Charge Your Garden Tools With Solar Power

Ongoing improvements to batteries have helped increasing numbers of gardeners to cut the cord—and the need for gasoline—for their string trimmers, edgers, lawn mowers and other gadgets. These days, in fact, you can even find heavy-duty equipment such as tillers, chainsaws and wood chippers powered with long-lasting rechargeable batteries.

Maybe you’ve already replaced some of your older gas-powered tools with electric or fully rechargeable, cordless models. To save money in the long-run—and go even greener—consider setting up your very own portable, solar charging station for your garden tools.

“In terms of having an off-grid charging center for your tools, that’s a relatively simple setup,” says EcoFlow’s Ryan Oliver, head of communications for North America. Established in 2017, EcoFlow specializes in portable power and renewable energy. “You can use a solar panel directly connected into a large storage battery and then with that large battery, the power station would be charging your individual [tool] batteries,” he says. “There’s enough capacity in these portable solar panels these days combined with putting that into a battery that you’re going be able to power a lot of outdoor tools.”

In some areas, professional landscapers have already begun transitioning to portable, solar systems to charge their garden tools. “There are rules being set up in local jurisdictions around the country banning the use of gas-powered, outdoor tools,” Oliver says. “So, you’re going to see landscapers actually installing solar arrays on their vans and using that to charge a battery system, which is ultimately going to charge the individual batteries that their tools require.”

Unlike large, permanent solar panels connected to the established electrical grid, portable solar panels and their connected battery packs are much smaller, less expensive, and can be operated independently from the electrical grid for ease of charging things like garden tools on the go. “A lot of our stuff is used by campers and outdoor enthusiasts,” Oliver says.

While older panels are large and rigid, many new solar panels are designed to be more mobile. Some even collapse for extra portability. Nevertheless, when establishing your a solar charging station for you garden tools, Oliver says, “The idea is you would keep your solar panel and the portable power station in an area where it’s not going to move much.”

That could mean mounting the solar panel outdoors and sheltering the connected battery pack inside a nearby barn, garage or greenhouse. (Incidentally, the battery pack itself doesn’t take up much space. A 250-watt, portable battery pack is typically about half the size of a toaster. A much larger, 3,600-watt battery is roughly the size of a desktop computer.)

If you’re the DIY type, you can choose the individual components, including a solar panel, battery pack and inverter on your own. (An inverter is a piece of equipment that converts the direct current power coming from the solar panel into the alternating current power used by the various devices you charge via the battery pack.)

For their part, solar panel costs can vary widely, depending on factors such as physical size, capacity, portability and more. “You’re typically looking at, say, $300 for a 110-watt, which may be enough if you’re not using the battery every day,” Oliver says. “On the higher end, you’re looking at $1,000 for a rigid solar panel…. That’s a 400-watt system.”

“In terms of [battery] prices, the industry average is about a buck a watt,” Oliver says. That said, not all batteries are created equal. Not to be confused with lithium-ion batteries, the newer lithium iron phosphate batteries can last three to five times longer than older battery technology.

“If you are using lithium iron phosphate, you can actually get several thousand discharges,” Oliver says. “Older lithium-ion batteries … tend to get around 400 to 600 discharges over the lifespan of the battery before the battery can no longer charge to 80 percent.

“There’s also an advantage for lithium iron phosphate being able to charge faster. These large batteries can charge in under two hours. With the traditional material, you may be looking at eight hours for a charge.”

If you prefer a more plug-and-play option over hand-picking your own components, prepackaged, portable solar-powered charging stations with built-in inverters are also available.

“A beginner 200-watt ‘suitcase system’ with 100-amp-hour battery and 700-watt inverter begins at under $1,000, pretax,” says Yi Li, founder and CEO of Renogy. Around since 2010, Renogy sells off-grid solar energy components and systems. “A portable, all-in-one unit with 200-watt solar panels begins at roughly $1,500,” Li says.

Just how large should your solar panel-and-battery system be for your garden tools? To be able to answer that question, Li says, “Users should become more aware of how and when they use electricity and become comfortable using watts and watt-hours.”

You can boost your watt-hour awareness by taking stock of the various gadgets you plan to operate. “You would want to calculate how many [individual tool] batteries you have to charge for your tools and what size batteries [they require],” Oliver says.

You can determine the watt-hours an individual tool will use by multiplying its volts and amps. “Say a typical battery in a lawn mower … is a 7.5-amp battery and 56 volts,” Oliver says. “So, it’d be 56 times 7.5. If you want to charge just that battery alone, you’d be looking at 420 watts.”

Likewise, you should think about how often you’ll need to access your battery power. For instance, if you only plan to use the system to recharge the batteries for a few small tools that you use once or twice a week, you can likely get by with one of the smallest off-grid systems available.

But how about something larger like that cordless lawn mower? If you have a large area to mow, if you mow really frequently, or if you have multiple mowers, you might need a battery with a much greater capacity. “If you’re having several tools that you’re trying to charge, you would probably want something more in the 2,000- to 3,600-watt range,” Oliver says.

When calculating your battery capacity needs, don’t forget about any new gadgets you may have your eye on. “There may be additional tools you’re planning to buy in the future that you should factor into your calculations, so you’re not buying one battery that’s too small for your use case,” he says.

You’ll also need to consider the amount of sun your specific location gets. A resident of sunny Phoenix may be able to store power more often and more consistently than residents of cloudier spots such as Seattle or Portland. That means the Phoenix resident might be able to get by with a less expensive, smaller capacity battery.

“Going off-grid solar means electricity is only created when the sun is shining, so users will likely need to depend on their stored energy (watt-hours) in batteries,” Li says. “In addition, it is important to consider whether you will expand later or just use the bare minimum.”

Failure to do so could necessitate upgrading to a bigger battery later—or buying additional batteries and “daisy-chaining” these as needed. “The nice thing about our portable or DIY off-grid systems is that they can be expandable whether it’s buying another unit or adding more batteries and solar panels,” Li says. “However, users should avoid expanding with dissimilar panels or batteries.”

In other words: Link only the same types of solar panels and only the same kinds of batteries. “If you expand your battery bank, it must be the same battery type and voltage,” Li says. “While on the subject of battery expansion, if you know you’re going to expand down the line, it’s best to get it done earlier [rather] than later.”

That’s because these specialized batteries naturally deteriorate over time. As such, you’ll get more bang for your buck by creating a bank of solar-fed batteries that are roughly the same age.

Of course, battery capacity is only half of the equation. “When you’re using these batteries with a solar panel, you’d want to be looking at the wattage that the solar panel puts out,” Oliver says. “You can kind of make a calculation about how much sun you get. Say you have a 200-watt panel and you’re like, ‘Well, I get an average eight good hours of sun.’ That’s putting out 1,600 watts of charge, if you’re actually getting full sun the entire time.”

No matter what type or size of solar-powered system you choose, “Keep batteries stored in relatively cool environments or at least away from direct sun or rain,” Li says.

And to maximize solar panel efficiency when charging garden tools, make sure its surface is as clean as possible. That includes clearing it of any snowfall during winter. Li suggests you install your solar panels in open spaces, away from shade or trees and tilt them towards the sun.

“If there is a way to have the panels move a little bit on your system, that’s actually helpful,” Oliver says. To soak up as many rays as possible, consider installing your solar panel on a swiveling post.

This article originally appeared in the July/August 2023 issue of Hobby Farms magazine.