Do you want to buy new batteries? Exploring online forums and videos to get some valuable advice? If so, you must have seen a hot debate around AGM battery vs. lithium battery.
Battery selection has a direct impact on reliability, long-term costs, and overall performance. Whether you are installing a backup power system, running a solar setup, powering your 4WD, or upgrading your RV, AGM and lithium batteries stay relevant.
Both batteries perform well in different scenarios and for different applications, but choosing the wrong one may lead to unnecessary expenses and bad performance. This guide presents a comprehensive comparison between lithium and AGM batteries to help you choose the right one.
What Is AGM Battery?
The term “AGM” stands for Absorbed Glass Mat. The AGM battery belongs to the family of lead-acid batteries. It is sealed and built to achieve improved performance compared to conventional flooded lead-acid batteries.
This battery consists of a thin fiberglass mat inside its structure, which absorbs the electrolyte solution, making it leak-free and maintenance-free.
Potential Features
- Completely sealed
- High surge current
- Vibration resistant
- Leak-proof
- No maintenance required
Common Applications
- Backup power
- Trucks/cars
- Marine
Ease of use and affordability make AGM batteries more popular. At the same time, they have deep cycling limitations and do not last long.
What Is Lithium Battery?
Lithium batteries, especially Lithium Iron Phosphate (LiFePO4) batteries, are considered the advanced alternative to the traditional lead-acid/AGM batteries.
What makes lithium batteries stand out is their advanced chemistry and a Battery Management System (BMS). BMS protects batteries against various issues, such as short circuits, overcharging, and overheating.
A great example of lithium technology is the Renogy Pro 12V 100 Ah LiFePO4 battery that comes with a self-heating function.
Potential Features
- Longer lifespan
- Fast charging
- High energy density
- Deep discharge ability
- Lightweight structure
Common Applications
- Off-grid systems
- Camper vans
- Solar power systems
- Electric Vehicles (EVs)
- Marine uses
AGM Battery vs. Lithium Battery: A Quick Comparison
The table below briefly compares AGM vs. lithium batteries based on different factors.
| Feature | AGM Battery | Lithium Battery |
| Efficiency | 70-80% | 95-98% |
| Usable Capacity | Approx. 50% | 90-100% |
| Charging Speed | Slow | Fast |
| Safety | Marginal | High (BMS Protection) |
| Weight | Heavy | Lightweight |
| Cycle Life | 300-500 cycles | 4,000-10,000 cycles |
| Lifespan | 3-5 years | 10-15 years |
| Maintenance | Low | None |
| Upfront Cost | Low | High |
| Best For | Backup and starter | Solar and deep cycle |
AGM Battery vs. Lithium Battery: Key Differences
This section highlights and discusses differences by comparing an AGM battery vs. a lithium battery.
1. Lifespan
Your AGM battery can perform well for 3-5 years if used regularly. In contrast, a lithium battery lasts longer than the AGM one; it can deliver power for more than 10 years and even last for 15-20 years if used carefully.
Moreover, the lithium battery outperforms the AGM battery in terms of cycle life. An AGM battery lasts for 300-500 cycles on average, whereas a lithium battery is built to last for at least 4,000 cycles. In terms of life span and cycle life, buying a lithium battery is a long-term investment.
2. Depth of Discharge (Usable Capacity)
You can not discharge AGM batteries more than 50% to protect them from damage. On the other hand, lithium batteries allow you to use 90-100% of their capacity safely, making them a better choice. It simply means that a 100 Ah lithium battery can deliver double the power of a 100 Ah AGM battery.
3. Size and Weight
AGM batteries are bulkier than lithium ones. The average weight of AGM batteries ranges from 30 pounds (13.6kg) to 60 pounds (27 kg). Common AGM batteries for cars weigh 40-50 pounds and 60-100 pounds for solar or marine applications.
In contrast, the weight of a typical 12V 100 Ah lithium battery is between 22 pounds (10 kg) and 30 pounds (14 kg). Generally, lithium batteries are 50-70% lighter than AGM batteries of the same capacity.
4. Efficiency and Charging Speed
AGM batteries offer 70-80% round-trip efficiency, which means 15-20% of energy is lost during the charging process. Whereas lithium batteries come with 95-99% round-trip efficiency, meaning very little energy compared to AGM batteries is lost during charging.
The charge rate of AGM batteries is usually 10-30% (0.1C-0.3C) of their capacity. They charge faster than traditional lead-acid batteries, but slower than lithium ones. They quickly gain 80% charge, whereas the remaining 20% takes longer.
Lithium batteries charge much faster than their AGM alternatives. They can charge safely at 0.5C-1C. They gain 80-100% charge quickly with minimum delay near full capacity.
5. Cost (Upfront and Long-Term)
The upfront cost of AGM batteries is 2-4 times lower than that of lithium batteries. AGM batteries can last for 500-1,500 cycles, and you may need to replace them every 3-7 years. Frequent replacement means a higher long-term cost.
In contrast, lithium batteries offer a much longer lifespan. They can last for 4,000-10,000+ cycles and deliver consistent power for 8-15+ years. Despite the higher initial cost, they are cost-effective in the long term, as they don’t need frequent replacements.
6. Power Output
AGM batteries offer moderate power output with significant voltage drop under load. Limited usable capacity reduces the overall performance. These batteries can't run high-demand appliances properly, such as motors and inverters.
Lithium batteries are known for providing consistent and high power output with a stable voltage curve. They give more runtime with 80-100% usable capacity. You can easily power high loads with lithium batteries.
7. Maintenance and Ease of Use
AGM batteries are sealed and don’t need water topping. Still, you should charge them properly to prevent damage. The heavyweight structure makes them less user-friendly, especially for frequent handling.
Lithium batteries are maintenance-free. They come with a built-in BMS that offers protection against temperature, discharge, and overcharge. The plug-and-play feature and lightweight structure make these batteries very easy to use.
8. Temperature Performance
When it comes to performing in cold temperatures, AGM batteries outperform lithium batteries. You can use them in freezing conditions. Though their capacity drops in below-freezing environments, you can still use them. High temperatures shorten the lifespan of AGM batteries, but they can still handle it fairly well.
Lithium batteries perform well in moderate temperatures but are sensitive to cold weather. Charging them without heating can be unsafe. Additionally, these batteries can’t tolerate extreme heat. Reputable brands like Renogy offer advanced lithium batteries with built-in self-heating functionality.
Pros and Cons of AGM Batteries
Let's explore the advantages and limitations of AGM batteries.
Pros
- Simple charging system
- Suitable for starting the engine
- Affordable
- Performs well in cold temperatures
Cons
- Shorter lifespan
- Slow charging
- Heavier
- Limited usable capacity
Pros and Cons of Lithium Batteries
Below are the positives and drawbacks of lithium batteries.
Pros
- High efficiency
- Longer lifespan
- Lightweight
- More usable capacity
- Fast charging
Cons
- Don't perform well in cold climates
- Expensive
- Needs a compatible charging system
Which Battery Should You Choose for Different Applications?
Both batteries perform well in different situations, as listed below.
- Cars and Starter Batteries: AGM batteries offer better performance for providing short bursts of power to start engines at a lower cost.
- Solar Power Systems: Longer lifespans, deep cycling, and higher efficiencies make lithium batteries the best choice for solar power systems.
- Marine and Boating: AGM batteries are preferred for engine starting, whereas lithium batteries deliver power to run the electrical systems.
- RV and Camper Vans: Lithium batteries perform better for long trips and off-grid living than AGM batteries.
- Backup Power: AGM batteries are widely used for backup power due to their reliability and cost-effectiveness.
AGM vs. Lithium Batteries | Common Myths
Millions of people are concerned about the following myths.
Myth 1: Lithium batteries do not work in cold climates.
Fact: They work in cold weather, but may need temperature control to ensure proper charging.
Myth 2: AGM batteries are cheaper.
Fact: Only the upfront cost of AGM batteries is lower. Lithium batteries are more affordable in the long run, as they don’t need frequent replacements.
Myth 3: Lithium batteries are unsafe.
Fact: Modern Lithium Iron Phosphate (LiFePO4) batteries are extremely safe.
Summing Up
If you need a reliable battery option for starting your vehicle’s engine, look no further than an AGM battery. It is an affordable choice, but it can’t handle heavy appliances for extended hours.
On the other hand, if you are aiming for long-term savings, better performance, and higher efficiency, a lithium battery is what you need. It offers a longer lifespan, improved performance, and more runtime.
FAQs About AGM Battery vs Lithium
Can I replace an AGM battery with a lithium battery?
Yes, it is very common to replace an AGM battery with its lithium counterpart. In some upgrades, you may need to ensure that your setup supports different voltage profiles and the charger is lithium-compatible.
What makes AGM batteries heavy?
The higher weight of AGM batteries is due to heavy lead plates and absorbed glass mat separators (soaked with electrolyte).
Which battery performs well in a cold climate?
Lithium batteries struggle to perform well below 0°C, whereas AGM batteries offer much better performance in cold weather.
Why is a lithium battery costly?
A range of features add up to the total cost, such as higher efficiency, advanced lithium technology, long lifespan, and built-in BMS. Remember, only the upfront cost of lithium batteries is high (as stated earlier); they are affordable for long-term usage.
