If you’ve been planning to install an off-grid solar energy solution, it is an obvious thing one can ask: How many watts of solar panels do I need to charge a 150 AH battery? Or how much time it takes to 600 watts of the solar panels to charge a 150 AH battery full?
In this article, we’ll explain the basic calculation of the solar panels’ capacity or wattage requirements to charge a battery bank.
First, let us calculate the battery watts. Inverter batteries come in 12 Volts capacity, let’s say you have a 150 AH battery bank then multiply the battery’s AH with its Volts to calculate the total battery wattages.
150 AH * 12 Volts = 1800 WattsBattery AH * Battery Volts = Battery Watts
Second, in how many hours you want the battery bank to charge full using just solar panels. Let’s assume to charge a 150 AH battery full in just 4 hours. So divide the watts of battery by charging hours.
1800 Watts / 4 Hours = 450 WattsBattery Watts / Charging Hours = Watts Required
So, we would require more than 450 watts of solar panels to charge a 150 AH battery around 4 hours under a clear and sunny sky.
But, but, but…
Consider the current losses. You’ll need around 30% more watts to cover all the AC-DC current conversion losses.
When we are talking about a clear and sunny sky, things are not bright always. Weather conditions like clouds, rains, and winter season also affect solar energy generation, we need to take such conditions in the account as well.
TIP: Use MPPT charge controller technology over PWM to consume most from solar panels. Power losses are negligible in MPPT, whereas, PWM lose around 20 to 30 % of its energy.
If you’re relying completely on solar power, then add more watts of the solar capacity. This way you can rely on solar power in the day time and use the battery bank power at night time.