When it comes to setting up solar panels to charge a battery, choosing the right size solar panel will not only stop you from forking out too much moola. It will also ensure efficient and effective charging of you battery. Here, we look at what size solar panel to charge a 200Ah (amp hour) lithium battery, for different charge times. You can get straight to the answer just down below. Or read on and in 5 minutes learn how to calculate solar panel size yourself. It’s easy. So lets do it!

What size solar panel to charge a 200ah lithium battery: TL;DR

No time to read on? Here’s the short answer to the question ‘What size solar panel to charge a 200Ah lithium battery’ (using Sydney as an example location).

You’ll need 650 watts of solar, or 3 solar panels, to charge your 200Ah battery within 6 hours. Here are the numbers:

If 650 watts is too much solar for you to afford, try a longer charge time.

Here is the cheat sheet table for solar panel sizes (in watts) to charge a 200ah battery for different charge times (at peak sunlight).

Solar Panel Size chart

These are solar panel size and charge time for a 200Ah battery, based on 100% solar output efficiency. However your panels will not typically perform at 100% in all conditions. So we also give you solar panel size for 70% solar output efficiency.

Keep reading for a table of typical dimensions for different size solar panels. So you can work out how much space you need too.

Now lets look at how you can calculate solar panel size for yourself…

Start With Your Lithium Battery Capacity

First, we need to know about your battery’s power. Expressed in Amp Hours it’s 200Ah.

But here’s the thing. Solar panels power output, is expressed in watts.

So to work out what size solar panels for a 200ah lithium battery, we first need to convert Amp Hours to watts. So we’re comparing apples with apples. Here’s how:

200 Amp hours to watts

The Wh (watt-hour) output of a 200Ah lithium battery depends on the voltage of the battery. Voltage for portable power usually comes in 12V, 24V and 48V. This is different to voltage in homes, which comes in 120V (USA) or 220-240V (Australia).

To help your calculations, we assume you have a 12 volt battery, as these are commonly used in RVs, camper vans, caravans and boats.

Assuming a nominal voltage of 12V, the watt hour output of the battery is calculated as follows:

So a 200Ah lithium battery with a nominal voltage of 12V has a Wh output or storage capacity of 2400Wh (2.4kWh).

What can a 200Ah lithium battery power?

Once you know the energy output of the battery, you can work out what appliances the battery can power. By way of example, a 200Ah battery could power a combination of these appliances (but not all of the them at the same time):

• LED light bulbs (8-10 watts each)
• Laptop (50-100 watts)
• Mobile phone and tablet chargers (5-10 watts)
• TV (50-150 watts)
• Small fridge (50-75 watts)
• Microwave (800-1200 watts)
• Toaster (800-1500 watts)
• Blender (300-600 watts)
• Coffee maker (800-1200 watts)
• Electric kettle (1000-1500 watts)

When it comes to charging a 200Ah lithium battery, next it’s important size the solar panel relates correctly for the battery capacity. Why? So we can get the battery charged up within a day.

What size solar panel to charge a 200Ah battery?

As we’ve mentioned, solar panel output is measured in watts. The higher the wattage, the more power the panel can produce.

Solar panels also come in different voltages. To use them together efficiently, match the solar panel voltage with the battery voltage.

So in this example, you’re going to have a 12V solar panel because you have a 12V battery.

If you want to know all about 12V solar panels, check out our post “What can a 12V solar panel power”. It’s the internet’s top 20 questions about solar panels all answered in one post!

Now back to calculating solar panel output.

When choosing solar panels for a 200Ah lithium battery, you want the right size solar panel to generate enough power to charge the battery to 100% in a reasonable amount of time.

This means selecting a solar panel with a wattage output based on the battery’s capacity.

The other thing to know about is how solar panels are sold. The typical size of a portable solar panel is 100 watts. You can also get larger portable panels of around 200 to 300 watts. Our Ecoflow portable panels are 220 watts for example.

You can connect panels together to get more power, up to a point. You’ll need additional equipment to do this.

So, lets work out what size solar panel will match well with your 200Ah battery’s capacity.

Calculating Solar Panel Size for a 200Ah Lithium Battery

To calculate the solar panel size needed to charge a 200Ah lithium battery, follow these steps:

1. Determine the amount of energy needed to charge the battery:

We calculated this above using the following formula:

Energy (Wh) = Voltage (V) x Capacity (Ah).

For a 200Ah lithium battery, the energy required to charge it from zero to full would be:

12V x 200Ah = 2400Wh.

2. Determine the amount of peak sunlight hours (PSH) in your location

Peak sunlight hours are the hours in a day when solar irradiance is at its peak (1000Wh/m2)

The amount of peak sunlight available is important because:

1. Solar panels only make power when the sun is shining
2. You need PSH to calculate the solar panel size required for your 200Ah battery
3. You want to be able to charge your 200Ah battery within a day.

The peak sunlight hours available will vary depending on your location, the time of year, and the weather conditions.

You can look up the average peak sunlight hours in your area with this US global solar radiation database.

Here is a table of the average peak sunlight hours for all Australian capital cities:

These values represent the average peak sun hours per day over the course of a year. The actual number of peak sun hours may vary depending on factors such as weather, time of year, and local shading.

For our example, we are going to use Sydney which has 5.3 PSH.

3. Get your answer: Solar panel size (in watts of output)

Our example is going to tell you what size solar panel to charge a 200ah lithium battery in 1 day in Sydney.

To calculate the solar panel size needed, you just divide the energy required to charge the battery (2400Wh) by the amount of sunlight available (in peak sunlight hours or PSH).

Remember, you found your PSH for Sydney in Step 2 above.

So, if you have 5.3 PSH available per day in Sydney, you would need solar panels with a capacity of at least 452 watts.

(2400Wh ÷ (5.3 hours) = 452 watts

Thats 2 x 200 watt panels and 1 x 50 watt panels – if your solar panels work at 100% efficiency.

Which they don’t.

Performance factors affecting solar panel size

When it comes to solar panel performance, it’s important to keep in mind that they typically don’t operate at full capacity. This will impact how quickly they can charge your 200ah battery.

There are several factors that will affect charging efficiency:

• Weather conditions: Cloudy or overcast weather can reduce the amount of PSH. Either you’ll need a larger solar panel size to compensate or you won’t be able to fully charge your battery in your timeframe.
• Technology efficiency: The efficiency of the solar panel and the charging controller can affect the charging time and the size of the solar panel needed.
• Panel orientation: The orientation of the solar panel can also affect its output, with panels facing directly towards the sun producing more power. Shading will also reduce solar performance.

So how do you accommodate for different local conditions and make sure you have enough power all the time?

If you can afford it, you upsize your solar panels.

Upsizing your solar panels – how big is big enough?

By taking the solar performance factors above into consideration, you can ensure that your solar panel system is optimized to deliver the best possible results.

Nominal capacity is just the rated capacity you see marked on the panel. 100 watts, 200 watts, and so on.

So lets get back to our Sydney example.

We know you need 452 watts to charge a 200ah lithium battery in one day (5.3 PSH) in Sydney.

At 70% efficiency, 500 watts of panels will give you 350 watts of power on average. That’s not enough to charge your battery in 5.3 peak sun hours, in Sydney.

650*.7 = 455 watts

Could you get by with smaller solar panel? Sure.

If 650 watts is too expensive, you could compromise on charge time, to reduce the solar panel size you need. And the cost.

Here’s how charge times impact the solar panel size you need:

What size solar panels do you need (in dimension)

Now that you know what size solar panel you need in watts, what about in dimensions?

To work out if you have the space available for the 650 watts of solar panel power you need, you can use this table below.

Here are typical dimensions for common sizes of solar panels:

It’s important to note that these dimensions can vary depending on the manufacturer and model of the solar panel. They just give you a rule of thumb before you settle on make and model for your solar panels.

What size solar panel to charge a 200ah lithium battery?

So lets get to the crux of it and answer the question in full – for Sydney:

In a Nutshell

Choosing the right solar panel size is crucial when it comes to charging a 200Ah lithium battery. And you can easily charge a 200ah Li battery in around 5 hours with 650 watts of solar panels. Reducing the watts will save money but also increase the charge time. By following the steps and using the free tables in this article, you can calculate the size of solar panel needed for your battery, no matter what size or model you buy. Remember to take into account any additional factors that affect the solar panel size, such as weather conditions, charging efficiency, and panel orientation. Applying a 70% efficiency rate to your solar panel will accomplish this.

FAQs