24V wheelchair - Tap for 12V?

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SweetBearCub
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24V wheelchair - Tap for 12V?

Greetings.

I'm new here, so if this post is in the wrong part of the forum, please feel free to move it. I wasn't exactly sure of where to put it.

I use a power wheelchair for most of my mobility. Like a car, because I spend so much time in it, I want to make it more functional. I would like to figure out a way to tap its 2 12V batteries for 12V so that I can power the following items:

A) An automotive cigarette lighter/power port, to connect things like a USB charger for my cell phone. (Standard USB, 5V @ 500ma)
B) Future idea - A netbook. (30 watts?)
C) Future idea - LED lighting. (Forward illumination/rear markers)
D) A LOUD horn!

I am not very well versed in electrical theory, but from what I know, tapping only one of the batteries will result in it being drained faster than the other and will lead to killing the battery, stranding me without motive power, or possibly damaging the charger.

I would ideally like to have the system set up so that I can charge the batteries normally, by plugging in my standard 8A (Soneil) charger, and without having to add a third battery which I would have to charge separately. This would have the additional advantage of being able to monitor the charge level through the standard joystick display.

Fresh batteries will be installed on 4/15. I will take photos of the wiring setup and measure the available working space in the battery compartment, if needed.

Preferably, all the required electronics would fit in the battery compartment, to optimize space savings and protect them from weather.

How can I do all of this? About how much money would it cost, ballpark, assuming that I had someone do the work for me? (I can't get in a position to work on the chair comfortably)

Any comments/suggestions would be appreciated - Thanks!

Richard

marylandbob
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Re: 24V wheelchair - Tap for 12V?

What you need is a modified 16 to 32 volt input, with 15 volt output, 15 ampere, D.C. to D.C. converter. The modification would involve re-setting the 15 volt output to 13.8 volts D.C.. to emulate the voltage available in a running car.This will permit you to have a steady voltage, derived from both your batteries, that is similar to what a car has, and if space is available, it could even charge an added 12 volt battery for accessories from your existing batteries. Yes, a skilled person will be needed to properly interface this addition. Where are you?-Bob

Robert M. Curry

SweetBearCub
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Joined: Tuesday, April 13, 2010 - 23:13
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Re: 24V wheelchair - Tap for 12V?

Bob, thanks for your reply.

If I'm not mistaken, you're talking about a 24V to 12V converter. I can tell you that space in/on a power wheelchair is at a high premium - There isn't much to work with. Adding a third battery would not be possible. Assuming that the converter and plugs are compact, they *should* fit inside my battery box. I was thinking that the automotive power socket could come out through the front of my battery box, just under my seat, with a rubber rain shield connected to it, to plug it when I'm driving in bad weather. That would require a Dremel tool and some ingenuity.

I'm in San Francisco, CA.

As far as I know, charging a smartphone through USB power and running LED lights and a loud horn (all my chair has currently is a weak piezo beeper) shouldn't take too much away from my total available power. If the 2 12V batteries normally power me for about 15 miles, how much range would I be giving up? 1/2 mile, less?

Also, can you give me a ballpark estimate on how much these modifications might cost me?

Thanks!

reikiman
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Re: 24V wheelchair - Tap for 12V?

I didn't quite follow what Bob said about modification - but this kind of DC-DC is what I think would be needed: http://www.evparts.com/prod-DC2470.htm

24v in, 12v out, with enough amps capacity to do far more than you need. There may be smaller ones if you hunt around, just not via that vendor.

- David Herron, The Long Tail Pipe, davidherron.com, 7gen.com, What is Reiki
- Electrified Electra To

technowhiz
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Joined: Sunday, May 23, 2010 - 11:01
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Re: 24V wheelchair - Tap for 12V?

Most wheelchairs running 24 volt batteries are using two 12-volt batteries IN SERIES.

Tapping into one of them for a horn or phone will have an insignificant result. I used a 10-amp truckhorn on mine during the celebration after THE hockey game (there is only ONE real hockey game when we beat the US)and had no problems whatsoever. I still use it every day.

if you're really concerned about it buy a proper battery switch or other solution from a marine supply or RV dealer. Maybe Auto Marine Electric or RP Electric can help too.

The ignorance of wheelchair companies in Vancouver is infuriating... go to any RV or marine dealer where they know how to do this kind of work in their sleep.

technowhiz

Volts that jolts
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Re: 24V wheelchair - Tap for 12V?

Hello All,

I have been working in the health care industry for a while now as a technician and I've been wondering recently if there is a market for 12V outlet installations on Scooters and Power wheelchairs? I live in the greater Vancouver area.

I noticed this is an old post so I hope "SweetBearCub" was able to get done what he needed for his power wheelchair.

Lee

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