Choosing the right battery is crucial for many applications, e.g. b for 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 examine the differences between LiFePO4 and lead-acid batteries and argue why LiFePO4 is the better option.

Announcement: All data comes from the Power Queen laboratory.

Example product:

LFP-50: Power Queen 12.8V 50 Ah LiFePO4 battery

LFP-100: Power Queen 12.8V 100Ah LiFePO4 battery

 

Summary of comparison

Batterytype	Lead-acid batteryn		LiFePO4 Bbatteries
	VRLA-50AH	VRLA-100AH	12V50Ah	12V100Ah
Energy density	low	low	3 times higher than lead-acid battery	3 times higher than lead-acid battery
Internal resistance and self-discharge	high	high	low	low
Rate Discharge	bad	bad	good	good
Temperature tolerance	bad	bad	good	good
Lifespan	300	300	4000	4000

 

Energy density – comparison of weight, size and capacity

When selecting a battery, the weight and size of the battery are important factors to consider, especially in applications where portability is important. In this comparison, we look at 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. The weight of these batteries ranged from 10.97 lb for the LFP-50AH to 60.4 lb for the VRLA-100AH. The dimensions of the batteries 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 values ​​ranging from 12V 50Ah for the LFP-50 AH to 12V 100Ah for the VRLA-100 AH and LFP-100 AH. Finally, we compared the energy density of each battery in Ah/kg, with the LFP batteries having significantly higher energy densities than the VRLA batteries. Overall, when selecting a battery, it is 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 amps (A) or as a multiple of the battery capacity, e.g. b C/10 or C/20. It represents the battery's ability to deliver energy at a specific 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 where high output power is required, such as: b 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 effects of discharging at a rate of 0.2C on voltage stability, with the lead-acid battery voltage dropping rapidly and the LFP battery having 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 creates heat within the battery due to the resistance it provides. This heat can cause energy loss and reduce the overall efficiency of the battery. Higher internal resistance also means more power is required to drive the same amount of current through the battery, which can result in 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 really high internal resistance. Due to their design and chemistry, lead-acid batteries have high internal resistance. The plates inside the battery are made of lead, which has relatively low conductivity compared to other metals such as copper. Additionally, the electrolyte used in lead-acid batteries is a dilute sulfuric acid solution, which has a relatively high resistance compared to other types of electrolytes. 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 that affects the performance of a battery. Even when a battery is not being used, it will gradually lose its charge due to chemical reactions within the battery. The self-discharge rate can vary depending on the type and age of the battery, as well as other factors such as temperature and storage conditions. Self-discharge can be a problem in devices that are not used frequently because the battery can lose its charge before it can be used again. It can also reduce 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

 

LFP battery wins again.

According to the data, LiFePO4 batteries have significantly lower internal resistance and lower self-discharge than lead-acid batteries. These features contribute to the superior capacity and longer lifespan 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 and result in reduced capacity, shorter lifespan, and even safety hazards such as leakage or explosion. In general, 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 operates within the recommended temperature range. This can help extend battery life and maintain its performance and safety over time.

Now let's see the comparison of these two types of batteries.

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 compared to lead-acid batteries.

Waterproof test

Waterproof means that the battery is designed to resist damage caused by contact with water or other liquids. A waterproof battery is less likely to suffer from corrosion, short circuits, or other problems that could potentially damage it if exposed to moisture. However, it is important to note that waterproof batteries are not completely immune to water damage and should still be handled with caution in wet environments.

Rinse the battery with water for 10 minutes on each side, then measure the voltage before and after.

	VRLA battery	LFP battery
Before	13.05V	13.19V
After	13.01V	13.19V

 

Lead-acid batteries have poor voltage stability before and after.

High temperature cycling capacity

A high temperature cycle refers to exposing a battery to temperatures above the recommended operating range for an extended period of time. This can cause accelerated battery degradation, resulting in reduced capacity and shorter lifespan. It can also increase the risk of safety hazards such as leaks, springs, or even thermal runaway. Now let's put the batteries in 55° (131°F) to see what their performance is like.

 

Conclusion: The cycle stability of LA batteries is far worse than that of LFP batteries.

Capacity is shown 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 individual cells.

Removing the blue rubber sleeve directly exposes the inner pole piece and electrolyte. There is no protection inside.

 

LFP battery

Inside the LFP battery there are structural protection devices such as protective plates and foam padding 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 freedom from maintenance. Although 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 on replacing your trolling motor or RV battery, investing in a LiFePO4 battery could be a good choice.

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