Lithium vs Alkaline Batteries for Solar: A Detailed Comparison

Lithium and alkaline batteries store and provide power for solar lights, gardens, outdoor solar lighting, and off-grid solar systems. However, they have very different compositions and characteristics, making each better suited for certain uses.

In this article, we will compare alkaline and lithium batteries in-depth, looking at aspects like construction, voltage, capacity, performance, cost, and more. We’ll also overview the different types of lithium and alkaline batteries available and discuss when to use each type for solar applications.

Read on to learn which battery technology is right for your solar needs!

How Lithium Batteries Work

Lithium batteries derive their name from using lithium metal or lithium ions as the key component of their chemistry.

There are two main types of lithium batteries:

• Lithium Metal Batteries – These use lithium metal as the anode material. They offer high energy density but can pose safety risks. Lithium thionyl chloride (LiSOCl2) batteries are a common lithium metal type used in solar garden lights.
• Lithium-Ion Batteries – Unlike lithium metal batteries, a lithium-ion battery does not contain metallic lithium. Rather, they use compounds like lithium-cobalt-oxide (LiCoO2) or lithium-iron-phosphate (LiFePO4) as cathode materials. The anode is made of graphitic carbon. Lithium ions shuttle between the anode and cathode through a liquid electrolyte to generate power.

Some advantages of lithium-ion batteries over traditional lithium metal batteries include better safety, higher energy density, lower self-discharge, and lack of memory effect.

As a result, lithium-ion has become the dominant lithium battery chemistry for most consumer electronics.

How Alkaline Batteries Work

Alkaline batteries derive their name from using an alkaline electrolyte, typically potassium hydroxide. The positive electrode comprises manganese dioxide, while the negative electrode is made of zinc.

The battery generates power electrochemically by the reaction between the zinc anode and the manganese cathode. The alkaline electrolyte facilitates ion conduction to keep the reaction going.

Compared to lithium batteries, alkaline batteries offer simplicity and low cost. However, they tend to have lower energy density. While rechargeable alkaline batteries exist, most are intended for single use.

Key Differences between Lithium and Alkaline Batteries

Now that we’ve looked at how lithium and alkaline batteries work, let’s explore some of the key differences between the two technologies:

Construction and Chemistry

As described above, the core chemistry and materials that make up lithium vs. alkaline batteries are quite different:

• Lithium batteries use lithium metal or lithium compounds as the central component. Different types employ various lithium-containing cathodes.
• Alkaline batteries rely on manganese dioxide as the cathode and zinc as the anode, with an alkaline electrolyte.

This contrast in construction and composition leads to major performance differences.

Voltage

• Lithium batteries generate higher voltage than alkaline. A single lithium cell provides 3.6-3.7V, compared to just 1.5V for an alkaline cell.
• Higher nominal voltage enables lithium batteries to better support solar systems with higher power needs. Lithium’s voltage also stays more constant as the battery discharges.
• With lithium batteries, connecting cells in series readily allows the creation of higher voltage battery packs like 14.4V or 72V. This is not practical with alkaline batteries.

Energy Density

• Lithium batteries have much higher energy density, on the order of 100-265 Wh/kg, compared to just 30-80 Wh/kg for alkaline.
• This allows lithium batteries to store energy in a given size and weight. Lithium’s high energy density is crucial for portable solar lights and devices.
• A lithium battery can be much lighter than an equivalent alkaline battery for the same capacity. Weight savings are important for mobile solar applications.

Rechargeability

• Alkaline batteries are intended for single use and cannot be recharged. Attempting to recharge an alkaline battery is dangerous.
• Lithium batteries are designed to be recharged hundreds of times. Lithium-ion rechargeable batteries used in solar energy storage typically last for 2000-5000 cycles.
• Rechargeability makes lithium batteries much more cost-effective for long-term solar power usage. Alkaline batteries must be replaced frequently.

Cost

• Alkaline batteries are generally much cheaper upfront to purchase by a factor of about 3-4x per battery.
• However, the fact that alkaline batteries cannot be recharged means they have higher lifetime costs for solar usage.
• Lithium batteries have higher upfront costs but save long-term money thanks to rechargeability. Overall lifetime costs are lower.

Performance

• Lithium batteries hold their voltage and capacity better as they discharge. Alkaline batteries tend to fade in performance.
• A lithium-ion battery maintains performance at high discharge rates and currents better than alkaline.
• Lithium batteries perform better at temperature extremes, both hot and cold conditions. Alkaline batteries quickly lose power at temperature extremes.
• The superior performance of lithium batteries makes them better suited for solar devices. Alkaline works better for low-drain uses.

Self-discharge

• Lithium batteries have lower self-discharge rates, typically losing 5-10% of their monthly capacity when stored.
• Alkaline batteries have relatively high self-discharge, losing 20% or more of their monthly capacity. This shortens shelf life.
• Slow self-discharge helps lithium batteries hold a charge for longer when storing solar energy.

Memory Effect

• Alkaline batteries can suffer from memory effects — if recharged before fully discharged, their capacity decreases over time.
• Lithium-ion batteries do not demonstrate any memory effect. They can be charged at any point without capacity loss.

Types of Lithium Batteries for Solar Applications

There are several specific lithium battery chemistries used in solar applications:

• Lithium Cobalt Oxide (LiCoO2) – Offers high energy density but can be unsafe if damaged. Used in some solar devices.
• Lithium Iron Phosphate (LiFePO4) – Lower energy density but very safe and stable with excellent cycle life. Ideal for solar energy storage.
• Lithium Titanate (LTO) – Fast charging capability makes it suitable for some solar installations.
• Lithium Nickel Manganese Cobalt Oxide (NMC) – Good high capacity and safety balance. Used in some home solar battery setups.

LiFePO4 is generally the preferred lithium battery chemistry for residential solar energy storage needs.

Types of Alkaline Batteries for Solar Applications

There are two main classes of alkaline batteries used in solar applications:

• Primary Alkaline – Single-use, non-rechargeable alkaline batteries are commonly used in lower-drain solar lights and devices. Sizes include AAA, AA, C, D, and 9V.
• Secondary Alkaline – Rechargeable NiMH alkaline batteries are also viable for some solar products. Common rechargeable sizes include AAA and AA.

Primary alkaline batteries are the cheapest but least long-lasting option for most solar usages. Rechargeable lithium-ion tends to be better for solar energy storage overall.

Lithium or Alkaline Batteries for Solar: Which Is Better?

So when should you choose lithium vs. alkaline batteries for solar applications? Here are some guidelines:

Lithium Batteries Are Better For

• Solar devices with high power demands – Lithium works better for high-drain uses.
• Applications where small size and weight matter, like portable solar lights – Lithium batteries are lighter weight.
• Solar energy storage where frequent recharging is required – Alkaline batteries can’t be recharged.
• Very hot or cold weather – Alkaline batteries lose power quickly in extreme temps.
• Mission-critical outdoor solar installations – Lithium batteries give more reliable, stable output.

Alkaline Batteries Are Better For

• Low-power solar devices like solar path lights – Alkaline provides a more economical choice.
• Cost-sensitive applications where frequent battery replacement is acceptable.
• Solar devices where size and weight are not important considerations.
• Warm weather climates – Alkaline functions better than lithium at high temperatures.
• Non-critical solar installations where some variability in performance is allowable.

For many everyday uses, both lithium and alkaline can serve the purpose. However, evaluate the performance, cost, and usage factors that matter most for choosing the optimal battery type.

How to Tell If a Battery Is Lithium or Alkaline

For small consumer batteries like AAs and AAAs, it can be tricky to know whether you have lithium or alkaline.

Here are a few ways to tell lithium primary batteries apart from alkaline primary batteries:

• Look for the Text on the Battery Label – It will typically indicate lithium or alkaline. Keyword clues are “lithium”, “Li”, or “Li-ion” for lithium batteries. “Alkaline” is normally printed on alkaline batteries.
• Compare Weights – Lithium batteries are lighter than alkaline. For example, an AA lithium cell may weigh around 15g vs. 23g for a typical alkaline AA. Similarly, an AAA lithium battery weighs around 7.5g vs. 11.5g for an AAA-size alkaline battery.
• Measure Voltage – An unused alkaline battery will be around 1.5V, while lithium AAs are usually 1.7-1.8V when fresh.
• Check Markings – A “L91” or “L92” marking indicates lithium AA batteries or AAA lithium batteries, also known as primary lithium batteries. On the other hand, alkaline batteries are often marked “LR6” or “LR03”.
• Consider Shape and Size – Lithium primaries often have a larger diameter than traditional AAs and AAAs. The ends are also usually flatter compared to alkaline batteries.
• Review Applications – Lithium primary batteries are popular in devices like digital cameras that benefit from lightweight batteries with slow discharge. Alkaline batteries tend to be used in simpler household electronics.

If unsure, consult your device manual or battery retailer for the recommended type. Using the wrong battery can damage electronics if the voltage levels are incompatible.

Frequently Asked Questions about Lithium vs. Alkaline Batteries

Can Lithium and Alkaline Batteries Be Used Together in Solar Devices?

In general, using lithium and alkaline batteries is not recommended. Their different voltages and discharge characteristics can lead to unreliable performance or safety issues.

Solar devices are normally designed for one battery type. An exception may be small coin cell batteries, where mixing might be acceptable.

How Long Do Lithium Batteries Last in Solar Applications?

Properly maintained lithium-ion batteries in solar energy storage typically last 5-10 years or longer.

Key factors impacting lithium battery lifespan for solar include battery quality, operating temperature, charge/discharge cycles, and depth of discharge. High temperatures, in particular, reduce lithium battery life.

Why Are Lithium Batteries Better for Solar Lights?

Lithium batteries are lighter, store more energy, and operate in cold better than alkaline batteries. Lithium batteries also recharge with solar panels much more efficiently.

These advantages make lithium batteries the top choice for powering most outdoor solar lighting.

Can You Use Rechargeable Alkaline Batteries in Solar Lights?

While possible, rechargeable alkaline batteries have limitations like low cycle counts that make them a poor choice for solar lights recharged daily.

Most solar path lights are designed for lithium-ion batteries that can handle frequent recharging. Using rechargeable alkaline batteries in solar lights will likely lead to a short lifespan.

Why Are Lithium Batteries Banned on Flights?

If damaged, li-metal and Li-ion batteries pose fire risks, which can be especially hazardous in aircraft cargo holds.

For safety, airlines and agencies restrict transporting lithium batteries on passenger flights, though some small lithium batteries are permitted in carry-on luggage.

Regulations continue to evolve to balance safety with the prevalence of lithium batteries.

Can You Bring Alkaline Batteries on Planes?

Standard alkaline batteries are permitted in carry-on and checked luggage on commercial flights without hazardous materials restrictions.

Being non-rechargeable and not using flammable lithium metal, alkaline batteries do not pose the same risks as lithium batteries in cargo hold. Just ensure any battery terminals are protected against short circuits.

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