Shutoff adapter

Around here a battery "at rest" will usually stop around 13.2V

Cold climates will be lower, as you've found.

My new Q45 has seat "COOLERS" ;-)

And WARMERS also, just flip the switch, and set the temperature... actually pretty pleasant even here in AZ.

*** My December 2006 electric bill was 50% higher than my December 2005 bill. It's been unseemly cold here... the lime tree is struggling for survival :-(

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

Couldn't you trigger differentially by detecting the comparatively rapid drop in voltage upon switching off the engine (if there is any). Or by the sudden absence of ignition noise on the cig lighter socket.

robert

I wonder how fast it falls. Anyway, just to add a datapoint, my car's cigarette-lighter voltage was 14.7 volts warmed up after 20 minutes of hard driving. Jim commented that the charging voltage should be much lower at high temperatures. If this was the case, and a sufficiently-high threshold was chosen, the seat warmer would go ahead and shut off, even tho the engine was still running. But, the passenger compartment would be well warmed by that time and it would be OK if the seat warmer was off. So I still think a battery-voltage-clue scheme should work well.

Hmm.

Most modern alternators charge at somewhere between 14.2 to 14.8 volts. Somewhat higher than 15 years ago. JT has a couple of patents which baffle me: Temperature sensing to increase the voltage in cold weather and decrease it in hot weather. Makes sense for the batteries, however the temp sensor is in the regulator fastened to the alternator so all it does is reduce the charge voltage when the alternator gets hot. Nothing to do with the battery temperature (what have I missed Jim?).

Either way, the battery voltage will drop to about 13.8 volts *very* quickly, a minute or so at the most. Within 10 mins it will be down to

13.3 volts, then finally settle at between 12.6 and 12.8 (depending on battery type) but this last drop could take up to 24 hours. The voltages fall faster for wet cells than for gel or AGM.

The first drop from the charge voltage to about 13.8V could be used but the temp sensor in the alternator reg (they nearly all have them now) will often drop the charge voltage to around 13.5 volts when the alternator is hot (even if the batteries are freezing).

If you consistently have above 13.8 volts then the alternator is definitely charging. But less than 13.8 volts doesn't necessarily mean it isn't.

Shutting it off at say 13.2 might work. The worst ttat would happen is it might stay on for 10 minutes or so after the engine is turned off.

--
Gibbo

This email address isn\'t real.

No. In the '60's my spec was 15.1V cold, 13.3V hot.

I wanted to make the sensing part of the regulator part of the battery structure, just as LiIon cells are made today. But the car companies would have no part of it... might add 2¢ to the cost ;-)

Likewise I tried to sell a PWM approach (improves regulation and cuts radio noise dramatically) rather than the prevalent "hysteretic" approach... no dice.

I have lots of excellent designs that have never made it to market :-(

I even figured out how to measure the actual battery voltage though it's quite far from the regulator down the cable.

And my self-inverting CD ignition works super. Just about every technician who worked for me put it in their cars.

I used to argue with customers... cost me projects... now I give them whatever they want, no matter how stupid.

I tend to crawl under the dash and do it right.

Maybe even pull down a roof liner to pull cables.

I've even been known to drill a hole in the center of the roof to fit a BNC for the antenna for my 2-meter rig ;-)

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

Ahead of your time. Many from that period ran at 13.6 to 13.8 at 25degC. Most ran at that voltage regardless of temperature. At least that's the case in Europe.

That would make sense (a few do it now). But what's the point in measuring the alternator temperature? The alternator is always going to get hot so the charge voltage is always going to be to low.

Now commonplace. Especially on external regulators.

Now this I'm intrigued by. You going to tell?

--
Gibbo

This email address isn\'t real.

That would be _DC_generators_ ??

After market.

As soon as I can remember exactly how I did it ;-) I have the original paper designs around here somewhere. Something to do with the trough of the ripple.

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

Yes and alternators up to the mid to late 90s.

Partly, but many modern vehicles are now using PWM. A lot of them are PWMd from the engine management system.

Still intrigued.

--
Gibbo

This email address isn\'t real.