In the last decade, cordless tools have expanded in voltage and application to become primary work tools on residential and commercial job sites. It's all because of the batteries.
Batteries are the backbone of the solar revolution. Fuel Ghoul notes that here in Toronto Canada, there are quite a few different service companies claiming to be 100% sustainable and new batteries with improved power storage technology are the keys to their success.
EcoDeckBuilder uses ‘solar powered’ cordless drills and chop saws to cut and join lumber (that has been ecologically sourced), and Ecocut Lawns offers ‘zero emissions grass-cutting using Greenworks lawn gardening power tools with lithium batteries.
Raymi Toronto reports that Ecocut Lawns used to haul around all their commercial lawn care equipment in a high tech solar powered trailer on which there was a solar panel that would recharge their batteries in between jobs, but they learned after reviewing the data that simply by hauling this thing around, (when all their gear would otherwise fit comfortably in the back of a pickup truck), they were costing themselves more in terms of fossil fuel consumption, than their apparatus saved them in solar power.
Here's a picture of a solar trailer my buddy made from scratch to charge his lawn care appliances,
Pictures of the grasscutting rig are up on Greener People thread. This is one more service industry that has been affected by the introduction of lightweight, durable, rechargeable Lithium ion battery technology.
A Brief Discourse on Batteries
In engineering, the term ‘battery’ refers to a device for making electrically charged atoms (ions) travel from one point to another through a power system. When electrical charges move, they create an electric current and it is this flow of ions that ‘powers’ things connected to the battery. Batteries are based on ionic chemistry. The chemistry of how elements and molecules take up / lose valence electrons to become charged / uncharged ions, and how ions are central to molecules and elements being able to dissolve into polar liquids (electrolytes), like acids, bases, and salts dissolved in water.
To physically make a battery you need two electrodes between which the ions will travel and in the middle of the cell, you need a substance for them to travel through, which is called an electrolyte. One electrode, called the anode is negatively charged. The other pole that’s positively charged is called the cathode. When the battery is discharging—i.e., when it’s connected to a device that draws power from it—positively charged ions shuttle from the anode to the cathode creating a current.
Photo source --- Popular science graphics on GM Volt battery (2008)
If you are looking at rechargeable batteries, just imagine plugging the device into a wall socket and pumping electricity back into the cells forces the ions in the electrolyte to shuffle back to the anode, where their potential energy is stored until needed again.
Almost everything in battery design comes down to the materials of which the device has been constructed. What is the anode made of? What is the cathode made of? And what is the chemical composition of the electrolytic medium in between? This chemistry determines how many ions the battery can store, and how fast it can pump them out as raw DC (direct current) power.
The lead–acid battery was invented in 1859 by French physicist Gaston Planté and is the oldest type of rechargeable battery. Lead-acid batteries use Pb lead for the electrodes, and sulfuric acid H2SO4 is the electrolytic medium. Despite having a relatively low energy-to-weight ratio, and a low energy-to-volume ratio, its ability to supply high surge currents means that the cells have a decent power-to-weight ratio.
These features along with their low cost makes lead acid batteries attractive for use in motor vehicles which require a robust charge to start the internal combustion automobile engine. The modern starter motor needs a sustained 12-volt charge. The lead acid battery is not a very practical choice for portable equipment. I couldn’t imagine running a weed whacker or a cordless drill with a lead acid battery attached, as it would be heavy and dangerous.
Nickel Cadmium Batteries Versus Lithium batteries
The first Ni–Cd battery was created by Waldemar Jungner in Sweden in 1899, and like so many other electrical pioneers he had a patent dispute with the Edison Corp in the early 1900s which many people now believe Edison won only because he had greater financial resources to devote to the case.
The nickel–cadmium battery, NiCd battery or NiCad battery is a type of rechargeable battery using nickel oxide hydroxide and metallic cadmium as electrodes. The abbreviation Ni-Cd is derived from the chemical symbols of nickel (Ni) and cadmium (Cd), and interesting note - the abbreviation 'NiCad' is actually a registered trademark of SAFT Corporation which I believe is a direct descendant of the company that Jungner founded one hundred years ago.
Lithium Ion batteries were created at about the same time but it wasnt until the 1970s that breakthroughs made by Exxon funded labs made them feasible. Lithium ion has various formulas There are hundreds of formulas of lithium ion, each with various features and benefits.
Last decade, lithium-ion batteries gave transistor legs. Without the newly conceived lithium ion batteries developed by Exxon we would not have smartphones, tablets or laptops.
Lithium ion batteries do not necessarily bring more power to the job. Battery chemistry does not influence power - this calculation is determined by the voltage of the battery and the efficient design of the motor, transmission and mechanism at work. Increasing both or either voltage or efficiency increases power. An 18V lithium ion battery has the same potential to deliver power as an 18V NiCd battery because they are the same voltage. However, the ergonomic advantage of lithium ion batteries allows manufacturers to make higher voltage tools-and, thus, increase power-without increasing weight.
Lithium ion does not mean more run time The run time (or number of holes drilled on a single battery charge) is determined by three factors: 1. Battery voltage 2. Battery capacity (amp-hour) 3. Efficiency of tool design Increasing voltage, amp-hour or tool efficiency improves run time. NiCd and NiMH batteries range in capacity from 1.3Ah to 3.0Ah. In comparison, lithium ion batteries range from 1.1Ah to 3.0Ah. The lithium ion battery is smaller in size and lighter in weight than a nickel cadmium (NiCd) or nickel metal hydride (NiMH) battery. In addition, lithium ion has virtually no self-discharge. This allows a lithium ion battery to be stored for months without losing charge.
Remember, amp-hour is only one factor in run time, just as the size of the gas tank is only one factor in how far a vehicle can drive on a tank of gas. The best measure of run time on a cordless drill would be how many actual holes are drilled on a single charge, or how many boards were cut on a single battery. But even using these true metrics, the applications per battery charge factor in voltage, capacity and the efficiency of the tool and operator.
Its also worth noting that there currently is no industry standard for measuring the amount of recharges a user can get from the battery.