Power carseat from 240v

[expleto]

I got two jag car seats that Ive set up as office chairs, they are pretty cool, and I dont get as sore sitting on them for 16 hours a day. I found the wiring diagram for the electrics, and tested it with a 15v 2 amp power supply. It kind of worked, enough for me to see that the bits all work. But I am not happy using that power supply as I think its over volted, and under amped.
It also made some of the wires get very hot.

I know it should be 12v, but not so sure how many amps it should be. I seen on a similar discusion on here, someone had sugested a 5amp charger.

http://jimbutterworth.co.uk/8seats.htm
thats where i got the wire diagram from, and the seats that i am using.

I know the volts have to be 12. but im not sure how amps work exactly, do you have to get exactly the right amount of amps, if so, how do i know how many... If its over amped, say 12v 10 amp, would that blow it up, or would it simply use the amps it needed. ???

Also what guage of wire should i be using so it wont melt.

Many thanks in advance.

 

[EFLImpudence]

Amps are not supplied; they are drawn by the load - the seats.

Are there any ratings in Watts on the motors?
If not, someone may know what is likely.
There will be more than one and they may be able to be on simultaneously.
Total Watts divided by 12 Volts = Amps.
Up to 14-ish Volts will be normal in a car.

You then need a supply which can cope with this current (amperage) or more.

 

[expleto]

Looked at the motors, but the just say 12v, no amps or watts. My current charger is 15v 4.5 amps. It works with that, but the wires are melting (getting very hot and making a burning smell), I think they are too thin, (they came from the power supply unit from an old pc).

Will it cause any problems using the 15 volt, or should I get a 12v.

Last thing I want is to have these go on fire, so want to make sure I get it right.

 

[KingboyD]

This circuit in a vehicle is normally fused at around 30A, there could be 3 motors per seat, I would expect each motor to draw between 4 - 7A under normal use. 2A is not going to be enough to move the seat with you sat on it

 

[EFLImpudence]

Looked at the motors, but the just say 12v, no amps or watts. My current charger is 15v 4.5 amps. It works with that, but the wires are melting (getting very hot and making a burning smell), I think they are too thin, (they came from the power supply unit from an old pc).

Looking on your link (I don't know if these are your seats) and it says there are two 20A motors (so 40A) in each seat so even if you only use one motor at a time you will need a minimum of 1.5mm² cable (just - larger would be better) and minimum 20A (25A would be better) supply so I would suspect that the charger is getting rather hot as well so would not last long.

Will it cause any problems using the 15 volt, or should I get a 12v.

15V would be alright but that will increase the current.


Have you thought about using a car battery?

 

[expleto]

I did think about using a car battery, but then, I would have to keep charging it all the time. when we start talking about 40 amp (isnt that like 480 volt ?), that sounds pretty mega for a charger, to be honest, I wish the seats were just manual. It might be better if I just get some more that are manual, probably cheaper, and a lot safer. The latter being the most important factor.

I see now why I could not find anything on the subject of using the electrics on car seats as office chairs. Pleanty of people making office chairs from carseats, but none using the electrics....

 

[skotl]

I did think about using a car battery, but then, I would have to keep charging it all the time. when we start talking about 40 amp (isnt that like 480 volt ?), that sounds pretty mega for a charger, to be honest, I wish the seats were just manual. It might be better if I just get some more that are manual, probably cheaper, and a lot safer. The latter being the most important factor.

I see now why I could not find anything on the subject of using the electrics on car seats as office chairs. Pleanty of people making office chairs from carseats, but none using the electrics....

Not 480 volts, but 480 watts, which is a measure of power (roughly volts * amps = power in watts).

You could look at something like this http://www.dabs.com/products/evga-750w-supernova-gold-psu-9BJM.html?src=2 which supplies 12V at 62A which, for short bursts as you'll need it, should do fine.
Note that if you're going to buy a computer power supply for this, you should buy one that is marked "80 Plus Gold" - don't buy a cheapie £15 from the shop on the corner.

You will also need thick automotive cable, rated at 60A (500W) or higher.

Edit: One other point - if you're using a PC power supply, you'll need to connect pins 16 and 18, or put a switch across both pins. See http://pinouts.ru/Power/atx_v2_pinout.shtml for more info.

 

[flameport]

Rather than using batteries or hashing together some solution with a PC power supply, just get one of these in a suitable rating:
http://www.tlc-direct.co.uk/Main_Index/Transformer_Index/Power_Supplies_Bench_Top/index.html

 

[expleto]

Rather than using batteries or hashing together some solution with a PC power supply, just get one of these in a suitable rating:
http://www.tlc-direct.co.uk/Main_Index/Transformer_Index/Power_Supplies_Bench_Top/index.html[/QUOTE]

By far the best option I think.

 

[ericmark]

From what has been said it will need to be quite a large power supply some thing like this one at 25 amp to take that load.

The volts will be around the 13.2 to 14.2 volt the unit shown would need to be in battery replacement mode not charging mode.

Even so there would be a problem using motor and heater. The heater likely does not need to be DC so possible a 12 volt lighting transformer could be used for the heating if required.

 

[bernardgreen]

Run the chair from a battery large enough to supply the 20 or 40 amps needed for the length of time the power is needed. Assuming it is moving or heating for only a few minutes in each hour then a 10 amp hour battery would be more adequate as regards capacity, The battery would need to be capable of supplying that amount of current ( maximum discharge rating > 40 amps )

The power supply could then be a constant trickle charger charging the battery at less than an amp.

 

[JohnD]

I think its over volted, and under amped.
It also made some of the wires get very hot....If its over amped, say 12v 10 amp, would that blow it up, or would it simply use the amps it needed. .

...about 40 amp (isnt that like 480 volt ?)

I think you do not understand the relationship between volts, amps, watts and heat.

In the car, the seat motors will work with the engine off or running, meaning that battery voltage can be between about 11v and about 15v. However the car battery might be 100Ah so has huge capacity.

They are rarely used for more than a few seconds at a time, and some models disable the rear seat motors temporarily if they are used excessively and repeatedly, e.g. by a child playing with the controls. Normal brief and intermittent usage enables heat to dissipate.

They are however designed and built in the expectation (some models) that the seat position will change every time the driver's key is inserted or removed, so the mechanism is quite durable.

I agree with Bernard that a small battery, I think SLA, would provide the brief and intermittent high currents you need, with a trickle charger to keep it topped up. A motorcycle battery would probably be suitable, intended to run a bike starter motor, and quite small.

Incidentally, if you want to use the seat heaters, it is worth knowing that the car monitors battery voltage, and curtails or shuts down supply to the heaters if voltage is dropping (e.g. stuck in traffic or parked) to prevent draining the battery.