How Do Rechargeable Solar Batteries Work? [How Do They Charge Electricity?]

If you’re looking to truly make the most of a solar panel array, unless you’re planning on hooking it up directly to electronics for some real-time energy action, you’re going to need a rechargeable solar battery.

Solar batteries are essentially your power hub; they provide a destination for your energy yield to hang out until you’re good and ready to use it — amazing, right?

It’s insane how far power storage technology has come in recent years, especially in the solar field.

The mind boggles at the potential of these high-tech solar storage units, but your brains shall boggle no more, as I’m going to tell you exactly how they work. Let’s dive right in!

How Are Solar Batteries Charged Using Solar Power?

In terms of charging, a solar battery doesn’t work any differently than a standard rechargeable battery.

It doesn’t have to do any energy conversions, as the solar panels themselves take care of business in that department.

All a solar battery does is receive solar energy that has already been converted into a DC electrical current, and the reason they can be recharged time and time again is that they’re what are known as secondary cells.

All batteries use a chemical reaction to generate power, and for primary cells, this can happen until the chemicals are finished reacting, i.e. single-use batteries.

In secondary cells, on the other hand, this chemical reaction can simply be reversed, priming it to occur again and again.

How Do Lithium Ion Batteries Solar Batteries Work?

As they’re the most popular and high-performing solar battery technology, let’s begin our battery bonanza with the lithium ion blueprint.

Lithium ion is actually an umbrella term for a number of different battery technologies, but although they go about it in different ways, they all use the same core principle of power storage.

It all starts with a chemical reaction involving lithium ions releasing free electrons, thereby creating chemical energy.

To convert this chemical energy into electrical energy, a facilitating medium known as lithium-salt electrolyte is used to get the aforementioned electrons to flow from the negative anode to the positive anode.

Lithium-salt electrolyte is a liquid that runs through the core of a lithium battery.

It provides positive ions to get the electrons moving and eventually to whatever electronic you have attached to the battery.

Then, when receiving power from the solar panels, electrons are drawn back to the starting point, enabling further chemical reactions.

Historically, lithium ion batteries have been quite unstable, but those found in modern solar panel networks have sophisticated electric systems in order to stabilize and optimize them for receiving electricity derived from solar energy.

Lithium Vs. Lead-Acid

The second most common solar battery technology is lead-acid.

They can’t hold as much power as their lithium ion counterparts, nor can they hold it as long, and they have an inferior DoD too.

DoD, or depth of discharge, refers to the threshold at which a battery must be recharged.

A battery with an 80% DoD, for instance, will need to be recharged before it loses 80% of its power. 

Lithium Ion

As mentioned above, lithium ion batteries can hold more energy, keep hold of it for longer, have a more robust DoD, and are generally a lot smaller than lead-acid batteries.

The only issue is that these benefits don’t come for nothing, so prepare your wallet for a hit if you choose to go the lithium route.

Lead-Acid

With less power potential, a larger footprint, and a shorter overall cycle life, the lead-acid solar battery is on its way out, but that’s not to say you should discount them.

We’ve relied on this battery technology to power our cars for decades, and you can find high quality variants for comparably cheap prices.

What’s The Difference Between AC And DC Coupled Storage?

As I’m sure you’re aware, electrical current can either be AC (alternating current) and DC (direct current), and “coupling” simply refers to how your panels are connected to your solar battery.

Solar panels produce DC current (great) and solar batteries can only store DC current, (fantastic!), but before you can use this energy in your home (or out and about), it needs to be converted to AC (dang!).

With this in mind, there are two possible approaches to solar installation: DC coupling or AC coupling.

DC Coupling

This is your standard setup — sun comes out, solar panels suck some light in, convert it into DC current, pass it on to your battery, then, on its way out of the battery, it’s converted into AC for practical application.

As the current is only converted once, this is thought to be the most efficient means of harvesting and using solar power, but the catch is that installation is more time-consuming, complex, and costly.

AC Coupling

Between the panels and the battery connected with AC coupling, there is an inverter that converts the DC energy coming from the panels into AC so it can be tapped in real-time to power your home.

Excess energy can be sent to the battery, but first it must pass through a second inverter to get the DC makeover and make it storable.

When that power is eventually drawn from the battery, you’ve guessed it… it has to travel back through the inverter to make it usable AC current.

Obviously, three conversions take their toll on power efficiency, which isn’t ideal, but the benefit of an AC system is that your battery can draw power from the grid so you have a home backup whether your solar panels are performing or not.

AC coupling can also easily be retrofitted into established solar systems, whereas DC coupling cannot.

How Do Hybrid Inverters Fit In With All This?

Hybrid inverters contain both panel and battery inverter technology, meaning you don’t have to have multiple inverters in your system.

This one bit of kit takes care of all your inverting needs!

But the real reason they’re becoming such a hot ticket as of late is their expandability.

You can have them installed on a battery-less system, allowing you to use solar power in real-time in your home, but the option to add a storage solution after the fact is always available.

What Part Do Solar Charge Controllers Play?

Batteries are fickle devices. They like stability, especially when recharging, so how does a fluctuating power source such as solar get the job done?

Charge controllers, that’s how.

Charge controllers are the middlemen between your panels and your battery.

They receive the current, organize it into a stable flow, then pass it on to your battery.

They protect your battery from both low and high voltages, whilst also preventing back-feeding, which is where power is leached from your battery during panel inactivity.

If you need one, I highly recommend this EPEVER MPPT charge controller, but if you’re pulling the purse strings tight at the minute, something like the Renogy Rover will be just what the doctor ordered.

Final Thoughts

There you have it — solar batteries may seem like incredibly complex devices, and, to a certain extent, they are, but their function is not dissimilar to typical rechargeable batteries.

Whereas standard battery chargers plug into a wall outlet to convert AC into DC and re-juice the attached batteries, a solar battery simply plugs into a charge controller and receives a ready-made DC current — no conversion necessary.

The only exception to this would be AC coupled systems in which the current has to be converted twice before it reaches the battery.