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AGM Battery Voltage Chart

Short on Time? Here’s The Article Summary

The article discusses AGM (Absorbent Glass Mat) batteries and their advantages in solar systems, comparing them to flooded lead-acid batteries. AGM batteries offer easier maintenance, higher durability, and better performance. The article includes charts illustrating voltage levels for different states of charge in 12V, 24V, and 48V AGM batteries.

It explains how to interpret these charts to determine the remaining capacity of the battery. The article also discusses discharge rates and how to choose the right AGM battery size for different solar system setups, such as RVs, homes, or farms. Overall, it emphasizes the benefits of AGM batteries for solar energy storage due to their efficiency and reliability.

Introduction

An AGM battery voltage chart describes the relationship between voltage, current, and the state of charge using recorded values. 

Further understanding these relationships will help make sense of your solar system’s components.

Let’s go over why so many people are opting for AGM batteries to use in their solar systems.

AGM Battery Charge Voltage Chart

AGM batteries fall under the category of lead acid, along with wet or flooded cell batteries. Yes, they’re both lead-acid, but there are distinct differences between the two. 

agm battery charge voltage chart

Flooded or wet-cell batteries are the most affordable option on the market. Lots of maintenance is necessary to ensure this battery lasts its lifetime. 

This includes regular equalization charges and checking the water levels. 

These batteries are known to emit hydrogen gas, ventilation will be required to remove the fumes.

Many people use this type of battery in their portable off-grid solar system because it is so inexpensive, but they eventually switch to lithium after wet cell becomes problematic. 

So if you’re planning to use a solar panel voltage chart, you’ll notice that an AGM battery outperforms.

AGM lead acid batteries are fitted between two fiber glass mats, allowing the electrolytes to be absorbed.

Since the battery is sealed, it requires less maintenance. 

In almost every category, these batteries outperform wet cell batteries. These are the best lead acid batteries in terms of charge cycles and overall weight.

Before we get into what an AGM battery charge voltage chart, let’s look at why so many people opt for these batteries. 

Advantages of AGM Batteries 

The unique design of AGM batteries allows them to deliver faster start-ups and an increased cold cranking power compared to your conventional lead acid batteries.

agm battery charging voltage chart

Their absorbent glass mat cell offers rugged durability and improved vibration resistance, as well as being spill and leak-proof. 

This is all due to the electrolyte being held within the mat instead of moving around in liquid like the flooded cell.

AGM batteries also excel in their repeated charging and discharging capabilities, so when we have a battery discharge voltage chart, we use an AGM battery.

AGM batteries have the capacity to absorb the recycled energy from breaking quickly and handling the excess energy without overcharging. 

These batteries drain at a much lower rate than conventional lead acid batteries.

AGM batteries are designed to withstand deep and repeated discharges.

The acid cannot escape from the AGM batteries due to the glass wool, and because gas discharge is minimal, it can also be installed in living spaces. 

They require no maintenance and do not require water to be replenished. In other words, these batteries will work perfectly for your solar system.

They’re also appropriate for use in the applications like camping, motor boats, and for  uninterrupted power supplies.

AGM Battery Charging Voltage Chart

Different charging or discharging currents have an effect on battery voltage when charging or discharging.

agm voltage chart

This means that the higher the current, the higher the voltage when charging. The higher the current in a discharging condition, the lower the voltage.

The battery’s voltage can be affected by the different manufacturers and production materials used in the hardware.

The battery's voltage varies with temperature. This means the lower the temperature, the lower the voltage.

The battery voltage will be reduced after a period of use and all AGM batteries have the same voltage discharge curve. 

That is why, by measuring the voltage and consulting the voltage discharge chart, we can use the voltage state of charge charts to determine how much energy is left in the AGM battery.

12-Volt AGM Battery Voltage Chart

When looking at the 12V AGM battery chart, the state of charge voltage of a 12V AGM battery ranges from 13.00V at 100% capacity to 10.50V at 0% capacity. 

12 volt agm battery voltage chart

If you measure the 12.30V voltage on your 12V AGM battery, for example, you can determine that this 12V AGM battery still has 70% capacity.

Voltage

Capacity 

13.00V

100% (charging)

12.85V

100% (resting)

12.80V

99%

12.75V

90%

12.50V

80%

12.30V

70%

12.15V

60%

12.05V

50%

11.95V

40%

11.81V

30%

11.66V

20%

11.51V

10%

10.50V

0%

 

24V AGM Battery Voltage Chart

In the AGM 24V lead-acid battery voltage chart below, the voltage ranges from 26.00V at 100% charge to 21.00V at 0% charge with this higher voltage 24V deep cycle battery.

agm battery state of charge chart

The absolute voltage difference between a full and an empty battery is 5.00V.

If you use a voltage meter and measure the difference between the cathode and anode of an AGM battery to be 23.50V, you can read from this chart that this 24V battery still has 20% to 30% charge left.

Voltage

Capacity 

26.00V

100% (charging)

25.85V

100% (resting)

25.75V

99%

25.55V

90%

25.00V

80%

24.60V

70%

24.30V

60%

24.10V

50%

23.90V

40%

23.62V

30%

23.32V

20%

23.02V

10%

21.00V

0%

 

48V AGM Battery Voltage Chart

The voltage ranges from 52.00V at 100% charge to 42.00V at 0% charge with a high voltage 48V deep cycle battery.

agm battery discharge chart

The absolute voltage difference between a full and an empty battery is 10.00V.

If you use a voltage meter and measure the difference between the cathode and anode of an AGM battery to be 47.00V, you can read from this chart that this 48V battery still has 20% to 30% charge left.

 

Voltage

Capacity 

52.00V

100% (charging)

51.70V

100% (resting)

51.45V

99%

51.10V

90%

50.00V

80%

49.20V

70%

48.60V

60%

48.20V

50%

47.80V

40%

47.24V

30%

46.64V

20%

46.04V

10%

42.00V

0%

 

AGM Battery Discharge Voltage Chart

An AGM battery’s ability to discharge deeply without any damage to the plates is a definite advantage for those wanting to use it in a solar system.

Charts and curves are commonly used to depict discharge.

We need to look at the depth of discharge to understand it. This is the percentage of power that can be drawn from a battery.

If we have an AGM battery with a depth of discharge of 45%, the load can only use 45% of the battery's capacity.

In other words, your 300Ah battery can only produce 165Ah at a depth of discharge of 45%.

deep cycle battery agm battery charge voltage chart

When a load is connected to the battery, the battery drains because the load draws current from the battery.

Battery discharge can be defined as the process by which a battery completely loses its charge.

The battery drains faster as the load draws more current.

Since different batteries are used for different purposes, we can use two different discharge periods to measure them.

Using the battery pack rating in the graph below, you can discover the discharge current for your battery in the same way that you’d use a 48V battery discharge chart

Simply get the Ah rating on your battery and look at the corresponding column.

Battery or Battery Pack Ah Rating 

7 Minute Maximum Discharge Current 

30 Minute Maximum Discharge Current

5Ah

15 Amps

10 Amps

7Ah

21 Amps

14 Amps

8Ah

24 Amps

16 Amps

9Ah

27 Amps

18 Amps

10Ah

31 Amps

21 Amps

12Ah

36 Amps

24 Amps

14Ah

42 Amps

31 Amps

15Ah

44 Amps

32 Amps

18Ah

57 Amps

40 Amps

22Ah

66 Amps

46 Amps

35Ah

105 Amps

84 Amps

Which AGM Battery to Choose for Your Solar System?

Choosing a battery size that works best in your system depends on its size.

If you want to power an RV, then opting for a 12V deep cycle battery for solar is perfect.

agm battery charge chart

The 24V AGM batteries are perfect for home solar systems that are in relatively sunny areas. 

Lastly, the bigger 48V AGM battery will suit those with a big home or a small farm.

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Article by

Cody Oehm

Cody is the Head of Marketing at Shop Solar, and joined the company in spring of 2022. 

He has an entrepreneurial background and has been in the ecommerce industry since 2015. With 4 businesses under his belt and a drive to make a bigger impact, he decided to team up with Shop Solar on their mission to make solar simple and affordable. You can browse best seller's here.

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