Lithium Solar Batteries: The Nobel Prize-Winning Technology You Can Have in Your Home

Akira Yoshino developed the first lithium battery prototype in 1985. In 2019, they awarded Akira the Nobel Prize in Chemistry for the development of lithium-ion batteries.

Today lithium is the most promising battery chemistry. Used in everything from iPhones to Teslas, lithium batteries have the most energy density per weight, are safer to use and have longer lifespans.

The drop in price for lithium batteries has made them a popular option not just for mobiles and electric cars but for energy storage in solar power systems. The energy capacity per price dropped tenfold from 0.3 Wh per dollar to 3 Wh per dollar between 1991 and 2005.

Is lithium a good solar battery?

Lithium batteries are “smart batteries”. They are smart in the sense they have a built-in battery management system (BMS). The BMS regulates vital functions like charging and temperature to ensure the battery’s health.

While there are different chemistries of lithium batteries, lithium iron phosphate (LifePo4) is the one most popularly used for solar. Lithium iron phosphate has a better cycle count, longer shelf life and is safer.

Lithium batteries have a few more advantages over other batteries. They are, however, 2-3 times more expensive than lead-acid batteries.

Lithium battery specifications.
Lithium battery specifications.

If you’re looking into which solar batteries to buy there are several characteristics, you should know if you’re looking at lithium. These are battery capacity, energy density, efficiency and cycle life.

Battery capacity

Capacity is the total energy a battery holds. Batteries have a depth of discharge. Depth of discharge is how much energy (as a percentage of the batteries total capacity) can be used.

Lithium has a depth of discharge of 80% (90% in emergencies). That means if you have a 100Ah battery you can use 80Ah.

Lead-acid batteries, lithium’s closest competitor in terms of use in solar systems, have a depth of discharge of 50%. Depth of discharge is important to know because:

The depth of discharge for lithium solar batteries.
The depth of discharge for lithium solar batteries.

Efficiency

Lithium has an efficiency of 95%. Efficiency is how much of the battery’s stored energy you can use. If you have 100 watts coming into a lithium battery, you can use 95 watts.

Higher efficiency allows a battery to charge faster. This is especially important in winter or overcast days and you have an off-grid solar system.

Energy density

The density of a battery is how much energy per weight it holds. Lithium has a high energy density. This is partly because of its higher cell voltage (3.6V) compared to other solar batteries like lead-acid (2V).

A higher energy density makes lithium batteries up to 50% smaller and up to three times lighter than lead-acid. Lithium is also the lightest metal.

Being smaller and lighter allows you more flexibility in how you install them. You can fit them into smaller spaces and wall mount them, for example.

Here’s a detailed comparison of lead-acid vs lithium if you’re itching to know which is the better solar battery.

Cycle life

Batteries have a cycle life. A cycle is one charge and discharge (through use). Lithium batteries have an average of 5000 cycles. You can charge + discharge them 5000 times.

To work this out in days divide 5000 by 365. This gives lithium batteries a lifespan of up to 13 years. This is based on a one cycle per day basis and following the depth of discharge.

Other characteristics

Capacity, efficiency, density and cycle life are the key performance characteristics of a solar battery. There are a few others that aren’t as critical but are no less important. These are flexibility, battery maintenance, self-discharge and recycling.

Flexibility

With lithium, you can mix batteries of different ages. You can start with one battery this year then add more batteries when the need arises. This gives you the flexibility to build your solar system slowly.

Maintenance

Lithium batteries don’t need maintenance. This makes it easier to operate compared to some types of lead-acid batteries that need maintenance.

Self-discharge

Batteries lose some energy even when they’re not connected to a load. Lithium has a low rate of self-discharge (1.5-2%) per month so you don’t have to worry about the battery even if it goes months without being used.

Recycling

Because it has fewer toxic metals, lithium is categorized as non-hazardous waste. The iron, copper, nickel and cobalt used are considered safe for incinerators and landfills. This makes a lithium battery easier to recycle when it reaches its end of life.

Lithium solar batteries: The Pros and Cons

To summarize everything, let’s weigh up the pros and cons of lithium.

Pros of lithium batteries

  1. A deeper depth of discharge gives you more usable energy per charge.
  2. Faster charging. This is critical for winter and overcast days when there is limited solar energy to charge the batteries.
  3. A lighter and smaller battery that fits in tighter spaces.
  4. 10+ year lifespan.
  5. Zero maintenance battery.
  6. Better suited for high energy demand i.e., if you need a lot of energy to run many appliances.
  7. Flexible. You can start with fewer batteries and add more in the future.

Cons

  1. Expensive. The initial cost is up to 2-3 times compared to lead-acid.

When should you choose lithium batteries?

Lithium solar batteries have some standout qualities that make them a great solar battery. There are certain scenarios where the improved performance of lithium shines.

Off-Grid home or everyday use

For off-grid or full-time use, lithium gives you more energy. It can also handle more appliances. If your energy needs are high as in an off-grid home or business, lithium will give you the best performance.

Lithium battery FAQs

How much does a lithium battery cost?

Depending on size, lithium batteries cost anywhere from USD450 to USD2400 in Zimbabwe.

How long does a lithium battery last?

Lithium solar batteries last 10+ years when you stick to the recommended depth of discharge.

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