On Wednesday, October 1, 2014 11:58:24 AM UTC-4, Pico Rico wrote:
"trader_4" wrote in message

...

On Wednesday, October 1, 2014 11:12:28 AM UTC-4, Pico Rico wrote:

"trader_4" wrote in message



...



On Wednesday, October 1, 2014 9:33:57 AM UTC-4, dpb wrote:



On 10/01/2014 7:47 AM, trader_4 wrote:







...















... since these are both AC and battery powered, why does the

battery







go out in a year, just as fast or faster than battery only powered



ones?







...















'Cuz they're a poorly designed (read "cheap to build") and don't







actually cut the battery (completely) out when A/C is on nor use







rechargeable batteries would be the likely cause...















I've not looked, but I'd think such a unit would be readily available







altho undoubtedly at a somewhat higher price point. There are just

the







minimal one each floor of the old battery-powered type here as

nothing's







been modified since all the recent Code changes. So, that's just

three







and the once't a year deal isn't so bad as there are no cathedral







ceilings, etc., ...















--







A diode that costs maybe 10 cents has a big impact on price?







think of the voltage drop, too.



I don't see .6V diode drop from a 9V battery being a design challenge.

The electronics is going to work on 5V or 3V anyway.



but the battery will "die" sooner.

How so? The battery is rated at X amphours. Whether it delivers it through
a diode or not is mostly insignificant. Only a very small amount of power is
lost in the diode.