# Lithium (LiFePO4) Battery Charge Time Calculator & Formula

Use our lithium battery charge time calculator to find out long how long it will take to charge a lithium battery with solar panels or with a battery charger.

I will share two Lithium-ion (LiFePO4) battery charge time calculators.

1. Lithium Battery Charge Time Calculator with solar panels
2. Lithium Battery Charge Time Calculator with battery charger

## Lithium (LiFePO4) Battery Charge Time Calculator with solar panels

Battery Capacity
Ah
Battery Volts
V
Battery Depth of Discharge
%
Solar Panel Size
Watts
Charge Controller Type

### Calculator assumptions

• Lithium battery charge efficiency – 95%
• Charge controller efficiency – PWM: 80%, MPPT: 98%
• Solar panel efficiency80%

### how to use this calculator? (example)

1. Enter the battery capacity in amp-hours (Ah). Let’s say you have a 100ah lithium battery (enter 100).
2. Enter the battery volts. Is this a 12, 24, or 48-volt battery? Let’s say you have a 12v battery (Enter 12).
3. Enter the battery depth of discharge (DoD): Battery Depth of discharge refers to the percentage of a battery that has been discharged relative to the overall capacity of the battery. For example, if your battery is discharged at 80%, enter 80.
4. Enter the solar panel size in watts. If you have multiple solar panels connected together, add up their rated wattage and enter the number (2 x 100W = 200W).
5. Select the charge controller type. Are you using a PWM or an MPPT charge controller? Choose accordingly.

### Example: How Long Does It Take To Charge A 12V Lithium Battery? Screenshot from calculator: How long to charge 100ah lithium battery from 80% DoD with 200 watt solar panels?

A 12v lithium battery will take anywhere between 5 – 20 hours to get fully charged.

## Lithium (LiFePO4) Battery Charge Time Calculator with battery charger

Battery Capacity
Battery Depth of Discharge
%
Charge Current

Note: If the battery capacity is mentioned in watt-hours (Wh) or kilowatt-hours (kWh), follow the below steps.

• For watt-hours (Wh): If the battery capacity is mentioned in watt-hours (Wh), divide the Wh numbers by the battery voltage (which will be mentioned in the specs sheet).
• For kilowatt-hours (kWh): If the battery capacity is mentioned in kilowatt-hours (kWh), Divide the kWh numbers by the battery voltage and then multiply it by 1000.

### How to use this calculator?

1- Enter the battery capacity and select the unit type from the list. For an instant, If you have a small battery in mAh capacity, select mAh and enter the capacity.

2- Enter the battery depth of discharge (DoD): Battery Depth of discharge refers to the percentage of a battery that has been discharged relative to the overall capacity of the battery. For example, if your battery is discharged at 80%, enter 80.

3- Enter the charge current and select the unit type from the list. It’ll be mentioned on your charger. For example, 2A, 4A, 10A, 20A etc.

4- Click “Calculate charge time” button for the result.

### Example Screenshot from the above calculator: how long does it take to charge 150ah lithium battery?

## How do you calculate lithium-ion battery charging time?

Here are the methods to calculate lithium (LiFePO4) battery charge time with solar and battery charger.

### 1: lithium battery charging time with solar panels

Formula: charge time = (battery capacity Wh × depth of discharge) ÷ (solar panel size × Charge controller efficiency × charge efficiency × 80%)

Battery depth of discharge (DoD): Battery Depth of discharge refers to the percentage of a battery that has been discharged relative to the overall capacity of the battery.

Lithium battery charge efficiency: 90 – 95% `(Source)`

Note: In real world, the battery charge efficiency rate will not be fixed and will depend on a number of factors. Like the battery charge rate (the faster the charge rate is the less efficient it is) and the battery depth state of charge (SOC).

Charge controller efficiency – PWM: 80%, MPPT: 98%

Battery capacity in watt-hours (Wh) = Battery Ah × Battery volts

#### Example

Let’s suppose

• Battery capacity: 12v 100Ah lithium battery (100 × 12 = 1200Wh)
• Solar panel size (W): 200 watt
• Charge controller type: MPPT
• DoD: 80%
``Charge time = (1200 × 80%) ÷ (200 × 98%  × 95% × 80%)``
``Charge time: (960) ÷ (148.9) = 6.4 hours``

### 2: lithium battery charge time using battery charger

Formula: charge time = (battery capacity × depth of discharge) ÷ (charge current × charge efficiency)

Note: Enter the battery capacity in Ah or mAh if the charger current output is mentioned in amps (A) or milliamps (mA). However, if the output value of the charger is mentioned in watts (W) or watt-hours (Wh), enter the battery capacity in watt-hours (Wh).

#### Example

Let’s suppose

• Battery Capacity: 100Ah
• Battery DoD: 100%
• Charge current: 10A
``Charge time: (100 × 100%) ÷ (10 × 95%)``
``Charge time: (100) ÷ (9.5) = 10.5 hours``

100Ah lithium battery will take about 10.5 hours to get fully charged from 100% depth of discharge (0% SoC) using a 10A charger.

## How long to charge a lithium (LiFePO4) battery?

Calculating the battery’s exact charge time is not an easy task. However, you can use our above lithium battery charge time calculators or formulas to get an estimated battery charge time.

There are many real-life factors that will affect the battery charge time, and it is nearly impossible for me to cover them all in calculators or formulas. Here’s why…

### Shortcomings of all the above methods

1 – Battery life cycles count: Batteries lose their charge-holding capacity as they age or after a few hundred cycles. After 1000 cycles, a 100Ah lithium battery may only be able to store 80Ah.

2 – Battery charger efficiency: The battery charging efficiency will depend on the battery’s state of charge. A charge will deliver 100% of its current to the battery when the battery is between 0-80% charged. But when it’ll reach 80% state of charge (SoC) the charger will drastically decrease the charge current. You’ll see if you have an iPhone, which takes longer to charge when the battery charge past 80%.

## Other useful calculators

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