What Size Solar Panel To Charge 100ah Battery

Share This Post

Average Solar Panel Output In Peak Sun Hour

Off Grid Solar A/C System | 100 Amp Solar Panel 100AH Battery Setup

As we know that solar panels are rated their power under a controlled laboratory environment. But in the real world, there will be some power losses

These power losses will occur due to various reasons, here are some examples

  • Manufacturers output tolerance
  • Dirt and grime on panels
  • Temperature derating

On average. A solar panel will produce about 80% of its rated wattage output in real-world conditions.

This percentage is based on my personal experience with 400 watt solar panels. I collected the 30 days of total output from the solar panels and divide it by that months peak sun hours.

Yes, therell be sometimes when youll get 100% output from the solar panel but its rarely gonna happen and will last for a few minutes

I have a detailed post about this topic and shared some tips to get the maximum output from your solar panels.

Related Post: Solar Panel Output Calculator Average Solar Panel Output?

Can A 200w Solar Panel Charge A 100ah Battery

Recharging at the 50% level will prolong the life of your battery, and it shortens the charge time considerably. Instead of waiting 5 to 6 hours, it will only take 2 to 3 hours before the battery is fully charged. This does bring up the question: if you recharge the battery at 50%, do you still need 240W or 300W solar panels?

Technically, you can use a 200 watt solar panel to charge a 100ah battery if it is 50% full. But it will take about 5 hours or so. If the battery is at 0%, it will take all day. Even if it is at 50% level, you have to hope that the weather stays perfect for a fast charge.

As we have mentioned earlier, it is better to have a bigger solar panel than a small one. Even if the weather is perfect, there will be some energy loss due to poor wiring, dust on the solar panel, improper connection, or the panel orientation is not optimal.

Adding another 100 watt panel to your solar array is easy, and the cost has really dropped. The convenience you get is well worth the price. Just like the battery, you should never push your solar panels to their maximum capacity. Always leave some extra power as reserve.

Can You Charge A 24 Volt Battery With A 12 Volt Solar Panel

The short answer is yes, you can. However, you need to use a charge controller to convert the solar panels output into a more suitable current rating, so you can charge the battery without risking damaging it.

Its important to mention that its not recommended to charge a deep cycle battery with a solar panel of different voltage rating, as this will result in a lot of power loss.

Related article: Can Solar Panel Discharge Battery?

You May Like: Camry Hybrid Battery Replacement Cost

The Difference Between Auto And Deep

Then, theres first, the 100Ah automatic battery, lets say its discharged regularly to 20 percent:

100Ah x 20% = 20Ah

A 10Ah deep cycle leisure battery can be charged regularly until 50 percent:

100Ah x 50% = 50Ah

At 50 percent discharge, the deep-cycle battery will require more than double the amount of solar power to recharge it completely.

Ill take that the discharge is between 20 and 50 percent for the various types in my calculations.

How To Size Solar Panels Power Using Peak

120W WATT Foldable Solar Panel Kit Monocrystalline &  100AH Battery ...

Ill use 400Wh/day as an example, to show how it works. The calculation shows the number of 100 watt rated solar panels I would need to recharge each of the batteries:

Car battery: x 12 volts = 20 x 12 = 240 watt-hours.

One 100 watt solar panel could charge this battery in well under a day, about 5 hours.

Deep-cycle battery: = 50 x 12 volts = 600 watts-hours.

I would need 2 solar panels rated at 100 watts to recharge this battery in less than a day 2 x 100 watts generates about 800 Wh/day.

Solar circuits always have losses, so I would add 30 to 50% to solar panel size you come up with. As well as the power lost due to inherent circuit losses, every passing cloud will reduce the energy produced.

This chart gives some idea of how the suns energy can vary between physical locations and how the number of peak-sun-hours affects solar panel sizing:


You May Like: Who Makes Die Hard Batteries

How Long Will A 100

Consider several factors when judging the time it takes for a solar panel to charge a battery. You want to consider the weather, panel wattage, battery capacity, depletion, controller efficiency, and more.

However, you can also focus simply on battery capacity, solar panel watts, and sunlight hours. Estimate the time it takes for a 100-watt panel to charge a 12-volt battery by using this simple formula to calculate your charging time: x voltage/panel wattage.

In most cases, when the battery capacity matches the amps produced by the solar panels, fully charging a drained battery takes five to eight hours.

To make your life easy, you can use this simple cheat sheet to know how much time you need for a 100-watt panel to charge common 12V battery capacities:

  • One 50Ah battery takes about 4.8 hours.
  • One 80Ah battery takes nearly 8 hours.
  • One 100Ah battery takes about 10 hours.
  • One 120Ah battery takes approximately 12 hours.
  • One 200Ah battery takes just over 19 hours.

Why Use Peak Sun Hours

Sunlight varies in intensity by location and time of day. The sun shines more intensely at 1pm in Arizona than it does at 8AM in Alaska.

So if we were just to measure the length of time sun shines on a solar panel, it wouldnt give us a very clear idea of how much energy that solar panel generated during that time. We need to know how intense that sunlight was.

Plus, we can use historical data to predict how many peak sun hours a location will get on an average day. These predictions help when picking what size solar panel or system to use.

Recommended Reading: Lowe’s Battery Weed Eater

Factors To Consider When Buying A Solar Panel For Home

There are some other factors you need to consider while installing panels for the first time.

  • You may have a rooftop with damp conditions, and you need to make sure you are installing a solar panel in a dry and suitable area where it receives plenty of sunlight.
  • Avoid any shades above the panels, or it wont be able to get enough sunlight.
  • You might need to install a lightning guard, to avoid breaking your solar panels in case of lightning or thunderstorms, so it is advised to have lightning earthing.
  • Make sure you have a proper insulation, and it is waterproof, so that neither fire or short circuit happens.
  • In case of an unfortunate fire breakout, you need to have a fire extinguisher in case, or call local fire service immediately.
  • What equipment you wish to run, because you cant run an AC out of low power generation of the solar panels. This is why you need to double check what equipment you wish to run using solar panels, and take expert guidance regarding size and power you need to generate.

Choose The Right Charge Controller Size

Setting up solar charging for my 100Ah Lifepo4 battery

Your charge controller should be compatible with the amperage and watts going through the system. If you have a 20A 240 watt system, your charge controller must be able to match that. If you are running a 240 watt solar panel, you need at least a 300W capable charge controller.

There are two types of charge controllers, PWM and MPPT. PWM is the standard and works fine for most solar panels and batteries. MPPT charge controllers are more accurate and can handle greater power. But they are also more expensive. For charging a 100ah battery however, a 30A PWM controller the should be fine. Our choice is the EEEKit Solar Charge Controller as it does the job without any fuss.

Recommended Reading: Battery Bank For Solar Power

The Difference In Charging Auto And Deep

Assuming that the 100Ah auto battery is discharged down to 20%, you will need 100Ah x 20% = 20Ah. We also assume that the 100Ah deep-cycle battery is discharged down to 50%, meaning you will need 100Ah x 50% = 50Ah.

In the proceeding calculations, we will assume that the 100Ah auto battery can discharge to a maximum of 20% while deep-cycle discharges to 50%.

One terminology you should also know is Depth of Discharge , which shows how much battery power has been used. It tells you how much battery energy you need to replace using solar panels.

However, how do you know the remaining battery capacity?

You can use a multi-meter tester to check the terminal volts and determine the amp-hour capacity in your lead-acid battery.

Ensure the battery is dormant for approximately 6 hours before checking the remaining capacity to avoid stimulating a chemical reaction.

How Does A Solar Panel Work

A solar panel converts light into electricity. A solar panels power, or wattage, depends on its physical dimensions and efficiency, with voltage a key characteristic for battery charging.

Solar panels are generally part of a system rather than connecting directly to batteries. Before reaching a battery, solar energy from the panels will flow into a regulator or solar charge controller .

In many solar panels, we can observe an open circuit voltage of about 22 volts, and the SCC is there to prevent overcharging and battery damage. For example, a solar panel in full sunlight connected to a 12v battery could potentially charge at levels well above 12 volts.

The solar regulator detects the existing voltage and adjusts panel output when it approaches 14.1 volts to prevent damage from this. It also maximizes the current delivered by the solar panel and thereby keeps the charging time short as possible.

Voltage does not vary with light intensity in the same way as current. You should therefore avoid overcharging by using a charge controller or moving to a lithium battery.

Charge controllers dont have their own inbuilt power supply, and the system relies on battery voltage to function. These chargers must therefore be connected to the battery before connecting to the solar panel itself.

Once connected, the charger will display battery voltage. At this point, you can connect the charger input terminals to the solar panel.

You May Like: Duralast Gold Battery 35 Dlg Group Size 35 640 Cca

Can You Use A 24v Solar Panel To Charge A 12v Battery

Yes, but not directly.

In general, you cant simply connect a solar panel to a battery, as this can cause the battery to overcharge, which can permanently damage the battery.

So in order to protect your battery, you should connect a charge controller between the solar panel and the battery.

This controller will convert the 24v solar panel output to a more suitable 12v, so you can safely charge your battery without risking permanently damaging it.

Related article: Can You Overcharge A Battery With A Solar Panel?

How Long Will A 100w Solar Panel Charge A 100ah Battery

400W off Grid Solar Kit: 4pcs 100W 18V poly Solar power Panel &  100AH ...

A 100-watt solar panel is relatively smaller in the solar market, making it easy to transport and install. Therefore, they are popular at campsites, RVs, and off-grid activities.

However, since a single 100w panel can only produce 30Ah of power daily, it will take 5-6 hours of peak sunlight to charge the battery. If you are camping, your power needs may be 80Ah, which means one 100w panel will not be enough to charge the battery faster under average weather conditions.

Two or more 100w solar panels may do a better job, or you can buy a 300-watt solar panel. Intensive energy consumption activities such as air conditioners or extended days of off-grid camping may require as much as 1800w of solar panel power.

You May Like: Tesla Model 3 Battery Cost

What Are The Different Types Of Deep Cycle Batteries

Youll want to pay attention to the chemistry of your deep cycle battery as it will impact how effective the battery performs. There are two types of 100Ah deep cycle batteries available from Batteries Plus: Lead acid and Lithium Iron phosphate . The key differences between the two are performance and price. LiFePO4 batteries will cost more upfront, but run longer, recharge faster and have much longer lifespans. For more information read The Complete Guide To Lithium Vs Lead Acid Batteries from Power Sonic.

What Size Solar Panel Is Needed To Charge A 100ah Battery

We may earn a commission if you click on a link, but at no extra cost to you. Read our disclosure policy for information.

So we have an important question asked by a lot of engineers about how to charge and what sizes of solar panels are needed to charge a 100Ah battery.

Before we head to the original question at hand, let us discuss what solar panels are and why is it more acceptable these days for more electricity generation.

It is claimed that solar panels can generate a lot of electricity and are environmentally friendly.

If we look at other sources of electricity generation, nuclear plants are really harmful, if something goes wrong may be catastrophic.

Oil/diesel generated electricity is not a sustainable source of energy either, which makes solar energy much more acceptable since its abundant by nature.

Solar electricity generation has seen rapid growth in usage, due to low carbon energy technology, and due to rapid improvements in technology, most people are shifting towards using solar panels for power generation.

Hydro and wind are alternate renewable sources of electricity generation.

However due to technological advances, solar energy harnessing is considered much better compared to the two, and is a decent addition to power generation that is green and sustainable.

Read Also: Chevy Bolt Battery Replacement Cost

Factors Affecting Efficiency Of Solar Panels

There are few factors that affect solar panel efficiency.

The main components are panel material components, reflectance efficiency and thermodynamic efficiency.

Panel material components

There are two types, monocrystalline and polycrystalline.

Monocrystalline components are usually efficient due to uniform composition, and tend to have better performance in unfavorable conditions such as low light and very hot conditions.

Typically most home users have monocrystalline panels.

Polycrystalline material however has fragmented composition, which is a cause for lower efficiency. But they are cheaper than monocrystalline panels.

Reflectance Efficiency

Reflectance efficiency is basically how much sunlight is reflected by the panel, the lower they are reflected, the better the efficiency of that panel.

The more sunlight is absorbed for use, the better in this case, so less reflection on solar cells means better.

Thermodynamic efficiency is the highest efficiency that a panel can reach.

Its the ability of the panel to use a significant amount of sunlight and convert it to electricity after excluding the loss of energy as heat.

What Size Solar Panel Do I Need To Charge A 100ah Battery

DIY Solar | Sizing an Off-Grid Solar Power System | Battery Sizing

First, I would want to know How much battery capacity has been used? If I know how much amp-hours have been taken out, or discharged, then I will know the amount of energy I have to put back in and size the solar panel accordingly.

I have never discharged a lead-acid battery 100% that would be unheard of, unless it was unavoidable.

Some lithium-type batteries can be almost emptied, but lead-acid cells should only be discharged between 20% to 80%, depending if they are normal car-type batteries or deep-cycle design.

Im going to talk about lead-acid batteries for the purposes of this post, as they are the most common type in use. In the lead-acid category there are two kinds of lead acid cell design.

In general, a 100Ah deep-cycle lead-acid battery would require 180 watts of solar panel to fully recharge from 50% Depth of Discharge assuming 4.2 peak-sun-hours per day. It would take 8 hours to fully recharge with a clear sky.

Recommended Reading: What Auto Stores Carry Interstate Batteries

How Do I Find Out My Battery Capacity

Battery capacity is normally clearly stated on the packaging and container.

In lead-acid batteries, it is also indicated by C with a number giving the C-Rate, the number of hours in which the power contained can be delivered.

For example, if you see a description of C20=100Ah, this battery can deliver a total of 100Ah if it is discharged in 20 hours. Lead batteries are often C20 by default.

With a faster discharge, the total battery capacity drops radically. For example, if you disconnect in 5 hours, it will only deliver 70Ah.

This is because the internal resistance increases when the battery is discharged faster, and heat loses capacity.

How To Work Out The Size Of Solar Panel You Need

It is actually pretty simple. You just need to know three things:

  • The average amount of sunlight in the day
  • The voltage of your battery
  • The AH of the battery

You already know the second two pieces of information. You likely have a 12v battery, and it has a capacity of 100ah.

This means that you only need the third piece of information. This is the average amount of sunlight per day.

This will be the hours where your solar panel should be receiving the full amount of power. On average, this should be about 5-hours per day.

This means that we only have 5 hours a day where we are able to give the battery all of the juice that it needs.

This means that we need to be getting 100-amps over the course of 5-hours. Sure, there will be times outside of this where the battery will be receiving a trickle charge, but we cant rely on that.

We divide 100 into 5. This means that we need to supply 20-amps per hour to the battery.

We now take this 20 and multiply it by the voltage. This means that, at minimum, we need a 240-watt solar panel to provide all the power that the battery requires to full charge.

We suggest that, at minimum, you get a 300-watt solar panel. This will help to account for any drop-offs in power throughout the course of the day.

We suggest that, at minimum, you get a 300-watt solar panel. This will help to account for any drop-offs in power throughout the course of the day.

How to Size your Solar Power System > > Check out the video below:

Also Check: Best Battery For Dump Trailer

Related Posts