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Converting dc to ac

by Missouri Bob
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Missouri Bob
#1
Feb27-09, 01:59 PM
P: 3
i have a used electric chair for my mother for our stairs. we installed it and it seemed to work fine for a couple days. then the batteries began to lose charge. the chair is pwered by batteries that are charged by an ac plug in, but somehow the batteries are not getting charged. i would like to by-pass them and have the chair run on ac only. can i do that? the chair runs on two 12v batteries.
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Topher925
#2
Feb27-09, 02:15 PM
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Sure you can but your will need to a power cable or some way of supplying AC power to the chair as it moves up and down the stairs.
Missouri Bob
#3
Feb27-09, 02:28 PM
P: 3
the chair is already set up to do that. the batteries are in the chair and from there is a cable that runs to a charger, then into a plug in the wall. my question is how do i get it to run off of ac instead of the dc from the batteries?

Topher925
#4
Feb27-09, 02:57 PM
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Converting dc to ac

Interesting. I'm guessing the batteries are there in the first place because the chair requires a very high amp draw that some home's electrical wiring wont be able to handle. The first thing I would do is determine what type of amp draw the chair requires and then check to see if the electrical wiring in the house can dish it out. If the power requirement is to great, you may not be able to run it off of AC. This may require a professional electrician if you don't want to risk burning the house down.

I would also look at getting some better batteries as a plan B.
Pumblechook
#5
Feb27-09, 03:12 PM
P: 359
You need a mains power supply unit with the correct DC output. Ham Radio shops stock 12 V mains power units at 20 - 30 Amps for running radio equipment at home which can also be used in cars (12 v only available).
MATLABdude
#6
Feb27-09, 03:15 PM
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I don't think you can run a DC motor off of AC. Especially since AC would be 120 Vrms and the coils are wrapped for 24 V DC. I think you may have arcing and a fire in short order.

However, if it is designed for AC (there should be a plate on the motor that gives its operating specifications) or the coils have thick enough insulation, then your mom will have a much faster ride up and down the stairs!

However, your best bet is to contact the company that made this thing and tell them that the charger isn't working.
Pumblechook
#7
Feb27-09, 03:19 PM
P: 359
High voltages (electric shock) and high currents (arcing and burning) are dangerous.

If you are not sure what you are doing DONT.
Topher925
#8
Feb27-09, 04:13 PM
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Quote Quote by MATLABdude View Post
I don't think you can run a DC motor off of AC. Especially since AC would be 120 Vrms and the coils are wrapped for 24 V DC. I think you may have arcing and a fire in short order.
There is obviously a rectifier/converter already built into the chair since its charging 12v batteries. Although I doubt it would handle the current that the chair motor requires. Either way, simple motor controllers that go from AC to DC aren't that difficult to come by.
Naty1
#9
Feb27-09, 05:03 PM
P: 5,632
How do you know the batteries have lost charge??? Can you check the charge via a hydrometer or a voltmeter??
dlgoff
#10
Feb27-09, 05:28 PM
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Quote Quote by Naty1 View Post
How do you know the batteries have lost charge??? Can you check the charge via a hydrometer or a voltmeter??
Yes and/or maybe they are not being charged. Have you checked the wiring from the charger to batteries?

BTW Welcome to PF Missouri. Are you a basketball fan? Rock Chack Jayhawks.
Missouri Bob
#11
Feb28-09, 07:58 AM
P: 3
i have tried to contact the company several different times, and when i've actually talked to a person they will not help, they're out of europe. they have a rep about three hours from me who said his service call alone for that distance would be $300. the chair cost $500.

the batteries SOUNDED like they were going dead. we hoped the old batteries were just faulty and bought new ones. they worked fine for a couple days and then they started dying, like they were not being recharged.

i was an electrician apprentice for three years, but with this chair I don't really know what i'm doing. i'd like to be able to do without the batteries and somehow convert the ac power to work the dc motor.


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