Here are lead acid battery voltage charts showing the state of charge based on voltage for 6V, 12V, 24V, and 48V batteries.
Like all batteries, lead-acid batteries have different voltages at various stages of charge. For example, a 12V lead acid battery has a 12.73V voltage at 100% charge and an 11.36V voltage at 0% charge.
The voltage curves of lead acid batteries vary greatly depending on factors like temperature, discharge rate, and battery type (e.g. sealed batteries, flooded batteries). The general, averaged ones listed below should never take precedence over the voltage-to-battery capacity chart in your battery manual.
A lead-acid battery‘s remaining charge (or “juice”) can be calculated using the measured voltage.
6V Lead Acid Battery Voltage Charts
| 6V Lead Acid Battery Charge Voltage: | Battery Capacity (Percentage): |
| 6.37V | 100% |
| 6.31V | 90% |
| 6.25V | 80% |
| 6.19V | 70% |
| 6.12V | 60% |
| 6.05V | 50% |
| 5.98V | 40% |
| 5.91V | 30% |
| 5.83V | 20% |
| 5.75V | 10% |
| 5.71V | 0% |
Here we see that a 6V lead acid battery has an actual voltage of 6V at a charge between 40% and 50% (43%, to be exact). The voltage ranges from 6.37V at 100% charge to 5.71V at 0% charge.
Additionally, it’s crucial to remember that lead batteries have a depth of discharge (DoD) that is almost 50%. That means that only about 50% of the capacity of a lead-acid battery can actually be used.
Let’s move on to the most common 12-volt lead battery voltage chart:
12V Lead Acid Battery Voltage Chart (2nd Chart)
| 12V Lead Acid Battery Charge Voltage: | Battery Capacity (Percentage): |
| 12.73V | 100% |
| 12.62V | 90% |
| 12.50V | 80% |
| 12.37V | 70% |
| 12.24V | 60% |
| 12.10V | 50% |
| 11.96V | 40% |
| 11.81V | 30% |
| 11.66V | 20% |
| 11.51V | 10% |
| 11.36V | 0% |
Similarly to the 6V lead battery, we see that the 12V lead acid battery reaches the actually 12V voltage at the 40% to 50% range (43% is the exact capacity percentage).
At 100% charge, a 12V lead acid battery will have a 12.73V voltage. At 0% charge, a 12V lead acid battery will have an 11.36V voltage. Between a charge of 100% and 0%, there is a full 1.37V difference.
Onward to 24 lead acid battery chart:
24V Lead Acid Battery Voltage Chart (3rd Chart)
| 24V Lead Acid Battery Charge Voltage: | Battery Capacity (Percentage): |
| 25.46V | 100% |
| 25.24V | 90% |
| 25.00V | 80% |
| 24.74V | 70% |
| 24.48V | 60% |
| 24.20V | 50% |
| 23.92V | 40% |
| 23.62V | 30% |
| 23.32V | 20% |
| 23.02V | 10% |
| 22.72V | 0% |
The lead-acid discharge curve is the same for 24V lead-acid batteries, which have a 24V nominal voltage and a 43% capacity.
The 24V lead-acid battery voltage ranges from 25.46V at 100% charge to 22.72V at 0% charge; this is a 3.74V difference between a full and empty 24V battery.
Let’s have a look at the 48V lead-acid battery state of charge and voltage decreases as well:
48V Lead Acid Battery Voltage Chart (4th Chart)
| 48V Lead Acid Battery Charge Voltage: | Battery Capacity (Percentage): |
| 50.92V | 100% |
| 50.48V | 90% |
| 50.00V | 80% |
| 49.48V | 70% |
| 48.95V | 60% |
| 48.40V | 50% |
| 47.84V | 40% |
| 47.24V | 30% |
| 46.64V | 20% |
| 46.04V | 10% |
| 45.44V | 0% |
The discharge curve and relative states of charge (SOC) for even this higher voltage 48V lead-acid battery are the same.
The highest voltage 48V lead battery can achieve is 50.92V at 100% charge. The lowest voltage for a 48V lead battery is 45.44V at 0% charge; this is more than a 5V difference between a full and empty lead-acid battery.
We have some comparisons of lead acid batteries:
- Differences Between the Alkaline Battery and Lead Acid Battery
- Lead Acid Battery Vs Lithium-ion
- Gel Battery Vs Lead Acid Battery: Which is Better?
- Are AGM Batteries Better Than Lead-acid?
- Can You Mix Lead-acid and Lithium Batteries?
Ways to Check Lead Acid Battery Capacity
A lead acid battery’s capacity can be checked using a few different methods.
Measure Open Circuit Voltage With a Multimeter
To properly estimate battery capacity based on open circuit voltage, first disconnect everything from your battery and let it rest at room temperature for several hours. (At least 4 hours are advised, according to Battery University.)
Then, all you have to do is use a multimeter to measure the voltage at the battery terminals, and then compare the result to the state of charge chart in your battery manual. Use the pertinent chart from above if your battery manual is missing one.
Check Specific Gravity With a Hydrometer Or Refractometer
For measuring your lead acid battery’s so-called specific gravity, you can use a hydrometer or refractometer. Another method for determining the state of charge is to calculate the specific gravity.
This technique only works with flooded batteries because it necessitates opening the battery to access the electrolyte solution inside.
Use a Solar Charge Controller
Your charge controller most likely measures battery voltage for you if you’re using a lead acid battery in a solar power system.
You might believe that all you need to do to determine your battery’s capacity is to use this reading. Unfortunately, estimating capacity while a battery is connected to chargers and loads is very inaccurate when done using battery voltage.
Battery voltage varies greatly depending on factors like temperature and rate of discharge. Additionally, some charge controllers may provide an inaccurate reading of the battery voltage. Others have significant error margins, while some charge controllers only show one decimal place. For instance, one inexpensive PWM charge controller I tested claimed a battery voltage margin of error of +/- 0.2 volts.
Here is more information about lead acid batteries:
- Can Lead-acid Batteries Be Recycled?
- Can Lead-acid Batteries Explode?
- How Do Lead-acid Batteries Work?
- How Do You Charge a Lead-acid Battery?
- How Long Do Lead-acid Batteries Last?
- How Long to Charge the Lead Acid Battery?
- How to Desulfate a Lead Acid Battery?
Conclusion: Lead Acid Battery Voltage Charts
With these 4 voltage charts, you should now have full insight into the lead-acid battery state of charge at different voltages. Hopefully, you can now correctly calculate the battery charges and/or voltages using the lead-acid battery voltage charts.
Just keep in mind that, while it is perfectly acceptable to rely on generic lead acid battery voltage charts, using the chart provided by the battery’s (or the product’s) manufacturer will provide the best and most accurate information regarding the battery’s state of charge.
FAQs
What Voltage Should a Fully Charged Lead Acid Battery Be?
12.6V volts or above – Your battery is in good shape and is completely charged.
What Voltage is 50% of a 12V Battery?
The voltage on a fully charged battery will read 2.12 to 2.15 volts per cell, or 12.7 volts for a 12-volt battery. At 50% the reading will be 2.03 VPC (Volts Per Cell), and at 0% it will be at most 1.75 VPC.
What Voltage is Too Low for a Lead Acid Battery?
The truth is that any lead acid battery, be it a Gel Cell, AGM or flooded batteries such as DCBs should be cut off at 11.6 volts. If this is not done, the battery is more likely to sustain damage. If this damage extends too far into the battery’s charge, the battery will be destroyed.
