We use batteries in our daily life, so recharging the battery is what makes most of us confused.
Charging your battery on a higher voltage or current can increase the battery's plates temperature which as result will decrease the battery life cycles
So in this guide, I'll explain about maximum & minimum charging current and voltage for a 12v battery
Before we calculate the charging current and voltage first of all let's discuss the difference between current or amps and voltage
Voltage is the amount of pressure that is needed to let the electrons flow & Current or amp is the number of electrons
What is the maximum charging voltage for a 12-volt battery?
The charging voltage of the battery will depend on a few factors, its state of charge or discharge & weather temperature.
And of course, every battery will also have a different voltage limit while recharging
There are mainly 3 stages of charging the battery, Bulk, absorption, & Float stage
Bulk Stage: when the depth of charge of the 12v battery is 80%, the bulk stage means your battery is 80% discharged. So in this stage, the battery will use the maximum voltage input voltage
So a 12v lead-acid or AGM battery will use 2.4-2.45v per cell (Read the values on your battery). So 12v battery contains 6 cells so it'll be 14.4-14.7 voltage
Absorption Stage: When the battery is 80% charged is known as the absorption stage. So, in this case, the battery will maintain a lower voltage and the amps will decrease as the battery state of charge will increase
Float stage: This is the stage in which your battery is fully charged or in the maintenance stage. So, in this case, the voltage will decrease, and also the amps will be 0 or 1
If the battery isn't completely charged you can use higher voltage without causing any damage to the battery because the charging response takes priority over any over-charge chemical responses until the battery is completely charged. This is why a battery charger can operate at 14-15 volts during the bulk-charge phase of the charge cycle
When your battery is below 80% charged it will safely accept the higher voltage (read the spec of your battery to figure out the maximum voltage) and maximum current (Which should not be 20% of the total capacity of your battery)
When the battery is 80% charged then the voltage will stay stable 12-12.7 volts (Check the spec of your battery for accurate value) but the current or amps will start to decrease as the battery charge will get closer to 100%
if you're using a charge controller it will automatically do the calculations or you can manually put these values in case to increase the lifespan of your battery.
| Battery Discharge Stage | Voltage Required |
|---|---|
| 80% | 14-15v |
| 50% | 13-14v |
| 20% | 12-13v |
| 10% | 11.5-12v |
Note: Check your manufactures instructions about the discharge rate of the battery and its voltage. Every battery type and brand will have different numbers. This chart shows the average range which can be possible
Video - 12v battery voltage explained
AGM battery voltage chart
| 12v Battery | O°C (32°F) | 1O°C (50°F) | 2O°C (58°F) | 25°C (77°F) | 3O°C (86°F) | 4O°C (104°F) |
|---|---|---|---|---|---|---|
| Charge Voltage | 15.30v | 15.06v | 14.84v | 14.70v | 14.55v | 14.34v |
| Float Voltage | 14.40v | 14.16v | 13.94v | 13.80v | 13.88v | 13.44v |
as you can see as the temperatures rise the battery voltage will decrease so you'll have to set the voltage of your battery according to its state of charge or discharge and temperature.
Chart- 12v lithium battery state of discharge & voltage
| SOC (State of charge) | Voltage |
|---|---|
| 100% | 13.6V |
| 90% | 13.4V |
| 80% | 13.25V |
| 70% | 13.2V |
| 40% | 13.1V |
| 30% | 13.0V |
| 20% | 12.9V |
| 10% | 12.1V |
Chart- 12v lead acid battery minimum voltage
| SOC (State of charge) | Voltage |
|---|---|
| 100% | 12.73V |
| 90% | 12.62V |
| 80% | 12.50V |
| 70% | 12.37V |
| 60% | 12.24V |
| 50% | 12.10V |
| 40% | 11.96V |
| 30% | 11.81V |
| 20% | 11.66V |
| 10% | 11.51V |
SOC (state of charge) and voltage are used to check whether the battery is fully charged or not. You can use a DC meter to check the values of voltage to figure out the state of charge of your battery
Video - Battery Charging voltage & current in different stages (Bulk, Absorption, Float)
How many amps do i need to charge a 12 volt battery
Amps are the total flow of electrons in the battery. So how many maximum and minimum amps per hour to charge your 12v battery to increase the battery life cycles
As a rule of thumb, the minimum amps required to charge a 12v battery is 10% of its full capacity but the ideal charging current should be between 20-25% of the battery's capacity
For example. if you have a 12v 100Ah battery then you'll need a minimum of 10 amps and a maximum of 20-25 amps to recharge your battery
When the battery is charged below then 80% you can use 20% of the battery's capacity (Ah) to recharge the battery but when the battery reached 80% State of charge gradually decrease the amps and voltage will stay the same between 12-12.7V (Depends on different manufacturers)
Yes, you can exceed this number but it will increase the battery internal temperature which will decrease the battery life.
Related FAQ's
The maximum charging current for a lead-acid battery is 50% and 30% for an AGM battery. But recharging your battery at this much high amps will decrease the battery life cycles
lithium batteries can handle current up to 50% of their full capacity e.g 50Ah for 100Ah battery but charging your battery at this high amps will decrease the lifespan of your battery so 20% is recommended
The ideal charging current for a 120Ah battery is 24 amps when the battery is fully discharged but when the SOC is above 80% the amps will gradually start to decrease
maximum charging current for 150Ah battery should not be above 30 amps
Recommended maximum charging current for 200Ah battery is 40 amps
Yes, you can use a 12v power supply to charge your 12v battery
the ideal current or amps to charge a car battery are 20% of its full capacity e.g 10 amps for a 50Ah battery
the ideal charging current for a 12v 7ah battery is 1.4 amps
maximum charging current for 100Ah battery should not be above its 20% of full capacity (20 amps)
