How do you change a battery?

Post by **Eric D** » Mon Dec 14, 2009 12:31 pm

I have been driving for close to 15 years and I have never had to change a battery. Well, my wife's car needs a new one, so I went out and got one and now I need to put it in.

It is on a charger right now to "top it off" so to speak. I don't know if I need to do this, but I figure it cannot hurt.

How do I replace the one in the car with it? I don't want to loose any settings on the radio, or the programming on the remote start, so I had planned to start the car first, pull the old battery and then put the new one in and after a bit shut the car off. (All the while making sure not to touch the (+) lead to anything metal!)

Now in the past people have told me the car won't run without the battery in it, but I find that to be total crap, as when the car is running it gets its power from the alternator, not the battery. My only fear is the regulator relies on the battery for some measure of filtration and by removing it while the car is running I risk damaging AC hitting one of the "computers" in the car.

Post by **stipud** » Mon Dec 14, 2009 12:58 pm

I know many mechanics who use the technique you describe. I have not heard of a case of it failing from any one of them. But of course as you said, there is potential for a voltage spike that could damage your car's fragile computers. So while it is possible, I have personally weighed these options myself, and I always end up doing it with the car off and redoing my settings. 5 mins reprogramming beats a fried car, even if the likelihood of an issue is small.

phonixx · Post by **phonixx** » Mon Dec 14, 2009 1:17 pm

I new cars i think they put some kind of 12V source in the cigarette lighter hole while changing the batteries to unvoid any problems with the car losing the current. I guess its enough with a small 12V batteri or you can use a small "start helper"

Post by **Eric D** » Mon Dec 14, 2009 1:27 pm

The cigarette lighter idea is an interesting one.

If it were just the presets in her radio I would not care, but I did not install the remote start and to program it I need to set up a time with my buddy to get it over to him and redone. I am curious what time frame I have until the remote start looses its settings, seconds or hours? It really bothers me they don't use something like flash to permanently store the programming, but then again maybe it does and I just am used to the really old units from the 90's.

bretti_kivi · Post by **bretti_kivi** » Mon Dec 14, 2009 1:35 pm

I think so. No way I would change a battery on a running car. Mine will retain most stuff for 30 mins or so, the tripmeter for 10 or so, I think, I can't remember.

First off neg off, then + and replace in that order. Shouldn't take long, depending on the state of the tie-downs.

Bret

Post by **stipud** » Mon Dec 14, 2009 3:08 pm

Eric D wrote:The cigarette lighter idea is an interesting one.

If it were just the presets in her radio I would not care, but I did not install the remote start and to program it I need to set up a time with my buddy to get it over to him and redone. I am curious what time frame I have until the remote start looses its settings, seconds or hours? It really bothers me they don't use something like flash to permanently store the programming, but then again maybe it does and I just am used to the really old units from the 90's.

I have not had any modern (in the last 10 years at least) alarm lose its programming from disconnecting the battery.

Post by **Bfowler** » Mon Dec 14, 2009 5:04 pm

if the new battery is on a charger, you could connect the charger to the positive and negative wires on the old battery, then remove both wires and move them aside while insulated. that should create enough charge to keep your settings. then swap batteries and reconnect.

audiophyle_247 · Post by **audiophyle_247** » Mon Dec 14, 2009 7:16 pm

+1 for the cig lighter trick.
Last shop I worked at has a booster pack for jump starting cars that has a cig adapter that puts 12v through the cig circuit.
With the car off there is very little current draw, far less than the cig fuse rating under the dash of pretty much all cars. It actually keeps everything energized while you replace the battery and nothing looses memory.
Its mostly used to avoid needing radio codes.

I strongly advise against unhooking the battery while the car is running, it is a very easy way to mess a lot of things up.

You can also hook the new batt to some jumper cables, unhook & remove the old batt, slide the new batt in place, reattach the terminals, and remove the jumper cables.

bladestars · Post by **bladestars** » Tue Dec 15, 2009 2:37 pm

What about us with diesel trucks? Dual batteries !

Post by **Jacampb2** » Tue Dec 15, 2009 3:27 pm

If you do the cigarette lighter trick, make sure you have a car that has constant power to the lighter. A lot of "accessory" sockets, and foreign cars have switched power to the lighter...

As for diesels, most light trucks are still 12V systems, the two batteries are in parallel. Sometimes relay isolated, sometimes not. If it is new enough to use a isolator, my recommendation would be to switch the key to run, not start, and swap one and then the other. The secondary battery should be plenty to maintain the memory while you swap out the primary, and visa versa...

Post by **Eric D** » Wed Dec 16, 2009 9:11 am

Well, I ended up changing the battery with the car off, and the remote start did not loose its settings, but it did start the car as soon as I connected the new battery, which scared the crap out of me, and I think is a safety hazard.

The new battery is 12.58V, and the old one was 12.25V. That seems low to me, but since the car started just fine I am thinking I probably did not even need to change it in the first place.

bretti_kivi · Post by **bretti_kivi** » Wed Dec 16, 2009 10:14 am

depends. Voltage without load doesn't really say much....

Bret

Post by **joerg** » Wed Dec 16, 2009 11:34 am

I usally changed my batteries when their voltage dropped below 11,5Volts. The first sign that it wouldn´t make it through the austrian winter.