Our Friend the 9 volt battery

9V batteries and electronic projects

First, holding a 9V battery securely is important, especially for portable gear.  Originally I'd use commercially sold clips like this stainless one from Keystone:



But they are somewhat expensive and require some method of attaching them to the enclosure (here nailed into the top of a piece of wood on a test fixture) that won't have too high a profile and make the battery stick out of the holder.  Finally as can be seen with this steel cased alkaline battery, the metal clip will scratch the battery:


 

  So I changed to a new method using a cable tie with a screw hole:


Now a single 6-32 sized nut/bolt will hold the battery to the enclosure.  The cable ties are inexpensive (about a nickel each quantity 200 on Ebay) and will hold the battery in place without scratching the paint.  Also it's easy to change from horizontal to vertical orientation.  Note that 9V battery dimensions vary quite a bit so don't cinch the cable tie too tightly.  It just has to be tight enough to prevent the battery from sliding around.

To allow easy mounting cut the tie end flush to the other end with the hole as shown here:



Second, connecting to the battery is also important.  I used to use these soft 9V snaps:

but they don't last:  I changed to the sturdier hard backed snaps like this:



 

As mentioned in previous blog posts, I'm a Ten-Tec / Heathkit fan so I reserve the right to use RCA plugs and jacks inappropriately :)


Third, which battery to choose ?  Alkalines were always my favorites, especially old ones from beeping smoke alarms, not enough oomph to sound an alarm but still plenty of life for ham projects like a keyer.  But they do bulge and leak like all depleted alkalines eventually will.  So I started using the Tenergy Centura NiMH 9V batteries:


These are made with low self discharge cells and come precharged.  Similar characteristics to the highly favored Eneloops, they measure about 9.75 volts when charged and push the meter needle well into the "green for good" on the VOM battery test.  I also use them in smoke alarms.  The only bad thing to report is the Tenergy 9V charger, it's electrically (RF) noisy like many modern electrical items.  The noise is modulated by the blinking LED, so at least when the pulsing hash on the radio stops you know that the battery is charged :)

Tenergy also makes these NiMH in AA sized cells.  Be sure to get the Centura cells/batteries - Tenergy also sells cheaper NiMH cells that don't have the low self discharge feature.


Best Regards,
Chuck, WB9KZY
http://wb9kzy.com/ham.htm