ems@Apple.COM (Mike Smith) (08/18/89)
There has been a bit of discussion about electric cars and their future use. I would like to suggest that there is a clear and present market of 'electric cars' and they could benefit from improvements. A friend is in an electric wheelchair. It is, in all important respects, a miniature electric car. It has steering, batteries, electric motors, etc. It also has a rather old an crude level of technology. It has no built in charger. Why? If she is at school (she teaches) she must monitor her power usage. If it get's too low she is stuck. There is no small portable WEATHERPROOF battery charger that could be tucked under the chair for use in such a problematic situation. It cannot be recharged from her van. She has a fully custom driving station built into her van, yet it has no provision to charge the chair while in motion. On at least one occasion she 'ran out of juice' on the way to her van. A kind passer by wheeled her into her van so that she could drive home. Then she had to wait for someone to notice her in the van to wheel her into the house to the battery charger. This is barbaric. It uses plain old lead acid batteries. I would think that a safer and more effective battery could be identified ... At the very least lead-acid gel cells would be less prone to acid leakage. To get real exstream, there is a fixed (and rather small) range to the on-board battery. Why is their no 'power trailer' that could be pulled behind the chair with either more batteries or even a small generator? (Come-on you 'hybrid electric' folks, surely you can come up with a small, QUIET generator or fuel cell). Yes, I'm frustrated to watch a friend deal with limitations of technology that seem to me to be bogus. There are so many known technologies that could be used to make the electric wheelchair more functional. It is an excellent place for the electric car folks to prove their concepts. After all, the customer is already sold on electric vehicles and would love to have ANY improvements! So tell me, why are electric wheelchairs at the trailing rather than the leading edge of electric vehicle technology? -- E. Michael Smith ems@apple.COM 'If you can dream it, you can do it' Walt Disney This is the obligatory disclaimer of everything. (Including but not limited to: typos, spelling, diction, logic, and nuclear war) -- E. Michael Smith ems@apple.COM 'If you can dream it, you can do it' Walt Disney This is the obligatory disclaimer of everything. (Including but not limited to: typos, spelling, diction, logic, and nuclear war)
spf@cbnewsl.ATT.COM (Steve Frysinger of Blue Feather Farm) (08/18/89)
From article <3659@internal.Apple.COM>, by ems@Apple.COM (Mike Smith): > A friend is in an electric wheelchair. It is, in all > important respects, a miniature electric car. It has > steering, batteries, electric motors, etc. It also has > a rather old an crude level of technology. > It has no built in charger. Sears carries fairly lightweight 12-volt chargers. Space may be a problem, but she could probably find one less than 10x6x6". If nothing else, she might want to keep one at school. > It cannot be recharged from her van. Of course it can! All she needs is a connector (probably dashboard mounted). The alternator and voltage regulator of the van will do the rest. This is the same principle as jumper cables. Hooking a dead car's battery to a live car's battery allows the live one's battery (and alternator) to charge the dead one. You could probably rig up a connector to do this for your friend, and it sounds like it would be much appreciated. > It uses plain old lead acid batteries. In the above I've assumed that these are 12-volt. If they are 6-volt she should either by a 1940s van (just kidding) or she'll need a convertor in her dashboard connection. Still no big deal. > To get real exstream, there is a fixed (and rather small) range > to the on-board battery. Why is their no 'power trailer' that > could be pulled behind the chair with either more batteries. It sounds like this is something you could easily build yourself. > So tell me, why are electric wheelchairs at the trailing > rather than the leading edge of electric vehicle technology? > 'If you can dream it, you can do it' Walt Disney I am not disagreeing with you - such techologies should certainly be a part of the wheelchair product. But with your friend's interest at heart, and your Disney quote in mind, I offer these suggestions so that you can help her situation improve. Steve Frysinger
raoul@eplunix.UUCP (Otero) (08/19/89)
Hmmm. Not that difficult, actually, I'm surprised it hasn't been done. To recharge off a car system might be awkward unless you upgrade the alternator, but a couple of hefty voltage regulators to limit current flow to 10% of the Amp-hour rating of the battery should do quite nicely off a car voltage, plus a few parallel diodes to make sure no reverse flow happens if the voltage is higher than the car. And a fuse just in case something blows.... Take a look at the National Semiconductor LM117 for something that can dissipate 20 watts easily, and only costs a few dollars. There is even a good design for a constant-voltage, constant current recharger included in the manual. This is what you really want for lead acids. Let me know if I should post it. Off of 120 Volt house current, I would suggest a separate AC/DC converter and use the same voltage regulator. Power One makes good ones, but anyone should be able to whip you up *something* if you don't care too much about precision outputs. I suspect the major problem would be water-proofing and idiot-proofing it. (What if I stuck my tongue in the socket and lightning hits the cord? That sort of thing....) I just put a recharge circuit into some medical equipment, and the safety standards are astonishing. The only way someone can get fried with these standards is if they douse it in gasoline, shove their head in, and light a match inside. If your friend would like, I can send circuit diagrams. It's about an afternoon's work to do, and would probably cost $50-$100 with case. Call it 6" cubed. Would that be reasonable? -- Nico Garcia Engineer, CIRL Mass. Eye and Ear Infirmary eplunix!cirl!raoul@eddie.mit.edu
edm@nwnexus.WA.COM (Ed Morin) (08/19/89)
ems@Apple.COM (Mike Smith) writes: >So tell me, why are electric wheelchairs at the trailing >rather than the leading edge of electric vehicle technology? As depressing as it seems, I suspect this is so because the application of technology is in direct proportion to overall demand and potential profit rather than sympathy. The same is true for wonder drugs that only a few people need - mass producing them is not profitable because not enough people need them. (i.e. not enough people are physically crippled) -- Ed Morin Northwest Nexus Inc. "Unix Public Access for the Masses!" edm@nwnexus.WA.COM
hollombe@ttidca.TTI.COM (The Polymath) (08/19/89)
In article <3659@internal.Apple.COM> ems@Apple.COM (Mike Smith) writes: }A friend is in an electric wheelchair. ... }It has no built in charger. Why? If she is at school (she }teaches) she must monitor her power usage. If it get's too }low she is stuck. ... CSU, Northridge, at least, has addressed the problem. They have a room on campus dedicated to recharging wheelchairs. The electricity's free and, I think, they have chargers available. What keeps your friend from buying a trickle charger and carrying it with her? They're small, light weight and inexpensive. Available at most auto parts stores. -- The Polymath (aka: Jerry Hollombe, hollombe@ttidca.tti.com) Illegitimati Nil Citicorp(+)TTI Carborundum 3100 Ocean Park Blvd. (213) 452-9191, x2483 Santa Monica, CA 90405 {csun|philabs|psivax}!ttidca!hollombe
wbrown@beva.bev.lbl.gov (Bill Brown) (08/19/89)
In article <1526@cbnewsl.ATT.COM> spf@cbnewsl.ATT.COM (Steve Frysinger of Blue Feather Farm) writes: >From article <3659@internal.Apple.COM>, by ems@Apple.COM (Mike Smith): >> A friend is in an electric wheelchair. It is, in all >> ... >> It cannot be recharged from her van. > >Of course it can! All she needs is a connector (probably dashboard >mounted). The alternator and voltage regulator of the van will do >the rest. This is the same principle as jumper cables. Hooking a >dead car's battery to a live car's battery allows the live one's >battery (and alternator) to charge the dead one. You could probably >rig up a connector to do this for your friend, and it sounds like >it would be much appreciated. > It probably shouldn't be hooked up direct: maybe one of the "splitter" boxes used on RV setups would be the way to go. These gizzies are esentialy a couple of diodes which allow both batteries to be charged by the alternator without having the relatively well charged (starting) battery dump mucho current into the relatively discharged (lighting, etc) battery, on in this case the wheel-chair battery. No real "science" here - just looks like an application for existing stuff just waiting to happen. (all this assuming a 12-volt system on the wheelchair) -bill wlbrown@lbl.gov Disclaimer: These opinions are my own and have nothing to do with the official policy or management of L.B.L, who probably couldn't care less about employees who play with trains.
edm@nwnexus.WA.COM (Ed Morin) (08/19/89)
spf@cbnewsl.ATT.COM (Steve Frysinger of Blue Feather Farm) writes: >Sears carries fairly lightweight 12-volt chargers. Space may be ^^^^^^^ I don't know too much about wheel chairs, but electric cars are certainly not 12-volt systems. If her system were even 24-volts (2 car batteries in series maybe) this whole idea goes out the window and replaced with a lot of complication. Well, a DC-to-DC converter at the least so she could get a jump start... :-) -- Ed Morin Northwest Nexus Inc. "Unix Public Access for the Masses!" edm@nwnexus.WA.COM
ems@Apple.COM (Mike Smith) (08/19/89)
In article <3637@helios.ee.lbl.gov> wbrown@beva.bev.lbl.gov (Bill Brown) writes: >In article <1526@cbnewsl.ATT.COM> spf@cbnewsl.ATT.COM (Steve Frysinger of Blue Feather Farm) writes: >>From article <3659@internal.Apple.COM>, by ems@Apple.COM (Mike Smith): >>> A friend is in an electric wheelchair. It is, in all >>> ... >>> It cannot be recharged from her van. >> >>Of course it can! All she needs is a connector (probably dashboard >>mounted). The alternator and voltage regulator of the van will do >>the rest. This is the same principle as jumper cables. Hooking a >>dead car's battery to a live car's battery allows the live one's >>battery (and alternator) to charge the dead one. You could probably >>rig up a connector to do this for your friend, and it sounds like >>it would be much appreciated. >> > >It probably shouldn't be hooked up direct: maybe one of the "splitter" >boxes used on RV setups would be the way to go. These gizzies are >esentialy a couple of diodes which allow both batteries to be charged >by the alternator without having the relatively well charged (starting) >battery dump mucho current into the relatively discharged (lighting, etc) >battery, on in this case the wheel-chair battery. > >No real "science" here - just looks like an application for existing >stuff just waiting to happen. > >(all this assuming a 12-volt system on the wheelchair) Ahh, and therin lies the rub ... Chairs have funny connectors from the batteries to the control harness. They are decidedly NOT designed to be plugged and unplugged by a person with limited arm mobility (just the kind of person who needs an electric wheelchair). They do funny things to connect the two 12 volt batteries into one 24 volt source. The person in question cannot REACH the dash. There is a custom control/steering panel that moves to her lap when the chair locks down. She cannot put force into a plug (push or pull) but can push buttons and move a joystick. The usual behaviour is to have one's 'attendant' unplug the batteries and hook up the charger ... The desired behaviour is to roll into the existing custom chair lockdown and have it automatically hook up a charging circuit. It also isn't just a matter of getting a Sears Best charger and slinging it under the chair ... The chair often gets WET in the rain. Would YOU want to sit on top of a wet metal chair with the typical wide open charger box (vent slits) dripping onto the batteries ? So one needs a Very Smart charger to figure out what voltage it is being fed (12v, or 110, or?) and turn it into what is needed (12 v x 2 batteries or 24 v and charge them in series?). It should also be small, light weight, relatively flat, not get very HOT in operation (efficient), and MUST be WEATHERPROOF. It also would need to be able to automatically cut out the control feed during charging ( since controls must be 24 v, not the 12v from 2 parallel batteries ) and it should default to returning control and stopping charging if anything looks funny (i.e. if it thinks it or something else is broken it should get out of the way and return control to the operator, like in a power outage from the charging supply). Oh yes, and it must not overcharge the batteries at all. It isn't quite as easy as it looks at first glance... My hardware skills aren't quite good enough to design such a device, but I would be willing to finance construction ... and my wheelchair using friend has volunteered to try out the product. Mike -- E. Michael Smith ems@apple.COM 'If you can dream it, you can do it' Walt Disney This is the obligatory disclaimer of everything. (Including but not limited to: typos, spelling, diction, logic, and nuclear war)
ems@Apple.COM (Mike Smith) (08/19/89)
In article <5481@ttidca.TTI.COM> hollombe@ttidcb.tti.com (The Polymath) writes: >In article <3659@internal.Apple.COM> ems@Apple.COM (Mike Smith) writes: >}A friend is in an electric wheelchair. ... > >}It has no built in charger. Why? If she is at school (she >}teaches) she must monitor her power usage. If it get's too >}low she is stuck. ... > >What keeps your friend from buying a trickle charger and carrying it with >her? They're small, light weight and inexpensive. Available at most auto >parts stores. Chairs do not use the standard means of charging. Their is a 'funny connector' that the charger plugs into. Lets a single 12v charger charge 2 12v batteries that are used in series as a 24v source to the chair. The alternative is to unbolt the battery covers and undo the cables at the batteries. UCK. It would be possible to put the funny connector onto a 'small' charger, but remember that the chair is not mobile while the charger is connected and that the person in the chair is there because she has very limited use of her arms. i.e. no significant force or movement at odd angles. So you need something that the average 'good Sam' passing by can't screw up or be confused by (which isn't the standard connector on the chair ...). What you need is a regular wall outlet plug on a 12ft or so cable that is hooked into a permanently affixed object on the chair that automatically does all the 'plugging' when it senses 110 VAC on it's input cable. -- E. Michael Smith ems@apple.COM 'If you can dream it, you can do it' Walt Disney This is the obligatory disclaimer of everything. (Including but not limited to: typos, spelling, diction, logic, and nuclear war)
miker@orca.WV.TEK.COM (Mike Reiney) (08/19/89)
I really enjoy reading these articles. With all the conservationist discussions going on in this newsgroup, why is it necessary to repost the original article and followups in every followup article? Ditto for all the cute signature lines and disclaimers. Wonder how much energy is required to post and for everyone to read one extra word?
deanr@sco.COM (Dean Reece) (08/21/89)
In article <169@nwnexus.WA.COM> edm@nwnexus.WA.COM (Ed Morin) writes: >spf@cbnewsl.ATT.COM (Steve Frysinger of Blue Feather Farm) writes: > >>Sears carries fairly lightweight 12-volt chargers. Space may be > ^^^^^^^ > >I don't know too much about wheel chairs, but electric cars are certainly >not 12-volt systems. If her system were even 24-volts (2 car batteries >in series maybe) this whole idea goes out the window and replaced with a >lot of complication. Well, a DC-to-DC converter at the least so she could >get a jump start... :-) Why? If it IS two car batteries, then just charge them one at a time. If you wanted to get fancy, you could rig a large 4 pin connector that had both terminals of both batteries. When plugged into the wheel chair, they are wired in series. When plugged into the dash charger, they would be wired as two independent batteries, each being independently charged by individual chargers from one alternator. If it is a single 24 volt battery, that would be a problem, but I believe you can get custom wound alternators for such things (I even seem to remember reading about a fan belt driven, 117 volt generator available as an option on some VERY old Ford Thunder-Chickens :-) just my 2 cents worth - standard disclaimer -- Dean Reece (deanr@sco.COM) The Santa Cruz Operation, Santa Cruz, CA 95010
ems@Apple.COM (Mike Smith) (08/22/89)
In article <169@nwnexus.WA.COM> edm@nwnexus.WA.COM (Ed Morin) writes: >spf@cbnewsl.ATT.COM (Steve Frysinger of Blue Feather Farm) writes: >>Sears carries fairly lightweight 12-volt chargers. Space may be ^^^^^^^ >I don't know too much about wheel chairs, but electric cars are certainly >not 12-volt systems. If her system were even 24-volts (2 car batteries The system is, indeed, 24 VDC. Two twelve volt deep cycle leadacid batteries in series. There is a 'funny plug' that connects them to the control harness in series. It also connects them to the home charger in parallel, but not at the same time ... >in series maybe) this whole idea goes out the window and replaced with a >lot of complication. Well, a DC-to-DC converter at the least so she could >get a jump start... :-) The 'dream charger' would be a DC to DC converter (with an AC -> DC rectifier front end for household use) that used switching circuitry to reduce heat generation and reduce transformer size to the small side. The whole thing sealed in a waterproof metal enclosure with weatherproof cables. Then it could run from [{any Hz.}110vac,220vac,12vdc,24vdc,etc. ...) -- E. Michael Smith ems@apple.COM 'If you can dream it, you can do it' Walt Disney This is the obligatory disclaimer of everything. (Including but not limited to: typos, spelling, diction, logic, and nuclear war)
cook@stout.ucar.edu (Forrest Cook) (08/22/89)
In article <1526@cbnewsl.ATT.COM> spf@cbnewsl.ATT.COM (Steve Frysinger of Blue Feather Farm) writes: >From article <3659@internal.Apple.COM>, by ems@Apple.COM (Mike Smith): >> A friend is in an electric wheelchair. It is, in all ... >> It cannot be recharged from her van. >Of course it can! All she needs is a connector (probably dashboard >mounted). The alternator and voltage regulator of the van will do the rest. I have a friend who is wheelchair bound and has some similar problems. His chair uses 2 12V deep cycle marine batteries in series for a 24Volt supply. He also has a customized van with no charger. There are several ways that the batteries could be charged from the van: 1: The inefficient, easy way - use an inverter to convert the 12V from the van up to 110 VAC and run the normal charger off of that. 2: The slightly less inefficient way - Make a custom inverter/dc supply that can generate around 28 V from 12 V and charge the batteries with that. 3: The tricky but efficient way: - Build some switching arrangement on the two 12V batteries so that they can both be charged in parallel directly from the alternator. Some kind of current limiting/schottky diode scheme would probably be necessary to prevent killing the alternator or having a charged battery dump too much juice into a dead battery. Personally, I would try #2 first because it requires the least modification to the chair. My friend's wheelchair uses a very inefficient switching method to give him speed adjustment. The current is either run directly to the motor (fast) or run through a giant nichrome resistor (slow). I am currently checking out some IRFZ40-ND Hexfets to see if they can hold up in a pulse-width modulated switching circuit so that he can have continuously adjustable speed. ^ ^ Forrest Cook - Beware of programmers who carry screwdrivers - LB /|\ /|\ cook@stout.ucar.edu (The preceeding was all my OPINION) /|\ /|\ {husc6|rutgers|ames|gatech}!ncar!stout!cook /|\ /|\ {uunet|ucbvax|allegra|cbosgd}!nbires!ncar!stout!cook
wordy@cup.portal.com (Steven K Roberts) (08/22/89)
I can't help but wonder why nobody ever mentions solar power in discussions like this. The Solarex SX-LITE panels weigh about 2 pounds and put out 18 watts, at a retail cost of $175 or so. Admittedly this is not cheap, but that's 1.2 amps per panel of charge current (they're scaled for direct connection to 12V batteries, and can be series-connected for 24). Application is trivial... sunlight in, two wires out. Add a schottky to prevent dark discharge and you're done, unless the panels are substantially more robust than the batteries, in which case a controller is required. Solarex is at 800-521-SOLA and a Bay Area distributor is Energy Depot at 415-499-1333 in San Rafael. Cheers... Steven K. Roberts Nomadic Research Labs
raoul@eplunix.UUCP (Otero) (08/22/89)
In article <21503@cup.portal.com>, wordy@cup.portal.com (Steven K Roberts) writes: > I can't help but wonder why nobody ever mentions solar power in > discussions like this. Sudden images of Cutter John and the crew of the Star Chair Enterprise, wheeling actoss Bloom County at Warp 87.... In real life, though, wheel chairs are unwieldy enough without solar panel umbrellas. The point of the problem is to make things easier to handle and portable, not make it larger and more unwieldy. I liked the one gentleman's idea about different connectors for use and recharging, linking them in parallel persus series. But didn't the original poster mention that the user had little upper body strength or mobility? It's kind o' awkward to pull apart good sealed connectors. So, why not put in a DPDT relay at the recharge circuit that switches the poles of one of the batteries? The relay only goes on if there is 12 V recharge voltage. And maybe another relay at a 110 volt source, to connect that converter/recharger instead. And there is a very good reason not to recharge one battery at a time: A deeply discharged lead-acid in series with a fully charged one can have a reverse charge put on it by the charged one. This is very bad for lead-acids.... Manufacturers *laugh* at warranties if you try this. -- Nico Garcia Engineer, CIRL Mass. Eye and Ear Infirmary eplunix!cirl!raoul@eddie.mit.edu
georgep@vice.ICO.TEK.COM (George Pell) (08/23/89)
+In an article the original poster writes about recharging 24V systems: +The system is, indeed, 24 VDC. Two twelve volt deep cycle leadacid +batteries in series. There is a 'funny plug' that connects them to +the control harness in series. It also connects them to the home +charger in parallel, but not at the same time ... + 24V chargers are available for aircraft. They are somewhat more expensive than automobile chargers just because they say 'airplane'. You might also look for a golf cart charger. geo
john@stiatl.UUCP (John DeArmond) (08/23/89)
In article <21503@cup.portal.com> wordy@cup.portal.com (Steven K Roberts) writes: >I can't help but wonder why nobody ever mentions solar power in >discussions like this. The Solarex SX-LITE panels weigh about 2 >pounds and put out 18 watts, at a retail cost of $175 or so. Admittedly >this is not cheap, but that's 1.2 amps per panel of charge >current (they're scaled for direct connection to 12V batteries, For the same reason nobody mentions a squirrel in a cage or a crank generator or dry cells. None of these have within an order of magnitude of the needed current to charge these batteries. Hmm, letssee... typical deep discharge 12 volt battery is 100 amp-hours. At 1.8 amps charging, one would need about 55 hours of sunlight a day (assuming 100% effeciency) to recharge the thing. Funny, I misplaced my collection of 72 hour days. All I have now are 24 hour one. Won't work. -- John De Armond, WD4OQC | Manual? ... What manual ?!? Sales Technologies, Inc. Atlanta, GA | This is Unix, My son, You ...!gatech!stiatl!john **I am the NRA** | just GOTTA Know!!!
phil@diablo.amd.com (Phil Ngai) (08/23/89)
In article <3736@internal.Apple.COM> ems@Apple.COM (Mike Smith) writes: |The system is, indeed, 24 VDC. Two twelve volt deep cycle leadacid |batteries in series. There is a 'funny plug' that connects them to |the control harness in series. It also connects them to the home |charger in parallel, but not at the same time ... | |The 'dream charger' would be a DC to DC converter (with an AC -> DC |rectifier front end for household use) that used switching circuitry |to reduce heat generation and reduce transformer size to the small side. |The whole thing sealed in a waterproof metal enclosure with weatherproof |cables. Then it could run from [{any Hz.}110vac,220vac,12vdc,24vdc,etc. ...) Why make it so complicated? Seems like a straightforward application of relays to switch the batteries from the operating 24 volt series mode to a charging 12 volt parallel mode combined with a cheap trickle charger from an auto parts store would do the trick. (excepting the 220 thing.) -- Phil Ngai, phil@diablo.amd.com {uunet,decwrl,ucbvax}!amdcad!phil "Today surgeons are highly respected but they were once just grave robbers."
wordy@cup.portal.com (Steven K Roberts) (08/28/89)
John DeArmond pointed out, quite correctly, that my solar panel suggestion is of the wrong scale for powering a wheelchair. I probably should have clarified -- using solar would be pointless without a "real" charger as well.... but it is a not-insignificant trickle that could significantly extend range when outdoors. On my bicycle, I have a 72-watt array plus two isolated 10-watt panels --- almost 8 amps worth of 12 volts (actually about 7 of a higher voltage for charging). The cost/performance ratio is dubious and it takes up a lot of space for a wheelchair, but still... I'll wager there's someone out there who could take advantage of this approach (coupled, of course, with a line cord and traditional charger). Cheers... Steven K. Roberts, Nomadic Research Labs