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 is from the Power Queen lab.

Example product:

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

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

Comparison Summary

batterytype

lead-acid batteryn

LiFePO4 Bbattery

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 of discharge

bad

bad

good

good

Temperature tolerance

bad

bad

good

good

Lifetime

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 a concern. In this comparison we look at the weight, dimensions, model specifications and energy density of VRLA and LFP batteries.

Battery backup

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 10.97lb for the LFP-50AH to 60.4lb 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 ratings 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 choosing a battery, it's important to consider both weight and energy density to ensure the battery is right 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. B 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 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 a significantly poorer voltage stability during rate discharge.

Each curve in the graph illustrates the effects of a 0.2C rate discharge on the voltage stability, with the lead-acid battery voltage dropping rapidly and the LFP battery exhibiting 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 losses and reduce the overall efficiency of the battery. Higher internal resistance also means that more power is required to drive the same amount of current through the battery, which can lead to 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 a high internal resistance. The plates inside the battery are made of lead, which has a relatively low conductivity compared to other metals such as copper. Also, the electrolyte used in lead-acid batteries is a dilute solution of sulfuric acid, which has a relatively high resistivity compared to other types of electrolyte. 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 a battery's performance. Even when a battery is not in use, it gradually loses its charge due to chemical reactions within the battery. Self-discharge rate may vary depending on battery type and age, as well as other factors such as temperature and storage conditions. Self-discharge can be a problem for devices that are not used frequently, as the battery can lose its charge before it can be used again. It can also reduce the overall capacity of the battery 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 self-discharge than lead-acid batteries. These properties contribute to the superior capacity and longer life of LiFePO4 batteries.

Comparison of the 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 of the specified range can result in irreparable damage to the internal components and reduced capacity, shorter lifespan, and even safety hazards such as leakage or explosion. In general, high temperatures can speed up chemical reactions within the battery, leading to faster degradation and reduced performance, while low temperatures can slow down 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 each type of battery and ensure that it is operating within the recommended temperature range. This can help extend battery life and maintain its performance and safety over time.

Now let's look at the comparison of these two battery types.

Type

VRLA-100Ah

VRLA-50Ah

LFP-100

LFP-50

Initial stress

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 larger temperature tolerance compared to lead-acid batteries.

Water resistance test

Water resistance means that the battery is designed to resist damage from 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 when 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 care 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 cycle capacity

High temperature cycling refers to exposing a battery to temperatures above the recommended operating range for an extended period of time. This can lead to accelerated battery degradation, resulting in reduced capacity and shorter lifespan. It can also increase the risk of safety hazards such as leaks, swelling, or even thermal runaway. Now we put the batteries in 55° (131°F) to see how their performance is.

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 represented 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 each cell.

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

LFP battery

Inside the LFP battery, there are structural protections such as protective plates and foam wadding with various functions, and the internal structure of the internal single cells has short-circuit protection.

Completion

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 life, faster charging, better performance, safety, and no 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 are planning to replace your trolling motor or RV battery, investing in a LiFePO4 battery could be a good choice.