Cordless power tools - batteries: the basics

Vince Braunsin Battery/Electric Power

The cordless outdoor power tools market is changing fast, with environmental footprints moving higher up the priorities list for many organisations, along with increased EU legislation. Gardening, landscaping and grounds professionals are looking for cleaner, quieter and safer alternatives to the typically used petrol-chugging machinery.

Vince Brauns, European Product Manager at cordless outdoor power equipment specialist EGO Power Plus, explains the evolution of battery technology, the technology's basic principles and why there is no better time than the present to adopt battery power.

In a world of professional landscaping and grounds maintenance, petrol has been the fuel of choice for over 100 years. The reason being that, up until now, there has been no viable challenger that delivers equal measures of convenience, power and performance.

No viable alternative

One of the huge barriers in uptake of battery power tools is the misconception that the tools simply won't provide enough power or run time to complete a job, which in years gone by, may have been the case. Even though the harmful emissions from petrol power is known, the need to get jobs done quickly and efficiently have, in the past, always outweighed the negatives.

Governments the world over are having to find alternatives to fossil-fuel powered transport, power and heating in a last-ditch attempt to save the planet. It's time that the same level of urgency is applied to outdoor power tools.

Battery power reimagined

In addition to reducing their environmental footprint, many in the grounds maintenance and landscaping industries are realising the disadvantages of petrol in noise pollution, cost and health risks of both the emissions and vibration associated with petrol.

It wasn't until 1991 that the world woke up to the power of lithium-ion, however continued research over almost three decades has enabled manufacturers like EGO to harness the best of lithium-ion and create tools that match and, in some cases, outperform their petrol counterparts.

While upfront cost, charging time and battery deterioration also remain a concern for professionals that are apprehensive about making the switch, understanding the evolution and capabilities of battery power is massively important. Knowledge is the next crucial step in changing attitudes and proving why battery power tools are a preferred and future-proofed solution for a wide range of outdoor applications.

Knowledge is power

When choosing battery tools, it's important to ensure the battery can consistently deliver power for the application required. Power is measured in watts (W) and is calculated by multiplying voltage (V) and current (A). To work out how long the power can be delivered, users need to multiply voltage with capacity (Ah) to find out the energy in watt-hours (Wh).

It's the relationship between voltage and current that counts though. A big voltage doesn't necessarily mean big power - there also has to be enough current (and vice versa). In the instance of battery-powered technology, the current depends on the cell types being used, the condition and quality of the cells and the control system put in place to manage them.

As a buyer, be mindful of battery labels that use watts instead of watt-hours or amp hours. This isn't as helpful because users don't just want to know how much power the battery generates in a given moment - they want to know how long it can deliver that power. Run time, however, can depend on many factors such as the capacity of the battery to begin with, which tool being used, how it is being used, how tools are taken care of, and how the batteries are stored.

The full circuit

A basic knowledge of circuits will also help you choose the kit with the best bang for your buck. When battery cells are connected end-to-end in a single row they are in 'series'. Arranging cells together in series delivers the required voltage (V). When more than one series is combined, the rows of battery cells are connected in 'parallel'. Adding an identical number of cells in parallel delivers more capacity and run time (Ah). The batteries have been designed to deliver 56V for an extended period of time in order to meet user expectations. To achieve this, we arrange the right number of cells in series to deliver 56V - then increase capacity (Ah) by adding more cells in parallel: (W) Fig. 1a.

Theoretically, a manufacturer could build a battery with more power than a user would ever need for outdoor applications. This is where manufacturers must apply a balancing act between power and usability. More cells mean more weight and size. That's why EGO has settled on a 56V platform. We have found 56V provides the optimum balance between petrol matching performance and run-time.

Left: BCX3800 line trimmer and brushcutter Right: Fig. 1a

Quality over quantity

Cell consistency is also critical to battery performance. Inconsistencies could lead to over-charging and discharging, which can impact battery lifecycle and create potential safety issues. When selecting the right manufacturer for battery-powered tools, look for a brand that uses high-quality cells and a company that continually assesses the market to ensure the best quality.

In addition to sourcing components from the world's leading suppliers, our tests and selects every single cell before building a battery. This includes testing and sorting each cell to ensure only those with the

most consistent voltage are used while monitoring and managing each cell during operation. Power is nothing without control which is why the Power+ 56V Arc Lithium battery is continuously controlled by software, microprocessors and power management systems.

Microprocessors and software within the battery monitor each cell for temperature and voltage to ensure that charging and discharging is managed in a balanced and controlled way with the other cells within the pack. This ensures each cell is performing optimally and prolongs the lifetime of the entire battery pack.

Managing heat

Managing heat is key to maximising performance. A battery gets hotter the longer it's used and, the more power it generates, the more heat is released. Too much heat and the battery will shut down for safety. Heat also degrades cells over time, reducing battery life. That's why batteries must be cooled effectively to increase performance run time and battery life. EGO manages heat in three ways: mechanically, chemically and electronically.

Power pack

Mechanically - an arc cell design is used rather than the brick-shaped battery packs chosen by many other manufacturers which can be quick to overheat, causing a shutdown of the battery. The unique arc design increases surface area, dissipating heat more effectively. The design also means that cells are as close to the surface as possible allowing more air to pass over each cell to keep it cooler for longer periods. Lastly, the batteries are mounted to the outside of the tools allowing for quicker heat dissipation, meaning they can deliver longer-lasting power over manufacturers which have their batteries encased within their tools.

From a chemical perspective, each battery cell (up to and including the 5.0Ah battery) is surrounded by a unique phase change material (PCM) that absorbs energy and keeps individual cells at their optimum temperature for longer. The more heat the PCM absorbs from the battery, the more heat the battery can generate without overheating, helping to maximise run time.

Electronically, many manufacturers of battery-powered tools will use one or two sensors to monitor the battery's temperature. Typically, these are located on the cells that are most likely to become the hottest and some have even been known to locate them by the coolest cells. EGO recognises that cells can change after several charge cycles, meaning that these sensors can become ineffective by no longer monitoring the hottest cells.

To counter this, there are engineered sensors to monitor the temperature of all the individual battery's cells. By doing so, in the event of a cell reaching a high temperature, the entire battery will shut down until it cools down to within the optimum operating parameters. This not only ensures safe use but also extended battery life.

Left: Power Plus STX3800 trimmer Right: LBX6000 blower

How should batteries be stored?

Contrary to popular belief, the batteries don't require special temperature requirements for winter storage. All that is advised is that batteries aren't stored in direct sunlight or in a place where they can attract moisture.

The cost of evolution

Now that you have a basic understanding of battery technology and its role in the outdoor power tool market, you will probably have one more burning question; cost.

Upfront costs for the technology can be higher than that of your average petrol-powered tool. However, research investigated the total cost of ownership between petrol and battery-powered outdoor equipment over an extended period.

The test looked at the cost of a petrol brush cutter, hedge trimmer and leaf blower compared with their battery-powered counterparts. Initially, buyers would spend approximately £690 extra on battery-powered equipment in year one, however would see a turnaround in just their second year of ownership, making a total saving of £365. In years three and four, the real savings of ditching petrol begin to show themselves, with users saving a total of £1,430 and £3,500 respectively. By the fifth year, the test factored in a full replacement of all equipment and yet the savings amounted to a total lifetime saving of over £4,500! This is in large part due to the inexpensive cost of recharging a battery (typically well under 10 pence for a full recharge) compared to the cost of petrol, and also the lack of servicing required for battery powered tools.

With the additional environmental benefits of using battery technology, discover how your business could seamlessly make the switch to battery power at