How Long to Charge 12v Battery with 100 Watt Solar Panel?


In general, a 100W rated solar panel will take approximately 12.5 hours to fully recharge a 50% discharged 100Ah lead-acid deep-cycle battery by using an MPPT solar charge controller. At the same time, 200 watts of solar panels is recommended to recharge the same 100Ah battery in one day, if the battery is used for home energy storage.

How Much Power Can a 100 Watt Solar Panel Produce?

The table below shows the electrical specs. for a Centsys 100 watt panel.

Type of Module


Max Power




Open Circuit Voltage


Short Circuit Voltage


Max Power Voltage


Max Power Current


The main values that interest us are the open circuit volts (Voc) 22V, Maximum Power Point voltage (Vmpp) 18 V and Maximum Power Point current (Impp) 5.56A.

The typical manufacturer’s spec sheet uses the STC (Standard Test Conditions), which are ideal test conditions.

One important thing you need to know to is that these are ideal values under perfect laboratory test conditions.

However, it’s not easy to find these conditions in our daily life. In fact, expect to get only 75% of the stated power out of a standard quality 100 watt solar panel.

At the same time, you should know that any calculations on 75% of the stated maximum current, which for the above panel is a little over 4 amps.

Table – 100 solar panel annual energy output by irradiance per location


New York, NY

Birmingham, UK

Lisbon, PT

Brisbane, AU

Nairobi, KN

Irradiance (peak-sun-hours/day)






100W solar panel output per year (kWh)






100W solar panel output per day (kWh)

408.6 watts

216.5 watts

516.3 watts

527.5 watts

395.5 watts

How Many Solar Panels Does it Take to Charge a 100ah Battery?

Just imaging that a 100Ah solar panel current output of 4 amps minimum, then a 100Ah battery depleted 50% will need 12.5 hours to fully recharge.

On the condition that the solar battery was to be used as solar energy storage for use at night-time, then 200 watts of solar panels is recommended to ensure that the battery is recharged fully each day. So, now you have known the answer to this question. If you still don't know, please visit our official website, and our engineer will answer your questions.