Lithium Batteries

Why Are Lithium Iron Phosphate Batteries the Best Solar Batteries?

To understand why lithium iron phosphate batteries have become the new gold standard for renewable energy systems, it’s helpful to compare them to the previous standard battery type for these applications - lead acid.

Compared to lead acid, lithium solar batteries are:

• Deeper cycling - tolerant of 80-100% depth of discharge (DoD) compared to 50%, giving you access to more of their nameplate amp-hour or Watt-hour capacity.
• Longer lasting - featuring a cycle life of 5000 to 10,000+ cycles compared to approximately 3000 cycles.
• Lower in lifetime cost - with deeper cycles and more of them, the cost per kWh cycle of lithium iron phosphate batteries is unmatched.
• Maintenance free - no watering, equalizing, or cleaning corroded terminals.
• Tolerant of lower ambient temperatures without capacity being affected. There are even some models from KiloVault rated for sub-freezing temperatures.
• Safe and nontoxic - with no off-gassing or thermal runaway issues, they can be installed indoors - further reducing temperature-related capacity concerns in cold weather months.
• Lightweight - easier to ship, move, and install.
• Equipped with built-in BMS - most lithium solar batteries have an integrated battery management system (BMS) that monitors state of charge (SoC) and protects the cells from voltage, current, and temperature hazards.

It’s also helpful to compare lithium iron phosphate batteries to an alternative type of lithium ion batteries for solar and renewable energy systems - lithium nickel manganese cobalt (NMC).

Compared to NMC, lithium iron phosphate batteries are:

• Longer lasting - with less cell degradation when cycling deeply (80-100%).
• Safer and thermally stable - LiFePO4 cells have a significantly higher temperature threshold for thermal runaway (and fires). Internal heat generated from charging and discharging stays safely below this threshold at all times.
• Less expensive - NMC cells are a relatively new technology and require more heat dissipation elements in their architecture.
• Wider operating temperature range - offers more options for installation location.

Best Applications for Lithium Solar Batteries

It should be clear by now that lithium batteries for solar energy storage are superior to lead acid batteries in every way except for the higher upfront cost (though when it comes to lifetime cost per kWh cycle, lead acid can’t touch them). Here are some specific applications where lithium solar batteries really excel and why:

• Full-time off-grid homes benefit from the ability to do truly deep, daily cycling with a long cycle life for years and years of reliable power.
• Part-time off-grid residences like vacation homes benefit from the lack of maintenance needed to keep the batteries working well despite infrequent use and the ability to install them inside the house to keep them protected.
• Remote cabins and equipment benefit from their light weight, relative portability, and wide ambient temperature range.
• Emergency backup power for grid tied solar systems benefit from the high DoD, which keeps the number of batteries needed to power critical loads at a minimum.

Lithium Solar Battery Chemistry

Under the umbrella of "lithium batteries", there are both lithium metal batteries and lithium ion batteries. Lithium metal batteries are not rechargeable, so they’re not relevant for solar power systems.

Under the umbrella of "lithium ion batteries", there are several types - each with its own set of pros, cons, and specific use cases. Today, three types are by far the most common, and they have different specialties:

• Lithium iron phosphate (or LiFePO4 or LFP) - built for long cycle life, tolerance of deep discharging, and thermal and chemical stability for safety. LiFePO4 cells make the best batteries for solar and other renewable energy systems.
• Lithium nickel manganese cobalt (NMC) - built for improved energy density(Watt-hours / weight) and low self-discharging. NMC cells can handle higher charging rates than LiFePO4 cells, but at the risk of thermal runaway. They are commonly used in electric vehicles and battery-powered tools.
• Lithium cobalt oxide (or LiCoO2 or LCO) - built for extreme energy density, but relatively short-lived and also prone to thermal runaway - sometimes to dangerous levels. LCO cells’ best and most common application is in portable devices like phones and laptops.

Questions about lithium solar batteries or alternative deep cycle batteries? Give an altE solar expert a call today at 877-878-4060.