Make:

Your going to need at least a 100W pannel to amake a difference in the longevity of the wheelchair's drive time. it would be really interesting to construct a pop-top convertible like roof, where the large flat solar cell could retract down to the back area (for entering a store), and pop back up to an overhead position for outside use. the added bonus, is it also functions as a rain shield in case your caught in a storm.

Reply to this comment

What kind of wheelchair is it? brand/model?

Reply to this comment

Have you seen this one?:
http://www.makezine.com/blog/archive/2006/09/solar_powered_wheelchair.html

Reply to this comment

NimH batteries have almost twice the energy density of lead acid batteries, and can be left in a discharged state for a long time without permanent damage. If the goal is simply to extend the range, the solution is simple: replace the current 24 volt lead acid with about 40 D size NimH batteries. This will give roughly a 20 amp draw capability, with twice the range. A new charger will be needed. www.batteryspace.com would have everything Norman needs, but there are plenty of other vendors.

I recently converted an electric bicycle from Sealed Lead Acid to NimH, and the range increased tremendously.

For max range, Lithium Polymer or Lithium Ion would be even better, but they tend to be more...flamable and trickier to set up.

Tho X. Bui
blahx3@thoxbui.com

Reply to this comment

I don't know much about powered wheelchairs, so my suggestion may seem very obvious: reduce the weight of the chair as much as possible. You'll get a little more range prior to your solar upgrade, and once the upgrade is complete, you'll be getting the most out of your solar power source. In addition to, or perhaps instead of a solar panel, you could have a crank connected to a generator. This way, if your batteries died at an inopportune moment, all you would need is to be wound up, like that character in Return to Oz. For the record, that last suggestion is very much in jest.

Reply to this comment

Does this help too?
I remembered this featured on the MAKE Blog:
http://www.treehugger.com/files/2005/04/don_dunkees_diy.php

Reply to this comment

Adding a small portable gasoline generator will probably be more efficient (and environmentally friendly) than a solar panel if you're just using it for the occasional jaunt into town. Probably cheaper too.

Reply to this comment

Actually, forget the generator. Make a small trailer to fit behind the wheelchair to carry some large deep cycle batteries. You'll probably even get some cargo room for groceries and what not on top. Run the batteries in parallel or have a relay/contactor switch between the pack in your chair and in the trailer. Charge the trailer when at home and you should be good to go.

Reply to this comment

I'm working on re-engineering my power chair into something that's more efficient and environmentally friendly. I need the "Cadillac" of power chairs given my SCI, full tilt, recline, leg and seat elevate. The average decked out power chair weighs in at about 300 pounds with 100 of that being the batteries. It's going to take me some time to get this all together, but it is possible. Currently, chair design and construction is driven by insurance payments. Just a little research and I've found technologies that will significantly reduce the weight, yet increase the function. My initial goal is to create after market replacement parts that cost the same or less than to replacement cost of the parts that wear out constantly, but only have a very short warranty. I'll be posting my solutions all over the net on the major mobility sites like wheelchair junkie. I'm at least 6 months from the first round, since I need to make a trailer to transport my chair in an unmodified vehicle and one I can pull behind my chair. Keep a look out and you only will need a 100 watt PV system if you want to use the 120 v charger. You can go straight from the PV, to a 12v charger to your chair's batteries. I'll post the data as soon as I finish a prototype.

Reply to this comment