Converting 12v to household battery

Stephenlittle

Joined Nov 1, 2021
6
Hello
Just joined and apologies for what you probably think is a stupid question.
I have a vintage Dashboard clock (Smiths), which is 12v I would like to power this through battery and make into a desk ornament. Any help would be appreciated.
Thanks
Stephen

ericgibbs

Joined Jan 29, 2010
15,347
hi Stephen,
Welcome to AAC,
Do you want to power the clock by mains supply or battery, or perhaps both.?
E

Stephenlittle

Joined Nov 1, 2021
6
hi Stephen,
Welcome to AAC,
Do you want to power the clock by mains supply or battery, or perhaps both.?
E
Hi E
Thanks for your reply, I was hoping for battery only.

crutschow

Joined Mar 14, 2008
29,489
I was hoping for battery only.
Then you need to measure the average clock current to determine the size battery you need, for how long you want the battery to last.

Is this the type of vehicle clock that uses a small solenoid to periodically wind a spring in the clock (thus you would hear a periodic sound from the clock when it wound every few minutes)?

Stephenlittle

Joined Nov 1, 2021
6
Then you need to measure the average clock current to determine the size battery you need, for how long you want the battery to last.

Is this the type of vehicle clock that uses a small solenoid to periodically wind a spring in the clock (thus you would hear a periodic sound from the clock when it wound every few minutes)?
Sorry but I don't know either

Joined Jul 18, 2013
24,991
I am guessing that is one of the old smith automotive clocks, they had a simple mechanism as @crutschow describes. You often had to give it a rap to get it going after working for a day or two.
There is not too many sources now for 12v battery of a suitable small size.
You have some degree of tolerance as the automotive voltage went up to 14.5v.

Stephenlittle

Joined Nov 1, 2021
6

Stephenlittle

Joined Nov 1, 2021
6
I am guessing that is one of the old smith automotive clocks, they had a simple mechanism as @crutschow describes. You often had to give it a rap to get it going after working for a day or two.
There is not too many sources now for 12v battery of a suitable small size.
You have some degree of tolerance as the automotive voltage went up to 14.5v.
Size of battery could be up to 8aa to give me room to play with

ThePanMan

Joined Mar 13, 2020
355
I can understand you wanting to power it from a battery, but I suspect it won't last more than a few days, maybe a week or two - depending on what kind of battery you use. If you're in the US of A then go to an Xfinity store and ask if you can have a 12 volt power supply. They get a whole bunch of them when people return modems. Gosh - I don't know how many of them I have, but they'll give you one or two for free. And they're typically good for 2 or 3 amps. You could wire in one of those and plug it in. Never have to worry about batteries or varying automotive voltages.

Joined Jul 18, 2013
24,991
There are several battery carriers for 8x AA out there, Amazon etc.

Stephenlittle

Joined Nov 1, 2021
6
I can understand you wanting to power it from a battery, but I suspect it won't last more than a few days, maybe a week or two - depending on what kind of battery you use. If you're in the US of A then go to an Xfinity store and ask if you can have a 12 volt power supply. They get a whole bunch of them when people return modems. Gosh - I don't know how many of them I have, but they'll give you one or two for free. And they're typically good for 2 or 3 amps. You could wire in one of those and plug it in. Never have to worry about batteries or varying automotive voltages.
Would anyone know of where to obtain these in the UK or Ireland ?

There are several battery carriers for 8x AA out there, Amazon etc.
I have seen these, but was unsure if they would work. I take it they wouldn't last long?

On the pic I posted, I take it the positive is the straight one not the one at an angle?

I can understand you wanting to power it from a battery, but I suspect it won't last more than a few days, maybe a week or two - depending on what kind of battery you use. If you're in the US of A then go to an Xfinity store and ask if you can have a 12 volt power supply. They get a whole bunch of them when people return modems. Gosh - I don't know how many of them I have, but they'll give you one or two for free. And they're typically good for 2 or 3 amps. You could wire in one of those and plug it in. Never have to worry about batteries or varying automotive voltages.

Joined Jul 18, 2013
24,991
On the pic I posted, I take it the positive is the straight one not the one at an angle?
It depends whether it came from a positive or negative frame auto.?
But if non-electronic it may not matter?

crutschow

Joined Mar 14, 2008
29,489
Would anyone know of where to obtain these in the UK or Ireland ?
You could buy a wallwort supply from one of the local electronic suppliers, like Farnell (example).

ThePanMan

Joined Mar 13, 2020
355
I suppose any local internet provider's outlet store where you can trade in an older unit for a more up-to-date unit would likely have them. I'm sure they won't reuse the old PS's, so handing them out occasionally shouldn't be an issue for them. Of course, someone smart could start grabbing a whole bunch of them and then provide them for a fee on something like Craigs List, or some other classifieds website.

Tonyr1084

Joined Sep 24, 2015
6,866
Yeah, I like the idea of grabbing a free 12V supply from an internet store. They're modem power supplies. I modified one to output 13.6V once. I made it to keep a battery at float charge. Occasionally I'd play a car radio from a car battery that was kept charged. However, not all are as easy to modify as the one I happened to choose. Some are a bit more tricky.

Your clock: The terminal that is screwed to the housing is the negative (provided it doesn't come from a car with a positive ground system) and the blade (straight up and down in the picture) is the positive. The one sitting atop that round protrusion is likely a lamp. You probably won't need that to be wired up. If you DID wire it up it would drain all your batteries in quick order. So you wouldn't want to utilize that part of the clock. You COULD put a momentary switch to light the dial face in the dark but you'd use it only for a moment. You will still shorten the life of the battery but only if you use it a lot.

Joined Jul 18, 2013
24,991
There are a few Youtube videos on Smith clocks out there, this one appears to be for a later type than yours but shows a need for correct polarity.
If you can open yours, it may be obvious as to whether it matters.

MisterBill2

Joined Jan 23, 2018
11,582
The one terminal with the round base is for the light, the other is for the winding current pulse. If you put the clock in a wood case you can have room for a small 12 volt gell cell that will power it for months before needing to recharge.