[Kong]

Hello

i need some help on a particular subject which im not familiar with and dont really know where to start.

The setup described below is not for a car but for a moving vehicle.

i need to power a 19inch lcd screen( an actual screen or a laptop), but not from the mains. it has to be portable so that means, it would have to work with maybe a rechargable battery pack, and then be charged when the battery runs out. i need as much running time as possible. if approximately 10 hours is possible off one charge then that would be perfect.

does anybody know if this is possible and if so can they provide me with some information or any links to products that i could purchase.

if it will not work then could you suggest a set up? maybe using solar panels or using a dynamo to power the lcd screen.


if you could provide me with details specifications such as lcd power consumption, battery pack run time etc... that would be most helpful

thank you for your help.

[clockworks]

If you have access to the vehicle's battery, the easiest option would be an inverter. You can buy these to plug into a cigarette lighter socket, either 12v or 24v. They convert the DC from the battery to AC mains, so you just plug the device in as normal.

If you can't take power from the vehicle battery, you'll have a problem getting anything portable to run for 10 hours without recharging. A 19" screen takes about 50 watts, that's 4 and a bit amps at 12v. Allow for inefficiency in the invertor, that's 6 amps. Times 10 hours = 60Ah. That's the capacity of a large car battery, rather heavy to carry around.

[Kong]

what about an uninterruptible power supply unit?

if i used UPSs, do you know if it would be possible to charge a line of trolleys, each with a ups, while they are nested at their bay? so if they all connected to each other and ultimately one connected to the mains, could they all charge? or would each one hav 2 b connected to a mains to charge?

do you know how much power a laptop requires compared to a lcd screen?

i think that a laptop would be a better option as it would need to have wireless to receive advertisements. that way all the trolleys could receive the adverts. also i would want a pda connected to the trolley for gps and other little user needs.

any help is much appreciated, and thanks for the help so far, it has been very helpful.

[clockworks]

Are you trying to fit the screens to supermarket shopping trolleys? Is it a real project, or a theoretical one?

My laptop PSU is rated at 60 watts (16v @ 3.75A), but it's a small, ultraportable, laptop.

Using a UPS would have the same limitations as using batteries, since a UPS is just a battery, charger, and inverter in one box. Still a lot of dead weight to push around. There's no reason why it wouldn't work, though keeping the things charged would be the problem.
"Nesting" would be a problem, as UPS in the trolley connected to the mains would be carrying the full load of all the others. You wouldn't be able to have many trolleys in the "nest" before the load would exceed the rated output of the first trolley, blowing the UPS.

How about this:

Build a charging dock like the trolley shelters in supermarket carparks, but only one trolley wide. Fit 2 charging rails into the floor of the dock, or as strips each side of the dock (guide rails for the wheels?). Put 13.8v across the charging rails (this would be perfectly safe).
Put a pair of contacts on each trolley, so that they touch the charging rails when the trolley is docked.

Use the 13.8v to charge a car battery. Use the battery to run an inverter, that powers the laptop psu.
You could simplify things by using a battery pack that matches the output voltage of the laptop PSU. You could then do away with the inverter and laptop PSU - more efficient. You could even do away with the laptop's built-in battery.

I believe that it would be possible to charge the trolleys using inductive loops placed around the store and in docks, so that no physical contact would be needed.

[Kong]

yes i am trying to attach them to trolleys, the shopping trolleys they have in airports.

it isnt a real project as such, as in im not going to build them, its just the design and concept. im doing a product design course in university. The brief is to deign a shopping trolley with a new means of advertising.

i need this trolley to house a screen that can display adverts in the duty free area of airports. Im debating whether to use a wireless lcd screen, or use a laptop. the screen has to be a decent size to be noticeable and legible from a distance of at least 2m. so i was thinking 17-19in.

The trolleys have to display the adverts for as much time possiblewithout having to recharge. as you mentioned earlier if i could use inductive charging, with the charging hotspots placed in certain areas of the duty free then they could be charged as theyre being used. is this possible? are there any safety issues with this? what components would i need fitted to the trolley and what components would i need installed in the charging hotspot areas?

i like the idea of inductive charging with the rails that you mentioned. i did think of having something like this but didnt have the knowledge of how to follow the idea through and ultimately if it would work. With the trolleys on the rails are there any safety issues with having exposed contacts? do you know how long it would take to charge the battery?


if you could please provide me with more details, maybe some websites or actual components i could buy that would make it work, that would be much appreciated. thank u so much for your help, and if you could help me further with the electrical aspects of this project i would be soooo grateful!

[clockworks]

I've got no experience in this area, I'm just using common sense and guesswork!

Your best bet for the screens would probably be "tablet" PCs. They have all the hardware you need, and you don't have to worry about what to do with the laptop keyboard.

Using a low voltage rail charging system would be perfectly safe - think about slot-car tracks (Scalextric), they're safe for children to use.

Lead-acid (car battery) manufacturers recommend charging at 10% of the nominal capacity. A full charge would take 10 hours.

I've no idea how efficient inductive charging would be, it's just something I read about somewhere.

I think one of the major supermarket chains was thinking of running a similar project, maybe Tesco or Sainsburys?