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How Fast Will 50-Watt Solar Panel Charge a Battery?


Most people underestimate a 50-watt solar panel which is quite unfair. It may not be ideal for a consistent supply of solar power throughout, but it is ideal for backup if integrated with the national power grid.

After all, it has the power to run most of the essential appliances in your home. It also comes in handy when traveling due to its portability.

However, how fast will a 50-watt solar panel charge a battery? No one wants to wait for days to get a full battery charge.

So, let’s find out to see if it is worth investing in, especially as a power backup. Read on!

How Long Does It Take a 50-Watt Solar Panel to Charge a 12V Battery?

First, this solar panel and the battery are an excellent combination. After all, the former can generate power to recharge the latter.

Now that the solar panel can recharge the battery, what remains a mystery is how long it will take. Here is an equation to help you figure it out!

It is about calculating a battery watt-hour which refers to the time the battery needs to recharge fully. Its formula is as simple as follows;

Amps x Volts = Battery Watt Hour

So, if you have a 50-Watt Solar Panels and a battery with a capacity of 30 Ah and a voltage of 12V, this equation will do the trick;

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12 x 30 = 360 watts

The above is the multiplication of the voltage and the battery capacity. The following equation is as follows;

Battery watt-hour / solar panel watt-hour = time necessary to charge the battery

360 / 50 = 7.2

It is the division of the answer in the previous equation by the solar panel wattage. The answer is the number of hours necessary to charge a 12V battery is approximately 7 hours.

However, it is worth noting that it is not always when your 12V battery will charge from 0. So, if it is halfway, you will use half its capacity to calculate the period.

The equations should be as follows;

12 x 15 = 180 watts

180 / 50 = 3.6

Therefore, it will take almost 4 hours to charge the same battery if it was halfway charged before you started recharging it. Expect the time to differ from one battery to another due to such fluctuations.

Besides saving you a lot of time, not waiting for the battery to discharge fully to recharge ensures that its lifespan is extended. Whereas most people assume it is only necessary for lead acid batteries, the same applies to their lithium-ion counterparts.

Which Appliances Can the 30 Ah Battery and the 50 Watts Solar Panel Power?

How rewarding is this wait if it takes about 7 hours to charge a 30 Ah and 12V battery using a 50-Watt solar panel? Let’s gauge that by looking at what such a combination can power.

The appliances that the pair can power include the following;

  • DC televisions
  • Electric blankets
  • Fans
  • Laptops

Despite not being strong enough to charge them for long, the solar panel can also charge heavy appliances such as mini-fridges and air pumps for several hours.

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Tips to Ensure that a 50-Watt Solar Panel Charges Your Battery Fast

The following tips ensure that your 50-watt solar panel charges your battery fast.

Choosing a Higher Battery Capacity

We have established that depleting your battery completely translates to more time as far as recharging is concerned. However, such a scenario is unavoidable if the power you need and the battery capacity are almost the same.

Under such circumstances, the solution would be to upgrade the battery capacity to a higher one. Since the battery never depletes, recharging fully takes a relatively short period.

Finding a High Rated Solar Panel

Whereas battery capacity is vital, one shouldn’t overlook the impact of solar panel efficiency. That’s why you should be keen on the efficiency rating of your solar panel.

The higher the rating, the better the choice. It ensures that the panel gets as much energy as possible from the sun whenever it appears.

The more solar power the panel produces, the faster the battery will charge. Besides, sunlight is crucial; the more exposure, the better the result.

Recharging Your Battery at 50%

Charging a depleted battery takes longer to recharge than one with some charge. That’s why it is advisable not to deplete your battery before recharging it.

Preferably, recharge it when it hits the 50% charge mark. Remember that this practice also boosts the longevity of your battery.

Why Is My 50-Watt Solar Panel Taking Longer to Charge the Battery?

Let’s refer to the example above. You have a 50-watt solar panel and a battery with a capacity of 30 Ah and a voltage of 12V. However, it takes more than 7 hours to charge.

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There are some factors contributing to this variance. The most common one is inadequate exposure to direct sunlight.

It could be a cloudy day or moments when the sun isn’t at its peak. Such conditions make working with your solar panel ratings and the charge time calculations wrong.

After all, they are only applicable when the solar panels are working under ideal conditions. If what you are dealing with isn’t ideal, there are high chances of the solar panel taking longer to charge your battery.

There is also the imperfection of the solar panels. It leads to the panels losing energy as it transmits to your battery.

There is nothing you can do about the energy loss since it isn’t a defect but the norm. However, some are worse than others hence the need to pay attention to a solar panel efficiency rating.

None of these ratings are perfect, but one between 20 and 25% is good. That’s why you should also consider the solar panel’s efficiency when calculating the time.

Here’s an example of a battery with a capacity of 20 amps and a voltage of 12V. The solar panel wattage remains to be 50 watts.

Amps x Volts = Battery Watt Hour

12 x 20 = 240 watts

Battery watt-hour / solar panel watt-hour = time necessary to charge the battery

240 / 50 = 4.8

However, we will introduce the 80% efficiency rate. It translates to dividing the time by 0.8

4.8 / 0.8 = 6

The bottom line is that the battery can charge in 4.8 hours if the conditions are ideal. However, it changes to 6 hours under different circumstances.

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