Built-in & Removable Prosthetic Batteries
- Built in and Removable Battery styles
- Ideal for Prosthetic Terminal Devices and Wrists
- Lithium-ion & Lithium-polymer chemistries
- Variety of shapes, sizes and weights
- Capacities from 250 to 2000 mAHr
- Compatible with all manufacturers’ components
- 7.4 volt (nominal)
Choosing the Right Battery:
There is a lot of confusion about new battery technology. The discussion below should help you determine which battery style and capacity is best for your prosthetic application. The new battery chemistries have greater energy density, so they provide more capacity, higher cell voltage, smaller size and are lighter in weight. They have other beneficial features, like no “memory” problem common with the old Ni-Cad batteries and they can be recharged quickly and topped-off at any time. Finally, they are more environmentally friendly.
Battery Styles – Removable & Built-in:
Removable and Built-in prosthetic batteries are available from LTI in two chemistries: Lithium-ion and Lithium-polymer. Each battery style has its advantages and disadvantages which is why we offer both. In general, removable batteries are used when it is not possible to get adequate capacity from a single built-in battery to provide adequate power to run the prosthesis all day. Since built-in batteries are offered with capacities ranging from 200 mAHr to 2000 mAHr, it is rare that a built-in battery could not be used. However, a 2000 mAHr battery is quite large (70 mm long) and relatively heavy (103 grams), and this may be too large or heavy for a particular prosthesis. In these cases, a removable battery is a good choice. The user can keep one battery in the prosthesis and carry a charged replacement battery, thus keeping the weight down.
Built-in batteries can more easily be concealed in the prosthesis for better cosmesis. The battery can be placed in a cavity in the socket or between the inner and outer-sockets, so the only thing showing is the Battery Recharge Module (recharge connector and on/off switch).
In cases where cosmesis is a high priority or less capacity is required, one of the built-in batteries may be the best choice. They are offered in different capacities and sizes so that the clinician can choose the best size for the application. Since battery weight and size for a given chemistry is directly related to capacity, one should choose the minimum battery capacity required to do the job. Generally, the goal is to provide a built-in battery that enables the user to operate their prosthetic system for a full day without recharging. Since these batteries are offered in a variety of capacities, it is not difficult to choose one that suits the application. Often, 750 mAHr built-in batteries are used for adult trans-radial prostheses with traditional terminal devices and these usually work well for moderate to heavy-duty users. For lighter-duty adult users, a 450 mAHr battery may be suitable. For children, typically the 450 mAHr battery is used. Some light-duty users (children) may find that the 250 mAHr battery is suitable.
The new multi-articulating hands (bebionic & iLimb Pulse) have more motors than traditional terminal devices and therefore tend to consume more power. As a result, these batteries often need larger capacity batteries to enable the user to operate them all day. Typically these hands require between 1300-2000 mAHr capacity batteries. They also require batteries that can provide greater current to operate the multiple motors simultaneously.
Battery Recharge Modules:
A Battery Recharge Module is supplied with each built-in battery and are available in two styles; 1) with connectors and, 2) with cables. The Modules with on-board connectors are more compact, but tend to be higher profile. The Modules with cables are a lower profile but have cables that must be accommodated within the prosthesis. Recharge Modules provide an on/off switch and a recharge port for the charger. They are sized for the battery and charger.
Sample Recharge Modules
Most upper-limb prosthetic devices (terminal devices & wrists) are designed to operate on 7.2volts (nominal) with the exception of powered elbows. Some can tolerate slightly higher voltages, but caution should be used here to avoid damage to products and loss of the manufacturer’s warranty.
Powered elbows often have higher voltage batteries to operate the more powerful motor required to flex the elbow under load. The LTI Boston Digital Arm has an 11 volt (nominal) battery for the elbow motor, but this prosthetic system also has an on-board voltage regulator to reduce the voltage for the terminal device to 7.4 volts. This enables the Boston Arm to be compatible with all terminal devices, including the new multi-articulating hands (bebionic & iLimb Ultra).