General > General Technical Chat
Car battery tests are of no value
<< < (3/4) > >>
tautech:

--- Quote from: joeqsmith on July 21, 2017, 01:55:21 am ---
--- Quote from: rstofer on July 20, 2017, 03:10:24 pm ---Around here during the summer it's HOT!  Car batteries don't like high temperatures so it is not a surprise when they fail during the summer.

Of all the batteries I have replaced over the last 30+ years, I would bet that every single one was replaced during the summer.

Seven years on a battery is pretty exceptional.  Even with quality batteries, I only get about 5 years.

--- End quote ---
Funny.  I can think of only one of our batteries that failed in the summer.  All the rest in the cold winter.

--- End quote ---
You just sometimes never know when an auto battery will crap out.
Some will last 10 years here but I've had unexpected failures at 4 years with zero warning and that's not funny at all if you happen to be out and about.

The only real trusted test of an auto battery is from a carbon pile tester, sure they're pretty hard on batteries but if they stand up to the draw off and not fall flat on its face you have some confidence that it'll be OK for a while yet.
deflicted:

--- Quote from: rdl on July 21, 2017, 03:06:38 am ---
--- Quote from: deflicted on July 21, 2017, 01:36:40 am ---
Here in California, we don't have the option of having batteries and alternators tested at auto parts stores. I tried Googling for the reason why, but the closest I got was that it has something to do with some California law that bans non-certified technicians from doing repairs (even for free), which apparently includes even simple diagnostic tests. Your choices here are pay a mechanic, or learn to test batteries and alternators on your own. Gee, thanks California.

--- End quote ---

I'd be willing to bet that being "certified" to perform those repairs in California requires little more than a hefty payment to the state for an official "license to repair" (which must be renewed annually of course).

--- End quote ---

I wouldn't take that bet. You're probably right about that. The weird thing is, trying to Google why California bans auto parts stores from performing free diagnostic tests is like trying to use Google to figure out who really killed Kennedy, or what's going on at Area 51. In this case, all I can find is lots of vague references on car forums to "something" happening in 2008 that caused all the auto parts stores to stop offering those services in California. Nobody seems to know what that "something" was. Nobody on any of those forum threads has managed to find any smoking gun in California law. Nor any news articles about it, etc.

Lots of speculation though. Some of the theories that people have come up with are:

* That performing diagnostics is tantamount to repair, and only certified repair shops can do that. However, no news stories about any auto stores getting fined or anything.
* That mechanics complained they were losing work due to the free diagnostics offered by auto parts stores
* That auto parts stores using untrained personnel to run diagnostics were steering consumers toward incorrect and/or unnecessary repairs
* That auto parts stores had been successfully sued in California courts by consumers for giving erroneous test results (i.e, you said my alternator was bad and it wasn't)

By the way, I misspoke. You can still get a battery tested and even charged, apparently. But alternator testing, as well as OBD2 code scanning, etc, are all banned. Basically anything that could be construed as repair. Also, we're apparently not the only state that has this ban. Check any of the major U.S. auto parts chains' websites, and they all say "Except in California and Hawaii, where it is prohibited by law."

As annoying as it is that California thinks I'm too dumb to take some pimply faced AutoZone employee's diagnosis of my alternator with an appropriately sized grain of salt, the real annoying part is that it's all shrouded in secrecy. I'm sure I could consult an attorney and have him point out the specific sections of law, and explain how that means parts stores aren't allowed to diagnose my alternator. But that information should be freely and easily accessible to California residents, and it's not.

But all that being said, yeah, it's just as well that I have my own code scanner, and have learned how to do my own diagnostics.
bluey:
I suspect the best test of a car battery is failure to crank. The other vehicle systems are pretty reliable. Charging circuit has a warning light on dash if its not working. So when starting is hard, Just swap out the battery.

Design life of a battery is reflected in the warranty. An Exide rep years ago said 18months.My experience is similar to earlier poster - 4 to 7 years. I have had as many failures in cool weather as hot weather. Seems that a marginal battery can muster some capacity with attempted cranking maybe related to battery warming.

The long version explains why all battery testers are fallible.
https://batteryuniversity.com/learn/article/how_to_measure_internal_resistance
SilverSolder:

--- Quote from: bluey on March 03, 2020, 08:48:20 pm ---I suspect the best test of a car battery is failure to crank. The other vehicle systems are pretty reliable. Charging circuit has a warning light on dash if its not working. So when starting is hard, Just swap out the battery.

Design life of a battery is reflected in the warranty. An Exide rep years ago said 18months.My experience is similar to earlier poster - 4 to 7 years. I have had as many failures in cool weather as hot weather. Seems that a marginal battery can muster some capacity with attempted cranking maybe related to battery warming.

The long version explains why all battery testers are fallible.
https://batteryuniversity.com/learn/article/how_to_measure_internal_resistance

--- End quote ---

That approach can get expensive real fast, because a common failure mode of a starter motor is worn bearings which cause it to draw much more current (while still having trouble starting the engine). 

What you can do, is measure the current drawn by the starter, this easily lets you decide if it is the battery or the starter that is shot.
tautech:

--- Quote from: SilverSolder on March 03, 2020, 10:29:52 pm ---That approach can get expensive real fast, because a common failure mode of a starter motor is worn bearings which cause it to draw much more current (while still having trouble starting the engine). 

--- End quote ---
Not IME.
Every starter is different, those that use a geared reduction give little trouble in that they don't have to provide lots of torque whereas a direct drive starter is a completely different animal entirely.
Direct drive starters only spin relatively slow so mostly use bushes instead of bearings but the currents they draw are much higher which is both harder on brushes and batteries requiring higher CCA rated batteries.
Brush wear in these can be a ongoing issue too, not only of the brush replacement but more frequently servicing to address the conductive carbon contamination inside the brush housing that can add significantly to current draw.

Bushes also require occasional lubrication however that's also done when carbon contamination is addressed.
The average automotive starter doesn't generally experience any of these issues unlike industrial engines that might do several 10's of 1000's of hours and be in service for decades.
YMMV
Navigation
Message Index
Next page
Previous page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod