Keeping car electronics alive while changing battery - homebrew approach?

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I need to clean the terminals and change out my car battery. I would rather not lose the setttings on my radio. But I also would rather not invest in a charger just for this application.
I have several variable voltage DC power supplies (supplying about 1A). Could I use such a supply set at say about 13-14V to supply temporary power while the battery is removed?
Other than getting the voltage and polarity right, anything to be worried about here or any chance of causing damage (to either car electonics or to my power supply)?
Thanks
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A cigarette lighter adapter and a 9V battery ought to work with most cars, IIRC.
Joe
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I use a little 12v gel cell, thats what I had handy.
Jimmie
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Joe wrote:

Firmware does not need power to keep the contents. Other learned parameters can e relearned after battery is reconnected. Couple fill up and some usual driving will be all that needed.
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wrote:

VERY wrong on modern cars.
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I had to do this on my father in law's cadillac where the whole car gets a brain transplant when you disconnect the battery. I just connected it up to my car with jumper cables, swapped the battery and hooked it back up. Just be careful not to let anything short out. This caddy has a "jumper" terminal away from the battery so the hookup was easy. I just put the terminals in heavy leather work gloves because I had that handy.
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snipped-for-privacy@aol.com wrote:

This sounded a little like overkill, but is sounding better all the time.
No worry about cig lighter is on, or door is open for lights. And (not mentioned except by you) disconnected hot battery terminal can't be grounded.
Temporarily connecting a 9V battery to 12V doesn't do anything?
--
bud--

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wrote:

If there is an under hood light, like that caddy has, a 9v battery would not do diddly. Jumper cables to another car seemed the fastest/easiest thing to do since they were already in my trunk.
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On Fri, 26 Mar 2010 16:51:40 -0400, snipped-for-privacy@aol.com wrote:

That must explain why every auto parts store in creation sells a device for this purpose that uses 9 volt batteries.
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snipped-for-privacy@nowheremonfrere.com wrote:

And how long does it take to pull the bulb out of that underhood light?
--
aem sends...

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bud-- wrote:

That depends on what the voltage requirement of the Non-Volatile RAM. Lot's of auto computers run partially on regulated 5 volts powered by the 12vdc battery. If so, the 9vdc would work just fine. Not to mention that most non-volatile ram doesn't need full rated working voltage to hold memory. I've seen lots of 5VDC ram that only need 2.5 to 3 volts to hold the memory.
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Set the voltage at 14.0 +/- 0.25V and you should be fine. Like you indicated, just keep the polarities correct.
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On 3/25/2010 5:00 PM hr(bob) snipped-for-privacy@att.net spake thus:

Sounds like way overkill on the precision (and voltage) to me. Someone else here said to just use a 9-volt battery plugged into the cigarette lighter socket (does this car even have one of those???). 9 volts might be a mite low, but I'd say just use a 12-volt supply and be done with it. Remember, you're not charging the battery, only powering the radio's NOVRAM stay-alive power.
--
You were wrong, and I'm man enough to admit it.

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wrote:

turn on interior lights and suck down the battery.
Charlie
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wrote:

what if your car turns off the cig lighter outlet when the car is off? Will the 9v fixture still hold the memory?
--
Jim Yanik
jyanik
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Jim Yanik wrote:

Most don't turn off the cigar lighter. Although I do question what happens when the door is opened and the little 9v tries to power the interior lights?
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Tony wrote:

all 3 of my cars do: a 90, 94, and 96.

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chaniarts wrote:

it a 'power outlet', and it has a little flipper cover over it. Some switch, some don't. Usual convention is a picture of a battery for non-switched, and a picture of a key for switched. A lot of cars don't even have one. Other alternative is to go to Harbor Freight, and buy some big alligator clips and some wire, and just make it so you can clip it on the next connector and available ground point downstream from the battery.
--
aem sends...

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Eat a lot of beans. Then make big farts into the engine.
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My truck and car each have two power outlets. One of the ones in my truck is a "cigar lighter" and one is an aux power outlet. IIRC, one is switched, but I don't remember which one. Neither of the outlets in the car is switched.
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