Replacing battery "ahead of time"?

[katapaltes]

So... Took a friend's car to an independent garage to see if it could be repaired or if it was time to buy another. Owner came highly recommended and seemed knowledgeable. He mentioned that he replaces batteries on all his cars before they fail, and he never has any electrical problems. (No issues with coils, etc.) He said that as voltage drops over time, more amperage would be supplied, which makes sense since Watts = Volts x Amps...

Even if his rationale is wrong, should one replace batteries on schedule instead of waiting for a slow start to run to the car parts store (which is what I do). Should one check voltage periodically along with oil level, etc?

When I heard this advice, I immediately thought of you guys..

 

[katapaltes]

Nobody?? I was sure @pcb would be all over this...

 

[pcb]

Well, all I can say is that I've had the same battery in my car since I bought it 9 years ago and it wasn't new then.

Everything that guy mentioned makes sense to me but my car hasn't had any electrical problems although it does turn over really slow in the winter but always starts.

I found this sticker on my battery.




I think my battery is from September 2008.

 

[pb4ugotobed]

I've never heard of such a thing. That's just silly.

The only time voltage would be low is for about a half a second during the biggest part of the dip while cranking the engine. And voltage is going to be low even with a brand new battery.

Once the car is running, the alternator takes over and you're running mid 14 volts. good battery, bad battery, or no battery at all. Why would an old (good) battery make any difference if running voltage is the same if you take the battery completely out of the car?

I never once replaced a coil on my P5. It still had the original 2002 coils on it that the car was built with. It came with a cheap walmart battery that died a few weeks after I bought it. I replaced it with another $44 cheap walmart battery that worked until the day I sold it.

Aside from that, automotive electronics are designed to work within a voltage RANGE. Most OEM Manufacturers (and aftermarket) will specify nominal operating voltage from ~8v-16v, but during the development process, the parts themselves are tested to even higher, and lower voltages, reverse voltage (hooking power and ground up backwards), and all sorts of other stuff to make sure they still work after all that, and performance is not degraded before the parts are approved. This would apply to most any electronic part in any car. Again, disproving your friend's theory that replacing the battery for "preventative maintenance" does anything at all.

 

[katapaltes]

I don't know how some folks get such good service from their batteries. Mine die like clockwork every four years during the summer here in Texas. I get one slow start as a warning, and I know that the next destination needs to be my home. Even the original battery did this, which was probably better quality than the Autozone ones I've been using since. (The only reason I get batteries from Autozone is that they die ahead of time and I get a reasonable credit by going back there.)

I have a friend here in Dallas with a VW Jetta that's almost ten years old and she's on her original battery. The battery is probably the best part of that car's electrical system based on what I've heard about VW's electricals over the years...

Based on what PB4 said above, I won't replace my battery ahead of time - unless someone else is using the car and I can't afford for them to be stranded.

 

[pcb]

I'm a complete electricity miser with my car.
The alternator only puts out a maximum of 77 amps at 2,000 rpm and only 59 amps at 1,000 rpm.

I don't like to pull power out of my battery. It's the cycling between charging and draining that wears out a battery.
I only operate one window at a time, (the owners manual says any more than two windows at once can blow the 100 amp main fuse.) and I turn off my interior fan while my rear defog is on.

I turn off all unnecessary electrics about 10 minutes before I shut off my car to help the battery charge as fully as possible.

I also have a small solar panel installed under my sunroof to help keep the battery topped up.

I check my battery at least once a year and top it up with distilled water. (maintenance-free batteries are fricken stupid. You can't maintain them... You have to buy a new one.)