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Battery Voltage Chart

Battery voltage charts are used to describe the relationship between a battery’s state of charge and the voltage at which they run.

Different types of batteries will require charts of their own but we’re going to cover both lead-acid and lithium-ion batteries. 

By the end of this article, you’ll know which battery will work best in your solar system.

Lead-Acid Battery Voltage Chart

When we speak about lead-acid batteries, we’re either talking about flooded lead-acid batteries or AGM batteries.

12 v battery voltage chart

The less expensive battery on the market is the former, commonly known as a wet cell battery. 

A lot of care will be required if you want to make sure that this battery lasts for months. 

This includes executing routine equalization charges and checking the water levels. 

While hydrogen gas is known to be produced by these batteries, ventilation will be necessary to get rid of the fumes.

Due to its low cost, this form of battery is frequently used in portable off-grid solar systems, but as wet cells start to have issues, users find themselves converting to lithium.

AGM lead acid batteries allow the electrolytes to be absorbed by the battery, which is positioned between two fiberglass mats. 

Less maintenance is needed because the battery is sealed.

These batteries are superior to wet cell batteries in practically every category. These are the superior lead acid batteries in terms of charge cycles and weight.

Flooded Lead-Acid Battery Voltage Chart

Based on factors including temperature, discharge rate, and battery type, lead acid battery voltage curves can vary significantly.

lead acid battery voltage chart

The table below shows a 6V battery voltage chart using a wet cell. The readings are obtained after testing a battery under standard, room temperature, conditions.

Voltage 

Capacity 

6.32V 

100%

6.26V

90%

6.20V 

80%

6.15V

70%

6.09V

60%

6.03V

50%

5.98V

40%

5.94V

30%

5.88V

20%

5.82V

10%

5.79V

0%

AGM Lead-Acid Battery Voltage Chart

When looking at an AGM battery charge chart, you’ll notice that it takes a higher voltage to reach maximum charge capacity compared to the wet cell. 

battery voltage chart 12v

A higher quality battery requires a higher voltage to max out

Voltage 

Capacity 

6.44V 

100%

6.39V

90%

6.33V 

80%

6.26V

70%

6.20V

60%

6.11V

50%

6.05V

40%

5.98V

30%

5.90V

20%

5.82V

10%

5.79V

0%


12V Lead-Acid Battery Voltage Chart

12V sealed lead acid batteries, or AGM, reach full charge at around 12.89 volts and reach complete discharge at about 12.23 volts.

12v battery voltage chart

The table below shows a voltage chart of a 12V lead acid battery

Voltage

Capacity

12.89V

100%

12.78V

90%

12.65V

80%

12.51V

70%

12.41V

60%

12.23V

50%

12.11V

40%

11.96V

30%

11.81V

20%

11.70V

10%

11.63V

0%


12V flooded lead acid batteries reach full charge at around 12.64 volts and reach complete discharge at about 12.07 volts.

2 volt battery voltage chart

Below is a table showing a flooded lead-acid 12V battery chart and it has a lower maximum: 

Voltage

Capacity

12.64V

100%

12.53V

90%

12.41V

80%

12.29V

70%

12.18V

60%

12.07V

50%

11.97V

40%

11.87V

30%

11.76V

20%

11.63V

10%

11.59V

0%


Lithium-Ion Battery Voltage Chart

Lithium iron phosphate batteries are the most common batteries used in solar systems. 

battery charging voltage chart

In fact, these batteries are commonly used in solar panel voltage charts as they provide excellent quality.

They may be stored without ventilation and are the safest batteries on the market. They also don't need to be fully charged in order for you to use them, and require little to no upkeep. 

In order to prevent the need for frequent replacement, the batteries are made to be rechargeable several times.

Battery management systems for lithium batteries are also available, and they keep an eye on the battery's condition. 

If the battery overheats, it will momentarily shut off the device until it has cooled. This provides the battery with an additional layer of security.

A more potent and durable battery bank can be made by stacking and expanding these cells.

Lithium iron phosphate batteries have gained much more traction, mostly due to the sharp price declines we've seen over the past ten years.

Let’s look at a cell voltage chart for a LiFePO4 battery 12v and see how it compares to lead-acid batteries.

Voltage

Capacity 

14.6V

100% (charging)

13.6V

100% (resting)

13.4V

99%

13.3V

90%

13.2V

70%

13.1V

40%

13.0V

30%

12.9V

20%

12.8V

17%

12.5V

14%

12.0V

9%

10.0V

0%

Larger batteries are necessary for bigger solar systems, so let’s look at the voltage chart for a 48V lithium-ion battery.

Voltage

Capacity 

57.6V

100% (charging)

54,4V

100% (resting)

53.6V

99%

53.2V

90%

52.8V

70%

52.4V

40%

52.0V

30%

51.6V

20%

51.2V

17%

50.0V

14%

48.0V

9%

40.9V

0%


Battery Charging Voltage Chart

Reading the terminal voltage or the electrolyte's specific gravity reveals the state of charge of the battery. 

The state of charge affects the density or specific gravity of the sulfuric acid electrolyte in a lead-acid battery. 

A hydrometer is used to read specific gravity, and the readings reveal the actual state of charge. With lead acid batteries, the hydrometer is not utilized.

Voltage meters are also used to show the charge level in a battery. 

12 v battery charge chart

Although fairly pricey, the digital ones give accurate voltage readings. 

The issue with using voltmeters only is the significant day-to-day voltage change. 

The charge and discharge states have a significant impact on a battery's voltage. The voltage of a battery rises when it is charged, falling when it is discharged.

Percentage of Charge 

12V Battery Voltage

Specifc Gravity using Hydrometer 

100%

12.70

1.265

95%

12.64

1.257

90%

12.58

1.249

85%

12.52

1.241

80%

12.46

1.233

75%

12.40

1.225

70%

12.36

1.218

65%

12.28

1.204

55%

12.24

1.197

50%

12.20

1.190

45%

12.16

1.183

40%

12.12

1.176

35%

12.08

1.169

30%

12.04

1.162

25%

12.00

1.155

20%

11.98

1.148

15%

11.96

1.141

10%

11.94

1.134

5%

11.92

1.127

0% (Discharged)

11.90

1.120


Battery Discharge Chart

The battery discharges whenever a load is connected to it because it draws current from it.  

battery charge chart

The process of battery discharge can be thought of as one through which a battery loses all of its charge. 

The battery discharges more quickly the more current the load draws. 

Different batteries are used for different reasons, meaning that we can use two different discharge intervals with the batteries.

Battery or Battery Pack Ah Rating 

7 Minunute 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

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