All-terrain power wheelchair: a buyer's checklist

An all-terrain power wheelchair is not simply a stronger indoor chair. The person buying one is buying the ability to cross a forest track, a gravel yard or a frosty field, and a specification sheet is only a rough guide to whether that will work. This checklist goes through the questions worth asking before a purchase, and it separates the numbers that can be compared from the ones that cannot.

Start from the ground you actually cross

Before reading any brochure, write down the surfaces the chair will meet in an ordinary week: loose gravel, wet grass, a muddy field gate, roots on a path, a ramp to the cabin, snow in winter. That list decides which numbers matter. Drive type comes first. A four-wheel-drive chair such as the FourX puts driving force on all four wheels instead of two, and Moventuras states an obstacle capacity of 130 mm for it. A figure like that is only useful if the test behind it is known. ISO 7176-10:2008 specifies test methods for determining the ability of an electrically powered wheelchair to climb and descend obstacles, and it applies to chairs designed for one person with a maximum nominal speed of 15 km/h or less. When comparing two chairs, ask whether the obstacle figure comes from that kind of standardised test or from a single demonstration. The first can be compared between manufacturers; the second cannot.

Tyres, ground clearance and suspension matter as much as the drive, and they are best judged on the ground itself. It is worth asking for a test drive on terrain that resembles home rather than on a showroom floor, and bringing along whoever helps with transport or charging.

Treat range as a comparison, not a promise

Range is the number buyers cling to, and the one most often misread. ISO 7176-4:2008 describes how to estimate a wheelchair's theoretical distance range from the energy measured while driving and the battery's nominal energy capacity. The test is run on a flat, hard, level surface at 18 to 25 degrees Celsius. The standard is open about the limits: its results cannot be used to derive an accurate range estimate for a particular wheelchair and occupant, because real range also depends on ambient temperature, occupant weight and distribution, terrain, surface type, tyres, and the age and charging history of the battery. The figures are meant for comparing chairs under similar conditions, much like fuel consumption figures for cars. Moventuras gives the FourX a range of up to 35 km. The words "up to" carry weight, and a sensible buyer asks what that figure means on their own tracks and in their own winter.

Cold deserves its own line in the checklist. A scoping review on winter mobility by Ripat and colleagues lists reduced battery power in cold weather among the barriers faced by people who use mobility devices. The chemistry explains why. A 2022 review in Materials by Luo and colleagues notes that below 0 °C lithium-ion batteries show capacity reduction, safety problems and a sharp decline in cycle life, mainly because lithium ions move more slowly in the electrodes and the electrolyte. Battery University lists a permissible discharge range of -20 to 60 °C for lithium-ion cells but a charge range of only 0 to 45 °C, with no charging permitted below freezing, because charging in the cold can plate metallic lithium on the anode and permanently degrade performance and safety. For a buyer this turns into a few questions for the seller: what battery type the chair uses, what the manufacturer says about operating and charging in frost, and where the battery can be kept warm and charged indoors.

Seat functions, weight and transport

Seating is where the chair meets the body. The FourX offers tilt, seat elevation and a standing support, and its stated weight capacities are 125 kg and 160 kg. Which functions a person needs is a question for the therapist or clinician who knows them, and nothing in a checklist replaces that assessment. What a buyer can do is ask which functions are available for the model, which can be added later, and whether the capacity leaves room for everyday load such as clothes, tools or a bag.

For anyone who will rely on a car, a bus or a specialised vehicle, transport is part of the same decision. The FourX has securing points that follow ISO 7176-19 and carries a CE marking as a class I medical device. For a chair that will travel in a vehicle, ask to see the documentation for both.

Many countries assess assistive devices through a public service, and in that process the need is easier to describe when it is concrete: the farm yard, the forest road, the distance to the nearest shop, the winter months. Rules differ from country to country, and nothing here is a promise about funding, so the first call belongs to the local assistive technology service.

Before you sign

A good purchase usually comes down to a handful of checks done in order: the surfaces the chair must cross, an obstacle figure from a standard test, a range figure read as a comparison, a plan for the battery in cold weather, and a seating and transport set-up that suits the person who sits in it. The standards and the physics are public. What remains is to ask the questions and to drive the chair on ground that looks like home.

Questions about the FourX or about how it would suit your terrain? Ask us more.

Sources

ISO 7176-10:2008, Wheelchairs, Part 10: Determination of obstacle-climbing ability of electrically powered wheelchairs. Catalogue entry

ISO 7176-4:2008, Wheelchairs, Part 4: Energy consumption of electric wheelchairs and scooters for determination of theoretical distance range. Sample pages

Battery University, BU-410: Charging at High and Low Temperatures. batteryuniversity.com

Luo H. et al. (2022), Lithium-Ion Batteries under Low-Temperature Environment: Challenges and Prospects. Materials 15(22):8166. doi.org/10.3390/ma15228166

Ripat J. et al., Winter mobility and community participation: a scoping review (RESNA conference paper, 2018). resna.org