Crappy desk clock

[candleghost]

So I bought a desk clock recently for my new place, it looks decent and serves it's purpose... except for one thing, it drains it's 3xAAA battery supply in 4 days flat. Needless to say that's a big pain and made me want to chuck the thing right into the trash can... but I'm hoping there's a way to salvage it. It would be worth it for me to modify this thing with a portable power supply that could last a month or so before recharging, that would be plenty enough for me.

The clock has an optional power input that consists of a 5V AC/DC USB wall wart, but I can't plug it into a wall because it resides on a coffee table in the middle of the room. I have an Anker portable charger rated at 13000 mAh which I plugged it into, but it only powers the clock when I initially turn the battery pack on, when it goes into an idle state the clock turns off again. I'm not sure why that is, maybe it's not drawing enough power to be recognized as a device?

I tried searching the net for any tutorials about powering a device through USB via LiPo but I keep getting results that aren't relevant to what I'm after, and while I'm a fairly technical guy I'm a total newb when it comes to electrical.

Do you guys know of any battery packs tailor made for this kind of project, or would it be easy to create a solution that won't burn my new place down? Any links to products or existing tutorials would be greatly appreciated, and if you require further info, I'll provide it. Thanks.

 

[kellys_eye]

Zeroly, what kind of clock? Digital, analogue.... link to a website perhaps?

Firstly, what type of AAA cells are you using? Cheap'n'cheerful or pukka? The capacity of such cells varies enormously and you most often get what you pay for.

Secondly, are you sure there isn't some additional function (backlight maybe?) that's draining the batteries? Backlights are generally only used for 'instant' use and not meant to run continuously.

If the batteries are 'decent' and everything else is ok then using three D-cells (or even C-cells) in the appropriate holder would be a good enough solution - bit bulky but maybe you can incorporate them into a plinth that the clock could stand on?

 

[candleghost]

The clock is digital with LED display, the batteries should be fine, they're proper Duracell. As far as a backlight, there doesn't appear to be any control that I know of and the manual is poorly worded/translated from Chinese... big shock there.

The coffee table it resides on is the storage type, which means I can tuck a battery pack plus cable under the lid, that's not a problem. Since the unit comes with a USB input cable, it would be most convenient to run that to a pre-config'd battery pack, I'm just not sure if there is a limitation as explained above with the unit turning off, maybe it's not actively drawing current?

 

[davenn]

The clock is digital with LED display, the batteries should be fine, they're proper Duracell. As far as a backlight, there doesn't appear to be any control that I know of

if it is a LED display, it shouldn't have a backlight .... doesn't need one
LEDS will be hungry on power compared to a LCD display

 

[kellys_eye]

Most permanently-lit LED clocks are mains powered for the obvious reasons..... if you think back (or are old enough to remember them) LED watches used to require the user to push a button to momentarily light the display to conserve battery power.

Even using a multiplexed display such a clock will consume some 10's of milliamps. A typical (good) AAA battery will have a capacity of around 1000mAhr so if your clock uses 20mA it will flatten the batteries in 50 hours...... it will have stopped well before then due to falling voltage.

 

[candleghost]

Looks like all I needed was a lipo that can run on low current without an automatic shut off feature. Ordered a fairly cheap model that fits the bill rated at 13000mAh. I guess I'll see how long it lasts!