On Wednesday, October 1, 2014 2:02:54 PM UTC-4, Pico Rico wrote:
"trader_4" wrote in message

...

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.



The voltage without a diode can drop ..65v further and still power the unit.

Wow, really? How very important. Let's see, we have a smoke detector
that's primarily operated by AC. So, it can go forever on AC plus last
about as long as a battery operated one if the power goes out. Power
almost always goes out for hours or a few days, not a year or two. That
voltage drop is important again, why?

I've also cited other common devices where they have battery plus AC and
don't draw the battery down unless it's needed because the AC fails.