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Lithium-Ion Batteries

There are many “flavors” of Lithium batteries, each with their respective benefits. You’ve probably heard of lithium batteries catching on fire – well, LFP (Lithium Iron Phosphate, LiFePO4) is not one of those! Even during puncture tests when large currents would lead to local hotspots, the relatively high thermal runaway temperature of 518F is unlikely to be reached. If this temperature is reached, the active ingredients of LFP are inert enough to keep catastrophe at bay. There are trade-offs between safety and performance – if you’re willing to accept the slightly lower energy density (than Lithium Cobalt Oxide, LiCoO2 for example) in exchange for safety, LFP is a natural choice. Even this lower density variety of lithium has about 2.5x the energy density of lead-acid.

At first these batteries may seem quite expensive, but when you consider the life expectancy (up to 10,000 cycles!) and other advantages, this view begins to change. They have no memory problem – there’s no need to exercise (periodic discharge) them, or charge them fully as is the case with lead acid. There is no additional cost for sealed format – LFP cells are sealed and can be installed in a living space, and in any orientation. Their high efficiency means you get out most of what you put in, and battery heating is minimal.

Aside from the initial cost, the major disadvantages of lithium-ion batteries are the same as other batteries – low performance at freezing temperatures, and damage if operated above maximum or below minimum parameters. SimpliPhi Smart-Tech series has implemented a real-time equalization circuit – the weaker cells are dynamically cared for so they’re not overstressed. This in combination with the solid-state protection circuit makes for a highly reliable and effective energy storage system.

Budget approx. $1.20/Wh for small systems, or as little as $1/Wh for large systems.

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"In recent years, battery technology, specifically lithium-ion batteries, has seen increasingly rapid development, spurred by the growth in the electric vehicle (EV) market."

Solar Living Sourcebook 14th Edition
Chapter 3: Sunshine to Electricity

Lithium-Ion Batteries from Real Goods