators will really enjoy having a LiFePo (Discover or Eclipse) battery powering their system. And with the Eclipse battery’s claimed cycle life of up to 20 years (at shallow cycling) they make a great investment, especially if you figure in the saved generator run time and associated generator costs over those 20 years. My old beater generator may go another year or two now that it’s not running as often.
For more information about these batteries, you can email me at [email protected] or call 208-263-4290. All our sales techs are well schooled in LiFePo batteries and can answer most questions as well.