Comparing Lithium-Ion Batteries with Deep Cycle Lead-Acid Batteries for Home Energy Storage
Posted on August 16 2016
On our previous articles, we have covered the usage of batteries to power our houses, how it might be the future of household electricity, and how it may benefit us in the long run.
While Tesla recently brought batteries to mainstream popularity with their announcement of the Powerwall back in 2015, actually, home batteries have been around for a while and have been one of the most important equipment for renewable energy enthusiasts and practitioners.
The difference is, solar battery banks popular in the renewable energy community is typically made with deep cycle lead acid technology, while the Tesla Powerwall uses lithium-Ion Technology. Quite possibly the ones we have from big players like Samsung, Panasonic, LG, and Schneider Electric will also use lithium-Ion.
With the big companies moving towards lithium-Ion, does it have a surefire advantage over the Lead-cycle? Well, yes and no. Both have their own advantages, as well as disadvantages. This article will attempt to cover the differences between the two, and you'll be the judge which one is the better bet.
Let's start with an overview of their differences.
There are more differences than similarities between the two battery technologies, and here are the most notable ones:
- Weight: Lithium-ion batteries typically weigh 30% lighter than lead-acid batteries.
- Discharge: Lithium-ion battery reached almost 100% charge and discharge, with even the worst, have 80% of efficiency. On the other hand, Deep-cycle lead acid batteries typically have less than 80% charge-discharge efficiency, and can range from 50% to 95%.
- Cycle Lifetime: The best of Li-ion batteries can last 5,000 cycles, with the average being 2,000-4,000 cycles. Lead acid batteries have an average cycle of 400-1,500.
- Voltage Stability: Li-ion batteries are almost 100% stable in term of voltage, while in deep-cycle lead acid batteries, the voltage will constantly drop over its discharge (sloping voltage.)
- Cost: Lead-acid batteries are one of the cheapest batteries available on the market, both in its initial cost as well as cost per kWh. On the other hand, Li-ion is one of the most expensive.
- Environmental Impact: The lead content, as well as the electrolytes in lead-acid batteries, can damage the environment. Li-ion technology is much cleaner and safer for the environment.
Now that we've covered the overview of differences between the two, we will dig dipper into one of the most important qualities of batteries: the charging time.
Charging Time Comparison
Charging time is one of the qualities where lithium-ion batteries truly shine. Li-ion batteries have 10 times faster charging time compared to lead-acid batteries.
This is mainly caused because lead-acid can only handle charge rate of around 0.2C (0.2 times its capacity), meaning for a 500 Ampere battery, we can only charge it with a 100 A current. More than that and the battery will overheat, slowing down the charge time further.
Li-ion, on the other hand, can handle charging 5 times its capacity, with the recommended being 0.5C. Meaning, on the same 500 Ampere battery, it can handle 250 Ampere charging current.
However, Li-ion can't handle overcharging (keep being charged when the capacity is already full), while lead-acid batteries can handle overcharging perfectly, forming Hydrogen gas from its excess capacity.
This situation requires a protection circuitry to be included in a Li-ion battery to control overcharging, overvoltage, and its discharge which needs to be custom made and increase its already expensive cost further.
With that being said, Li-ion is a clear winner in term of charging time efficiency. Moving on, let's discuss its cycle lifetime.
Life Cycle Comparison
Although the life cycle of batteries will depend on how you use it, temperatures, and many other factors, current Lithium-ion batteries have an average lifetime expectation of 2,000-4,000 cycles, compared to 400-1,500 cycles of lead-acid batteries.
The term 'cycle' refers to a period of charge and discharge, with one cycle being one time you fully discharge a fully charged battery.
Again, Li-ion is another clear winner, and the need to replace lithium-ion batteries will be far less than of lead-acid batteries.
Can you guess this one? Yes, Lithium-ion is another winner this round, but not without a catch. In general, both lithium and lead acid are harmful material, both to the human body and to the environment.
Technology then allows the ionization oh lithium, creating the safer lithium-ion, at the sacrifice of energy density. But it's not without fault; there have been cases of Li-ion batteries catching fire and exploding by itself, such as the famous accidents of hoverboards just in 2015, as well as similar cases with cellphones and notebooks.
Battery University discussed in great details about the safety concern over Li-ion batteries. Their conclusion: the heat-related accidents are rare, and most Li-ion batteries are equipped with three layers of safety measures: the limitation of the Lithium-ion in a safety level, various safety mechanisms within the cell, and electronic protection circuit.
On the other hand, deep cycle lead-acid batteries produce hydrogen when being overcharged, and continuously produces electrolytes. Not to mention, the lead acid itself is a very dangerous substance. However, they are also equipped with safety mechanisms to reduce the risks.
Arguably in its purest form, Li-ion battery is more harmful. However, various technology and safety mechanism are employed, increasing its safety to be one of the safest battery choices in the market. The catch? Those safety measures contribute to our next discussion: price.
After we went through all the comparisons, this is almost an obvious guess. Lithium-ion battery is indeed the more expensive option with its noticeable advantages.
Li-ion batteries have an average cost per cell of $300-400, although General Motors claims it's closer to $145 now. Lead-acid batteries, on the other hand, have an average cell cost of only $90.
Economist and technology practitioners seem to agree that the price will continue to decrease for the next 5 years, especially with Tesla building their gigafactory with the aim of decreasing their Powerwall cell cost to less than $100.
Conclusion: Comparing in Conjunction With Home Electricity Applications
After we've learned about all the differences the two options have, we can come to a conclusion: Lithium-ion is indeed a better option, but with more expensive cost.
So when considering both as an option for your home energy storage, it's no more the question of advantages and disadvantages, but the question of: Will it be worth it?
To answer that, let's step back and review the notable advantages of Li-ion again:
- Weight: Weight is clearly an important advantage for Li-ion in applications like cell phones and notebooks, which require mobility. However, in home energy storage application, it's not a determining factor, since your battery will be mounted on a wall excepting special cases.
- Charging Time: You will be using an unlimited energy of sunlight or wind as your energy resource, and you have all the time in the world provided that your solar or wind system is designed properly. Excepting you live in an extremely harsh condition, lead-acid batteries can still be sufficient.
- Safety and Environmentally Friendly: When dealt correctly, lead-acid batteries can also be perfectly safe for human. For environments, however, the cleaner energy of Li-ion might be worth it, depending on your stance on environmental impacts.
- Lifetime Cycles: The cost of buying two lead-acid batteries can still be cheaper than one Lithium-ion battery. So, replacing a lead-acid battery is still a viable option than investing in a Lithium-ion battery.
There's another advantage you might consider, though: simplicity and luxury.
Coming from big companies like Tesla, and shortly Panasonic, LG, Schneider Electric, Samsung, and probably many others, investing on a Lithium-Ion home battery will provide the sense of security and luxury with its warranty and after-service from certified technicians.
Is it worth the money? We'll let you be the judge.