Battery Voltage Chart
Short on Time? Here’s The Article Summary
The article discusses battery voltage charts for lead-acid and lithium-ion batteries, focusing on their state of charge and voltage levels. Lead-acid batteries, including flooded and AGM types, require maintenance like equalization charges and water level checks. AGM batteries are more durable and require less maintenance. The article also compares the voltage charts of 6V and 12V lead-acid batteries.
For lithium-ion batteries, specifically lithium iron phosphate (LiFePO4), the article highlights their safety, longevity, and minimal maintenance requirements. The voltage chart for a 12V LiFePO4 battery is compared to lead-acid batteries, showing different voltage levels at various charge states. Additionally, the article discusses battery charging voltage charts, emphasizing the use of hydrometers or voltmeters to determine a battery's state of charge. It also touches on battery discharge charts, explaining how the discharge rate varies based on the load connected to the battery. The article concludes by mentioning the importance of selecting the right battery for solar systems based on their voltage characteristics.
Introduction
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.
Table of Contents
Lead-Acid Battery Voltage Chart
When we speak about lead-acid batteries, we’re either talking about flooded lead-acid batteries or AGM batteries.
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.
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.
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.
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.
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.
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.
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.
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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