Powerpacks and batteries for powered wheelchairs
Add-on Power Pack to manual weelchairs
Add-on power packs are used to convert a manual wheelchair into a powered wheelchair. Many wheelchair users like this solution because
- it allows them to pair a light, compact wheelchair with an electric drive system.
- they can usually be attached and detached from the wheelchair so it can be packed for getting in and out of cars or public transport.
As with regular powered wheelchairs, these can be controlled by the wheelchair user or by an attendant.
- removing the original wheels and replacing with modified wheels
- a battery pack
- a control unit adding electric motors to the wheel hubs adding a battery pack with its own set of wheels attached.
Some manufacturers also make power assisted powerpacks for manual chairs - you push the wheels in the usual way and the motors supply extra power.
Voltage, capacity and resistance
All powered wheelchair batteries are 12 volt and usually come in pairs, giving a total 24 volt output. Battery capacity is measured in amp hours (Ah). Most wheelchair batteries will have a capacity of around 50–75Ah. For most people, the capacity shouldn’t make much difference. More important is
the Internal Resistance, which determines how much power the batteries can deliver, especially at the end of the day when the charge is low. This should be as low as possible and ideally less than 3.0mOhm.
Types of battery
All wheelchair batteries are lead-acid batteries. Most commonly they’re of one of the dry types where the acid is contained in a solid (AGM – absorbed glass mat) or gel.
Dry acid batteries are:
- sealed so they can be transported and operated any way up
- are much easier to charge.
Wet acid batteries:
- need to be kept upright, must be charged in a ventilated place
- need to be topped up with fluid after charging.
- Airlines will carry all kinds of battery in the hold, but wet acid batteries need to be taken out of the wheelchair and put into a special sealed container.
Most wheelchair users will get the best results out of a high quality gel battery. AGM batteries are cheaper, but they do not last as many recharges. It is possible to buy pure lead plate batteries (usually the plates have added calcium to protect against corrosion), which give better performance. However, they are more expensive.
Get the most out of your batteries
Follow these simple steps to make sure your battery lasts a long time:
- Ensure batteries are fully charged before they’re fitted.
- After this, charge them every night, overnight.
- Avoid running them down until they’re almost empty – this will reduce their life span. If possible, they should be topped up during the day.
- Don’t over-charge – stop charging once the batteries are full, or use an intelligent charger which will do this for you.
- Only use a charger which is specifically designed for your battery type.
- If you want to keep the batteries topped up while you’re travelling, in-car chargers are available for some types of battery.
- They plug into the cigarette lighter socket and run off the car battery.
If you have good batteries, and you look after them, they should last for 400–500 cycles. However, they will wear out and need replacing during the life of the chair. Some wheelchairs have the batteries contained in sealed units. This may mean that you can only buy replacement batteries from the same manufacturer. These may
cost more, and they may not give you the performance you want. Ask about battery cost and performance before buying a powered wheelchair. Some people have reported being able to open the manufacturer’s sealed battery packs to fit their own replacement batteries.
Last updated: May 2015