How does a solar battery work?

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How does a solar battery work?

How Do Solar Panels Work in a Solar Power System?
An off-grid solar power system actually works quite simply. You need solar panels, a charge controller, and a battery. That's all there is to it... and yet, there's more to it than that.

If we delve a bit deeper to understand how solar panels work in detail, there are many things that need to be in place, both to make it work and to make it work well.

How Do Solar Panels Work Fundamentally?

A solar panel converts light into direct current (DC). The more light there is on the solar panel, the more power it produces. The power ratings indicated on a solar panel show how much power the panel can produce when the sun shines directly on the solar cells and not from the side or above (a solar panel is composed of several solar cells in series connection). So, it's a figure that's only accurate when the sun is shining its best, and the solar panel is positioned at the correct angle to the sun.

When it's heavily overcast, a solar panel's output falls to 0-10-20% of the rated power. That's why you need a battery that can store energy from sunny days for use during rainy ones. In terms of daily power production, solar panels will produce the most in July (on a standard year).

Season for Solar Panels?

Therefore, it's necessary to determine during which time of the year you'll need solar power. On a boat or a caravan, it's often only for summer use, making solar panels a good solution. But if you also need power in winter, you'll either need a lot of solar panels and a large battery or you'll need to find an additional power source.

Shading on Solar Panels

Is it significant if there's a little shade on the solar panels? Yes, it's very significant, because a solar panel is composed of solar cells in series, and no chain is stronger than its weakest link. So, if there's shade on one solar cell, it pulls down the rest of the solar cells in the chain.

To avoid shade on one solar panel affecting others, it can be smart to connect the panels in parallel (there may be other reasons why you need to connect serially or in parallel), so shade on one panel doesn't ruin the entire production, but only the production for that one panel. On the other hand, there may be an advantage in having the panels in series, as the voltage rises to a production level faster in the morning (requires MPPT charge controller) and lasts longer in the evening. But it requires that no shadows fall on the panels at all.

Here's a video with a test of what shadows do to solar panels and whether you should choose serial or parallel. You can use the video to make your decision. However, it's by no means scientific 🙂

Angle to the Sun

Ideally, the solar panel should face directly towards the sun at all times, but they rarely do so in practice. It requires mechanical devices that move the solar cell throughout the day, which is rarely cost-effective.

So, to get as much as possible out of the solar panels, they should face south, and the optimal angle in relation to horizontal depends on where you are in the world.

What Does the Charge Controller Do?

How do solar panels work with the charge controller? The charge controller is there to protect your battery. There's the possibility of connecting very small sizes of solar watts directly to a battery, but we'll always recommend that you use a charge controller. In over 98% of cases, it's absolutely necessary!

If the charge controller is of good quality and of the best technology (MPPT), it will be able to get more power out of your solar panels while also charging your battery adjusted according to the charge status of your battery. So, it's important that you choose a good charge controller, as it will yield a greater return and your expensive batteries will last longer.

The charge controller also often ensures that you don't discharge the battery more than it's sized for and ensures that no current flows back to the solar panels at night.

Solar Batteries

The battery is an expensive part of your system, and you can ruin them quickly or you can take care of them and have them for 10 years.

Without going into deep battery details here, as you can read elsewhere on this page, it's generally important that you choose a battery type that suits your usage pattern.

Roughly speaking, there are starting batteries like those you know from your car/boat, which need to be able to deliver a high starting current for a short period, and then there are deep cycle batteries, which can deliver a lower current over a long period. These deep cycle batteries are typically used in connection with off-grid systems.

Deep cycle batteries have the advantage that they can be discharged by 50% without suffering significant damage (however, we recommend not discharging more than 30% in daily use), whereas starting batteries suffer damage already after a 10% discharge.

Lithium-ion batteries can be discharged even more, but are, on the other hand, more expensive.

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