This question falls into two parts:
- How long does an electric wheelchair/scooter battery last before it needs to be replaced?
- How long does an electric wheelchair/scooter battery last on a single charge?
We’ll cover both in this article.
How long does an electric wheelchair/scooter battery last before it needs to be replaced?
There is a great deal to consider when talking about the total life span of a wheelchair/ scooter battery, but as a general rule of thumb a new battery should last at least six months. However it can last as long as year or even longer if properly maintained using the tips below.
Don’t heavily discharge the battery
To get the most out of your wheelchair/scooter battery, it should be fully recharged daily. Doing so can extend the life of your battery by almost double because you are reducing the depth of each discharge and recharge cycle.
For example, if you discharge the battery by 50%, but then fully recharge it that day it will last longer than if you discharge the battery by 75% over two days before recharging.
In other words the shallower the discharge / recharge cycle the longer the battery will last. In jargon terms – the greater its cycle life (how many times it can discharge and recharge) will be.
The graph below shows an example of this concept on the BatteryGuy BG-640 6 Volt 4Ah lead acid battery. (Every battery has its own graph. If in doubt, ask the manufacturer of your battery for their data.)
Allow enough time for the battery to fully recharge each day
One common issue with wheelchair/scooter battery maintenance is that users do not actually fully recharge it daily. An 8 hour overnight charge is usually not enough to return the battery to fully charged. Each day they take the battery to a lower State of Charge dramatically reducing its cycle life due to sulfation (a crystal build up on the plates) or acid stratification (acid settling at the bottom of the battery case). Both occur in batteries which spend a great deal of time ‘partly charged’.
This has been noted in real life situations. Golf Carts which use a similar design to electric wheelchairs and scooters are known for using the same batteries, but achieving total life spans up to twice as long. Much of this has been put down to the longer periods of time they spend on charge each day.
Should you find that in practice there is never enough time to fully recharge the battery before the electric wheelchair/scooter is needed again, then investing in a second battery or battery pack can make a great deal of financial sense in the long term.
Use a quality charger
The exact time a battery needs to fully recharge depends on use, battery age, the ambient temperature of the room and the charger itself. For this reason investing in a quality charger that will display the State of Charge will help you see when your battery is truly fully charged.
The most basic battery charger will simply pass a constant charge over your unit, but has the following disadvantages:
- It’s slower because it misses the opportunity to apply a greater charge when possible
- It has the potential to overcharge and damage the battery unless disconnected at the right moment
- It can misinterpret a completely discharged battery as a dead battery
Many electric wheelchair/scooter owners invest in a quality battery, but cut costs on the charger. This is a false economy because bad charging damages the battery.
A good charger (such as the Genius G7200) will typically move through three stages and switch itself off when the battery is fully charged. It will also apply a small trickle charge every time it senses the battery is falling below 100% charged.
If possible, keep the battery at room temperature when in use and when charging
The ideal operating temperature of an electric wheelchair/scooter battery is at a room temperature of 77° F (25° C). The actual capacity of the battery (how long it will last on a single charge) as well as its ability to take a charge will decreases in both lower and higher temperatures.
Obviously when in use outdoors it is not always possible to keep batteries at their ideal temperature, but making sure the room where your electric wheelchair/scooter is stored and where the battery is charged is kept at 77° F (25° C), rather than say a cold garage, will go a long way to increasing the total life of the unit and decrease the time it takes to recharge.
It is also worth noting that batteries do not like extreme heat, so storing or charging them in, for example, a hot garage will also reduce its total lifespan.
Keep the battery at room temperature and the charge topped up when not in daily use
If you don’t plan to use your electric wheelchair/scooter for some time (a week or more) the same storage advice as above remains. Keep the battery at room temperature in a dry environment.
Even in these ideal circumstances all batteries self discharge. At low levels of charge, crystal build up (known as sulfation) on the internal plates and can cause irreversible damage to the unit. As such, a top charge every two weeks is recommended. Alternatively, permanently connect the battery to a smart charger (see above) which will apply a charge as and when it is needed.
How long does an electric wheelchair/scooter battery last on a single charge?
If you have read the above recommendations on maintaining your battery in ways to maximize its total lifespan, it will now be clear to you that this is a bad question! To totally discharge a battery is a sure fire way to dramatically reduce its lifespan.
A better rule of thumb is to ensure you have a battery that for your daily requirements does not drop below 70% state of charge and that you are able to allow enough time for a full recharge overnight.
To measure the state of charge of your battery at the end of a normal day first:
- Let the battery rest for a few hours, no discharging or recharging – recent use can affect results so also check there are no electric wheelchair/scooter components still operating. If unsure, disconnect the battery completely by following the manufacturers instructions.
- If the battery has been in use in very cold or hot temperatures, bring it into a room where the ambient temperature is around 77° F (25° C) and allow several hours for the entire battery to reach that temperature.
Now use a voltmeter to measure the voltage between the terminals.
The terminal voltage on a battery at 70% state of charge should be around 5% above the stated voltage of the battery. So for a 12 volt labeled battery you should see a voltage of around 12.6V.
If the voltage you see is substantially below this, especially if it is below the stated voltage of the battery (in the case above this would be below 12 volts) you are heavily discharging your battery and dramatically decreasing its lifespan.
Consider instead a second battery, ways in which you can recharge during the day, or a higher specification battery that reflects your requirements. If in doubt, contact the electric wheelchair/scooter manufacturer for their advice.