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Old 09-30-2009, 09:46 PM   #16
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Eliminate Dead Batteries in Thermostat


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Lots of folks know the answer, I guess...! Like pro installers and pro DIY'rs. But, large doses of humor (as were detected in your original post) would take away from the "Mission" of this website. Which is to help each other and share and acquire knowledge and experience!.... (Not Really)!!!
umm...don't worry, I will take your advice and either have a pro do it or maybe search for a power stealing thermostat that would foot the bill.

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Old 10-01-2009, 06:54 AM   #17
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Eliminate Dead Batteries in Thermostat


The batteries are used only to power the display.
The t stat works from the 24 v supply of the heating/cooling unit!

Change batteries twice a year when you change the clocks!
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Old 10-01-2009, 12:09 PM   #18
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Eliminate Dead Batteries in Thermostat


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I believe these batteries provide 1.5V DC a piece...correct????
http://en.wikipedia.org/wiki/AA_battery

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Old 10-01-2009, 12:18 PM   #19
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Eliminate Dead Batteries in Thermostat


I've always wondered why they needed batteries....instead of powering the display from the 24v
Maybe 24v is too much...but surely they could step it down
But that might make the thermostat more expensive
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Old 10-01-2009, 04:20 PM   #20
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Eliminate Dead Batteries in Thermostat


I thought the batteries were to supply keep-alive current for the program memory and to keep the clock running.
It may take only a few mA. The current flow will drive the design since the voltage can probably vary from 2v to 3v.
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Old 10-01-2009, 10:10 PM   #21
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Eliminate Dead Batteries in Thermostat


It would be very easy, and completely safe, to design a circuit that replace the batteries in a thermostat. All you'd need is a couple of diodes, a regulator chip, and a capacitor. It'd all fit in the existing battery compartment.

The only trouble is that each time the power failed for more than a second or so, the thermostat would need to be re-programmed.

Rob
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Old 10-01-2009, 10:14 PM   #22
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Eliminate Dead Batteries in Thermostat


I just aquired a new Honeywell thermostat that is powered by 24 vac from the furnace. It does have a lithium battery (about the size of a 5 cent coin) that is used to maintain the program memory. These batteries last for years!
In my case the tech found an extra wire in the cable to feed the 24 volts to the thermostat.
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Old 12-13-2009, 09:26 AM   #23
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Eliminate Dead Batteries in Thermostat


Well...squeezing more days out of my rechargeable batteries meant they died last nite
Problem is if you do not drain them fully the do not charge right

And the display does switch the heat on/off
So no batterries = no heat
It was 65 when I went to bed at 11:30, about 58 when I woke up around 8 (?)

Time for some new rechargeables...most of mine are 3 years old & not lasting very long any more
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Old 12-13-2009, 12:45 PM   #24
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Eliminate Dead Batteries in Thermostat


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Originally Posted by Scuba_Dave View Post
Well...squeezing more days out of my rechargeable batteries meant they died last nite
Problem is if you do not drain them fully the do not charge right

And the display does switch the heat on/off
So no batterries = no heat
It was 65 when I went to bed at 11:30, about 58 when I woke up around 8 (?)

Time for some new rechargeables...most of mine are 3 years old & not lasting very long any more
Wouldn't it be best then to use Duracell or some equivalent high quality Alkaline batteries that last long and give you a warning when the battery is running low. The rechargables have too many preconditions and stipulations, sometimes. And they don't last much longer than a regular, hi-qual battery. (No matter what) Don't Drink and Drive, Ever!!!
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Old 12-13-2009, 01:15 PM   #25
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Eliminate Dead Batteries in Thermostat


It was saying battery low for several days, if not a week - my bad
I'm going thru my rechargeables & seperating out the ones that are old/no longer charging fully

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