Maximizing the power with LIFEPO4 batteries: a comparison to lead batteries
, From PQ DE, 16 min reading time
Choosing the right battery is crucial for many applications, such as solar power systems, electric vehicles, and marine applications. Two of the most popular battery types are LiFePO4 and lead-acid batteries. In this article, we explore the differences between LiFePO4 and lead-acid batteries and argue why LiFePO4 is the better option.
Announcement: All data is taken from the Power Queen Laboratory.
Example product:
LFP-50: Power Queen 12.8V 50Ah LiFePO4 Battery
LFP-100: Power Queen 12.8V 100Ah LiFePO4 battery
Summary of the comparison:
| batterytype | Lead-acid batteryn | LiFePO4 Bbatteries | ||
| VRLA-50AH | VRLA-100AH | 12V50Ah | 12V100Ah | |
| Energy density | low | low | 3 just higher as Lead-acid battery | 3 just higher as Lead-acid battery |
| Internal resistance and Self-discharge | high | high | low | low |
| rate discharge | bad | bad | good | good |
| Temperature tolerance | bad | bad | good | good |
| life | 300 | 300 | 4000 | 4000 |
Energy density – comparison of weight, size and capacity
When selecting a battery, battery weight and size are important factors to consider, especially in applications where mobility is critical. In this comparison, we examine the weight, dimensions, model specifications, and energy density of VRLA and LFP batteries.
| Battery type | Weight(kg） | Dimension(cm3） | Model | Energy density (Ah/kg) |
| VRLA-50 | 15.15 | 23*13.8*21.1 | 12V55Ah | 3.63 |
| VRLA-100 | 27.40 | 33*17.1*21.4 | 12V100Ah | 3.65 |
| VRLA2-100 | 28.11 | 33*17.1*21.4 | 12V100Ah | 3.56 |
| LFP-50 | 4.98 | 17*19*17 | 12V50Ah | 10.04 |
| LFP-100 | 9.85 | 32*17*21 | 12V100Ah | 10.15 |
In this comparison, we looked at five different batteries: VRLA-50AH, VRLA-100AH, VRLA2-100AH, LFP-50AH, and LFP-100AH. These batteries ranged in weight from 10.97 lb for the LFP-50AH to 60.4 lb for the VRLA-100AH. The battery dimensions also varied, with sizes ranging from 6.7 x 7.5 x 6.7 inches for the LFP-50AH to 13 x 6.7 x 8.42 inches for the VRLA-100AH and VRLA2-100AH.
Model specifications also differed between batteries, with voltage and capacity ratings ranging from 12V 50Ah for the LFP-50 AH to 12V 100Ah for the VRLA-100 AH and the LFP-100 AH. Finally, we compared the energy density of each battery in Ah/kg, with the LFP batteries exhibiting significantly higher energy densities than the VRLA batteries. Overall, when selecting a battery, it's important to consider both weight and energy density to ensure the battery is suitable for your specific application.
Rate discharge capacity comparison
Rate discharge capacity refers to the maximum amount of current a battery can discharge over a given period of time, usually expressed in amperes (A) or as a multiple of the battery capacity, e.g., C/10 or C/20. It represents the battery's ability to deliver energy at a given rate, with higher rates corresponding to faster discharge and lower rates corresponding to slower discharge. Rate discharge capacity is an important performance characteristic of a battery, especially for applications requiring high output power, such as electric vehicles or power tools.
Compared to LFP batteries, LA batteries have significantly worse voltage stability during rate discharge.
Each curve in the graph illustrates the effect of discharging at a rate of 0.2 C on voltage stability, with the lead-acid battery's voltage dropping rapidly and the LFP battery showing much greater stability.
Comparison of internal resistance and self-discharge
Internal resistance is an important property of a battery that can affect its performance. When a battery is used, the flow of electrical current generates heat within the battery due to the resistance it provides. This heat can lead to energy loss and reduce the battery's overall efficiency. Higher internal resistance also means more power is required to drive the same amount of current through the battery, which can lead to a voltage drop and a reduction in battery capacity.
|
| VRLA-50 | VRLA-100 | VRLA2-100 | LFP-50 | LFP-100 |
| Internal resistance (mΩ) | 7.95 | 5.23 | 4,553 | 1 | 1 |
We can see that lead-acid batteries have a very high internal resistance. Lead-acid batteries have a high internal resistance due to their design and chemistry. The plates inside the battery are made of lead, which has a relatively low conductivity compared to other metals like copper. Additionally, the electrolyte used in lead-acid batteries is a dilute sulfuric acid solution, which has a relatively high resistance compared to other electrolyte types. These factors contribute to the overall high internal resistance of lead-acid batteries, which can affect their performance and efficiency.
Self-discharge is another important factor affecting battery performance. Even when a battery isn't in use, it gradually loses its charge due to chemical reactions within the battery. The self-discharge rate can vary depending on the battery type and age, as well as other factors such as temperature and storage conditions. Self-discharge can be a problem for devices that aren't used frequently, as the battery may lose its charge before it can be used again. It can also decrease the battery's overall capacity over time, which can affect its performance and lifespan.
| type | day 1 | day 6 | day 11 | day 16 | day 21 | day 26 | day 31 | |
|
VRLA | 50 | 13.20 | 13.18 | 13.16 | 13.15 | 13.15 | 13,14 | 13.15 |
| 100 | 13.24 | 13.20 | 13.17 | 13.15 | 13.11 | 13.07 | 13.05 | |
|
PQ | 50 | 13.27 | 13.27 | 13.27 | 13.26 | 13.26 | 13.25 | 13.25 |
| 100 | 13.20 | 13.20 | 13.20 | 13.19 | 13.20 | 13.19 | 13.19 | |
According to the data, LiFePO4 batteries exhibit significantly lower internal resistance and lower self-discharge than lead-acid batteries. These characteristics contribute to the superior capacity and longer service life of LiFePO4 batteries.
Comparison of temperature tolerance
Temperature tolerance refers to the temperature range within which a battery can operate safely and effectively. Batteries are temperature-sensitive, and extreme heat or cold can significantly affect their performance and lifespan.
Exposing a battery to temperatures outside the specified range can cause irreparable damage to internal components, resulting in reduced capacity, shorter lifespan, and even safety risks such as leakage or explosion. Generally, high temperatures can accelerate chemical reactions within the battery, leading to faster degradation and reduced performance, while low temperatures can slow chemical reactions, making the battery less efficient and reducing its capacity.
Therefore, when selecting and using batteries, it is important to consider the temperature tolerance of the specific battery type and ensure that it is operated within the recommended temperature range. This can help extend the battery's lifespan and maintain its performance and safety over time.
Let’s now look at the comparison of these two battery types:
| type | VRLA-100Ah | VRLA-50Ah | LFP-100 | LFP-50 |
| Initial voltage | 13.05 | 13,15 | 13,19 | 13,19 |
| 80℃10 minutes | 13,03 | 13,13 | 13,19 | 13,19 |
| 25℃10 minutes | 13,03 | 13,14 | 13,19 | 13,20 |
| 80℃10 minutes | 13,01 | 13,11 | 13,19 | 13,20 |
| 25℃10 minutes | 13,00 | 13,11 | 13,20 | 13,20 |
| 80℃10 minutes | 12,58 | 13,09 | 13,20 | 13,20 |
| 25℃10 minutes | 12,57 | 13,10 | 13,20 | 13,20 |
The LiFePO4 battery has a greater temperature tolerance than lead-acid batteries.
Water resistance test
Waterproofing means that the battery is designed to resist damage from contact with water or other liquids.A waterproof battery is less susceptible to corrosion, short circuits, or other problems that could potentially damage it when exposed to moisture. However, it's important to note that waterproof batteries aren't completely immune to water damage and should still be handled with care in wet environments.
Rinse the battery with water for 10 minutes on each side and then measure the voltage before and after.
Lead-acid batteries have poor voltage stability before and after.
High-temperature cycle capacity
High-temperature cycling refers to exposing a battery to temperatures above its recommended operating range for an extended period of time. This can cause accelerated battery deterioration, resulting in reduced capacity and a shorter lifespan. It can also increase the risk of safety hazards such as leaks, swelling, or even thermal runaway. Now we'll place the batteries at 55° (131°F) to see how they perform.
Conclusion: The cycle stability of LA batteries is far worse than that of LFP batteries.
Capacity is represented by the blue curve and health is shown by the red curve.
Our battery estimation model suggests that a battery with a state of health (SOH) of 80% can last up to 300 cycles under normal use, while an LFP battery can last up to 4000 cycles.
We consider a battery with less than 80% SOH to be unacceptable according to our standards.
Experiment with disassembly to observe the internal structure
Lead-acid battery
There is almost no protection inside the LA battery, the air valve is just a rubber sleeve that can be easily removed, and there is no protection between the individual cells.
Removing the blue rubber sleeve directly exposes the inner pole piece and electrolyte. There is no internal protection.
LFP battery
Inside the LFP battery, there are structural protection devices such as protective plates and foam cotton with various functions, and the internal structure of the internal single cells has short circuit protection.
Conclusion
In summary, LiFePO4 batteries are an excellent option for powering marine applications such as trolling motors, electric vehicles such as RVs, and solar systems. They offer several advantages over lead-acid batteries, including light weight, longer lifespan, faster charging, better performance, safety, and maintenance-free operation. While they may be more expensive initially, their superior performance and longer lifespan make them a more cost-effective option in the long run. If you're planning to replace your trolling motor or RV battery, investing in a LiFePO4 battery could be a great choice.
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