Seeking a battery operated wall-mount LED clock

March 15, 2020 3:50 PM

I've been trying to find a battery operated wall-mount LED clock, and have found the search much harder than I'd expected. Can you help? Parameters within.

Requirements:

Most importantly, it is actually battery operated. Every one I've seen uses a battery to keep the time in case of a brief power outage, but requires an ugly cable during normal operations.

Equally important, it is bright and high contrast (ideally old-school bright red 7-segment LED on black background).

It should be ... big? At least a 4 or 5 inch tall numbers. A bit bigger if the price works would be fine. This is for indoor use so it doesn't have to be a billboard.

Preferably just hours and minutes. Depending on design, I could put up with more than that, but many of the corded designs I've seen are made worse by including seconds, the date, am/pm, etc.

Preferably not incredibly expensive? I was kinda expecting to find something reasonable for $50 and instead I'm seeing pretty poor options (with lots of negative reviews indicating broken on delivery / failed within a week / etc) ranging from like $80 to $300+, which seems excessive.

I've been kinda shocked at how hard this search has been (particularly the battery operated part, but also so many of the options are only from super shady sellers on Amazon with obviously photoshopped product photos, etc). Help me, AskMe!

posted by tocts to Shopping (7 answers total)

Here's the thing. LEDs are power hungry. A single decently bright LED is going to draw about 5ma at about 2 volts. Which is 0.01 watt. Four seven segment digits, assuming half of them on, is 14 LEDs, or 0.14 watts. Over the course of a day, that's 3.6 watt-hours which is equivalent to 3600mah, or about the power capacity of a single good quality AA rechargable. If your clock takes 4AA batteries, it'll run for about four days before it needs the batteries charged (assuming you use rechargables, because buying new alkalines every week will break you.)

Note that larger 7-segment LED numbers often have 3 actual LEDs per segment so that they're bright enough to be seen in room light. Which will treble the power requirement.

There's a reason why LED watches like the "Pulsar" model from the 70s only lit up when you pressed a button. Because LEDs are just nuts with power.

Anyway, that's why you can't find a LED clock that doesn't plug into the wall.
posted by seanmpuckett at 4:03 PM on March 15, 2020 [3 favorites]

As the childhood owner of a Pulsar watch, I concur entirely with seanmpuckett. An analog(ue) clock, on the other hand, will go for as much as a year on a single AA cell; it can be quite large, is high-contrast and easy for most people to read. Many come without a second hand, and they're pretty quiet. There's a reason you find battery-powered analog(ue) clocks in homes and offices the world over. I've always wanted to build my own big LED wall clock, and probably will at some point, but it would have to be connected to a 'wall wart'.
posted by pipeski at 4:18 PM on March 15, 2020

(actually a rip-off Pulsar, of course)
posted by pipeski at 4:20 PM on March 15, 2020

Response by poster: I understand that battery operated may simply not be in the cards. That being said, I would still appreciate suggestions for wired versions that people actually had good experience with, if possible. Still very much focused on an LED option, because while I know analog clocks are far more abundant, and while I can read them, I know that I simply don't register them as quickly as I need to for this application (which is primarily keeping me honest with time in my home office, making sure I'm not suddenly realizing it's 2 hours later, etc).
posted by tocts at 5:38 PM on March 15, 2020

What about an LCD clock instead? They use a lot less power. Some have a backlight
posted by ShooBoo at 5:55 PM on March 15, 2020 [3 favorites]

Well, we use an old mobile phone with a big digital clock app running on it 24/7. It's plugged in, of course, but sits sideways with a slight lean back on a nice wooden stand and isn't out of place among the funiture. There's a couple advantages: it self-adjusts for brightness, and it's always exactly on time because of time server updating. You can find apps with myriad display options, but we just use a simple 24-hour "flip clock" face that's extremely easy to read.
posted by seanmpuckett at 6:28 PM on March 15, 2020

As others have noted, LED's are rather power hungry.

But if you're not locked into LED's, how about a flip clock? The digits are about 5" tall, and it runs on a single "D" cell battery. This one's a wall mount, but there are desktops.
posted by Marky at 12:22 AM on March 17, 2020 [1 favorite]