Using a d cell battery to power a digital watch?

That battery holder could be part of the problem. Is there any movement of or shock applied to the battery holder when it is supposed to be helping power the watch? Brief opens would well explain the symptoms you report.

I am reasonably sure that your solid wire preference is an example of the "Post Hoc" fallacy. If interested in that, see

If the solid wire actually did "fix" the problem, it was because you had to change your connection technique, and the new one works better.

That is conceivable if you have made some huge loop, separating members of the wire pair. You didn't do that, did you? If not, RFI is not the problem.

I think you just need to get power to them on a continuous basis, not even briefly interrupted.

You're welcome now.

Besides the good advice others have given, consider that these watches typically use LCD displays that are not soldered in place but are simply held against a strip of contacts. It's pretty easy to dislodge this, and I've seen plenty of cheap units where the watch behaves just as you describe. I suspect that may be one reason why they are discarded by others in the first place!

Best regards,

Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis

Thanks guys! It's better to be a brief open in this case rather than an antenna issue because this way I can fix it with a better electrical connection instead of trying to shield the power conductors. I am going to resolder the device I am most interested in so that the wires (will use stranded) are soldered directly to the device's internal wires instead of to the coin cell pads/connectors. My solder connections seemed perfect but will try the previously mentioned fix. The other devices I have can wait. I will probably post my findings here. It will be good to know if my stranded wire is good or not. Thanks again, later guys!

I think a AAA battery will last as long or longer than a "D" cell, since both have the same shelf life and the watch draws very little power. Probably not enough to drain a AAA battery during it's shelf life.

Why waste a "D" cell when you can get the same performance from a AAA cell?

-Bill

Actually, the OP mentioned it. But yes, recharagable batteries of any variety are a waste for a digital clock/watch application. Alkaline AAAs are the only way to go. Or maybe Lithium for longer shelf life, but those are more expensive.

I ran a quartz wall clock for 3 years using 5 salt water cells in series. I used 5 small olive jars with a strip of copper and aluminum inside submerged in salt water. Gave me about 300 mV per cell at a couple milliamps, but I got tired of adding water to the cells every week or so to make up for the evaporation.

-Bill

| >> I have been powering them with wires soldered to the | >> correct polarity on the watch contacts and using | >> battery holders bought from radio shack to power | >> the watches with d cell batteries (rechargeable | >> alkaline in some cases). | | I think a AAA battery will last as long or longer than a "D" cell, | since both have the same shelf life and the watch draws very little | power. Probably not enough to drain a AAA battery during it's shelf | life. | | Why waste a "D" cell when you can get the same performance from a AAA | cell?

Agreed, a AAA cell would probably last years.

However, you mentioned a rechargable alkaline? Big waste. I don't know what the discharge rate on those are, but a NiCd would be dead in six months, and a NiMH cell in under 3.

I love my rechargable batteries and buy them in large quantities, but I also know that there's applications that they don't work well for due to their relatively high self discharge rate -- remotes, smoke alarms, emergency flashlights, etc.

On a related note, my trick is to take 9V batteries that are "dead" at 8V, and make a tiny 3V regulator that sits on a battery clip. I have a menagerie of clocks, kitchen timers, calculators, etc, with 9V batteries stapped to them. It takes a ***long*** time to drain a "dead" 9V down below 3V... and dead 9V batteries are free!

The regulator uses an LED with a large series resistor as a super-sharp low-voltage Zener, plus a simple pass transistor. Works great, and totally impractical... I love it!

Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis

Interesting stuff. I am pretty sure a rechargeable alkaline battery has a longer shelf (charge) life than rechargeable nicads or rechargeable nimhs. I am using a rechargeable "d" battery simply because it is handy. I don't like traveling across town in this tourist town risking my life every time with those other drivers. I appreciate the answers - especially the one about solder connections and nickel or stainless steel contact points. I soldered directly to the power supply wires in my aqua reminder and it works perfectly now and the same with the bicycle odometers. So it was a poor electrical connection, good mechanical connection that I had previously. This project is practical to me much like my other previous project I haven't finished yet. That was to make a rechargeable battery pack for a smoke alarm and before you scoff and say that wouldn't be reliable keep in mind I have seen fire alarms using that exact same method and that fire alarm was a first alert brand. The only reason I didn't buy it when I saw it is because it was used, I might very well do some searching right now for new units of those and might order one. The one I saw is directly wired to the house' power supply (~115 volts). Thanks for telling me that the solder connection was a poor electrical connection but a good mechanical connection when it comes to stainless steel and nickel, that solved my problem perfectly - Later!