12VDC Accessoies on power chair

[pvale]

I can't be the only person who wants to run 12VDC accessories on a power chair with 24V battery system. Well, I am an electrical engineer, and there is a wrong way and a right way.

The wrong way is to tap across the most negative battery. the extra load applied for 12 stuff will unbalance the charge on your batteries, and shorten the life of them considerably.

The right way is to get a 24V-12V DC-DC converter. They are available, just google DC-DC converter. The one I have that I am gathering materials to wire is;

Motormate DC-DC Power Converter. Input is 20-32VDC, and output is 13.8VDC @ 10A max. This unit is isolated completely from input to output, so I am not going to ground either side of the 13.8VDC. I didn't know if they ground the negative to the frame of the power chair or not, so I paid a little more for a totally isolated unit.

Output is regulated, and protected from overloads, and shorts. Now 10A is plenty for me to run such things as GPS, small 2meter ham radios, even up to a small spotlight I have.

I am going to fuse both 24V power leads at 7A. I'm going to use automotive ATC fuses and holders. I'm going to fuse the 13.8VDC output at 10A anyway. I'm going to run the output to a small project box from Radio Shack, with a toggle switch to switch on and off the converter, a pilot lamp so I know when it's on, a cigarrette lighter socket, and a couple of Anderson Powerpole sockets, since all of my ham radio equipment has been changed over to them.

Basically, if I am using the whole 10A at 13.8VDC, the converter will be pulling about 5.8A from the 24V batteries. Getting it to 10A will be rare for me, so I don't expect any detrimental effect to the batteries.

Now, while there are 24VDC to 110VAC inverters available, I do not recommend using them from the wheelchair batteries for 2 reasons;

1. While 12VDC presents little shock hazard to the user, not so for 110VAC.

2. Even a small 110VAC load through an inverter is going to pull significant amps at 24VDC. It will have a noticeable effect on your range on a battery charge.

On my Permobil C400 chair, there is no room "under the hood" to mount a box that is 6" x 5" x 4" tall. So, I'm going to be mounting it to the back of the seat. Only downside to this is; The converter I have has ventilation openings in it, and will not be waterproof.

So, there it is. When I actually get the materials together and do this project, I'll post pictures. Anybody with a modicum of electrical knowledge could do this. Just use wire loom tubing to cover all the wiring and zip-tie it to wherever the existing wiring is running.

Perry Vale

[peter57]

Good advise Perry.
Being an electrical tech. myself thats exactly the way i would do it.

The advise in not using the 24v to 110 volt inverters is important if you want to conserve battery life and not risk electric shocks.
It is even more "power hungry" in countries that have 240volts as their main power (like we do).

(you need to keep the battery power available for doing "drifts" in shopping malls dont you Glen )

cheers and good luck with the work Perry

[BarryG]

Thanks for the info Perry, I have always had fun playing around with anything electrical and electronic. Not a sparkie, but my dad was a ham radio operator (VE6RY) and a radio technician so I had a lot of electrical adventures including learning about capacitors when I was kid.

Where are going to mount the aerial for your ham rig?

[pamnandy]

This is how Andy ran his bipap. We hung it from his chair and used the "lighter plug." Worked great and made him very portable when he really needed to have that bipap away from home. We used carabeaner rings on the back of his chair and a Craftsman soft "toolbag" to hang it. I'm so glad you posted this!

[brooksea]

Cool! Printing this out!

[pvale]

Originally Posted by BarryG

Thanks for the info Perry, I have always had fun playing around with anything electrical and electronic. Not a sparkie, but my dad was a ham radio operator (VE6RY) and a radio technician so I had a lot of electrical adventures including learning about capacitors when I was kid.

Where are going to mount the aerial for your ham rig?

I'm going to use a long Handi-talkie antenna with a 19" counterpoise "tiger tail" hanging below it. Converter won't be able to supply full power operation of a 50W mobile rig, but should handle a Ht just fine.

73 de Perry N0MXJ

[boblandstar1]

Gimp gear sells plug n go converters and accessories. Link Wheelchair Charging Socket Battery Power Adapter

[pvale]

Oh, my God, thank you for that link, "pimp my ride" indeed. Lots of other things on there, massaging seat would be heavenly.

Thanks

Perry