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aurgathor

join:2002-12-01
Lynnwood, WA
kudos:1
reply to cowboyro

Re: Electronics that stop working when cold

said by cowboyro:

said by sergey3:

But under load the battery will produce less power (fewer amps).

That without doubt. But then the power requirement of a pressure gauge isn't that big to start with...

But that extra resistance may decrease the output voltage enough to cause the gauge to malfunction. I had a similar issue (and I did my own troubleshooting to find the culprit -- Subaru, that's a hint for you ) where the battery played an important role. See: »Highest voltage 2032 battery

Of course in my case the root cause was an improperly designed circuit that required 3+ volts to function properly instead of going down to 2.6 - 2.7V.
--
Wacky Races 2012!


cowboyro
Premium
join:2000-10-11
Shelton, CT

said by aurgathor:

But that extra resistance may decrease the output voltage enough to cause the gauge to malfunction.

I'm still willing to bet on either LCD or the gauge refusing to work outside a temperature calibration range.
But I guess the voltage drop is something that I can easily test...

lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1
reply to aurgathor

said by aurgathor:

Of course in my case the root cause was an improperly designed circuit that required 3+ volts to function properly instead of going down to 2.6 - 2.7V.

Typical "3V" CMOS chips are actually designed to accept VCC = 3.3V +/- 0.3V. So the lower end of acceptable VCC is actually 3V which may be higher than a partially discharged CR2032 battery.

Now, the current drawn by all CMOS chips increase with lower temperature, so VCC could go down even more than acceptable range.

Solution is a buck-boost DC-DC converter IC to supply stable 3.3V from a single CR2032 cell. But that of course will cost an extra buck or two.


aurgathor

join:2002-12-01
Lynnwood, WA
kudos:1

said by lutful:

Typical "3V" CMOS chips are actually designed to accept VCC = 3.3V +/- 0.3V. So the lower end of acceptable VCC is actually 3V which may be higher than a partially discharged CR2032 battery.

So in this particular use, they should be using a custom CMOS circuit designed to work with 3.0V +/- 0.3V, which more closely matches the CR2032.

I guess I need to take apart my gauge to see what's in it.

Solution is a buck-boost DC-DC converter IC to supply stable 3.3V from a single CR2032 cell. But that of course will cost an extra buck or two.

And would also decrease efficiency.
--
Wacky Races 2012!