Warning!!!
This page describes how I added a power port to a wheelchair to run external devices off of the wheelchair's battery. I don't personally endorse others doing this, for the following reasons: this most likely will void the wheelchair's warranty; it could damage the wheelchair; the wheelchair batteries are large and potentially dangerous if they short; this modification requires some skill with wiring and electronics; the description worked for a Permobil C300 but may not necessarily work for another brand or model of wheelchair; etc.
I will describe how I made the modifications. I take no responsibility if others attempt the same or similar steps. Please do not contact me if you have questions or encounter problems. Please make sure you have ready access (preferably in the same room with you) to someone skilled and knowledgeable in electronics and wiring before you attempt any modifications.
I will describe how I made the modifications. I take no responsibility if others attempt the same or similar steps. Please do not contact me if you have questions or encounter problems. Please make sure you have ready access (preferably in the same room with you) to someone skilled and knowledgeable in electronics and wiring before you attempt any modifications.
Here We Go
The Permobil C300 has two 12 volt batteries (generally, sealed gel batteries) that are wired in series. This means the wheelchair is running on 24 volts. Lots of devices, such as BiPAPs, CPAPs, cell phones, laptops, have power adapters that can plug into car cigarette lighter sockets, which means that they require 12 volts. In order to tap into the wheelchair batteries to get 12 volts, you could wire a socket to a single battery. The downside to this is that the two batteries will drain unevenly. Alternatively, you could wire the series endpoints to a 24v-to-12v converter. This is the approach I took.
I used the following components:
The 24v-to-12v converter I used was an Alfatronix PV6s. This specific converter was listed in a schematic from another person who did the same type of modification to their wheelchair. I used this schematic and simplified some things for my modification. I found the Alfatronix on ebay. I am not familiar enough with these types of components to know if there are suitable alternatives more easily available. This particular unit has worked well in two modifications I did.
I could not find a picture of the exact adapter I used, but almost any will do. Basically, you want to get something that plugs into the cigarette lighter socket in a car and gives you one or more sockets at the other end. Having more than one socket is definitely useful for powering more than one device. Usb connectors are useful for charging cell phones.
I cut off the plug and attached the wires to the 12v output of the Alfatronix. Before doing this, I made sure I had the polarity of the wires correct by first plugging the adapter into a car and measuring the voltage across the tip and the side contacts to determine which is ground and which is +12v. Then, I used the continuity checker of the voltmeter to verify which wire led to tip and which to the side and labeled them.
I cut off the plug and attached the wires to the 12v output of the Alfatronix. Before doing this, I made sure I had the polarity of the wires correct by first plugging the adapter into a car and measuring the voltage across the tip and the side contacts to determine which is ground and which is +12v. Then, I used the continuity checker of the voltmeter to verify which wire led to tip and which to the side and labeled them.