Car battery tests are of no value - Page 1
Forum section: electronics / general

author: GreggD
author_rank: Regular Contributor
timestamp: July 20, 2017, 03:04:48 pm
content: My neighbor had trouble starting her car yesterday. Took it to Autozone (store) for testing.They load tested the battery and said it was fine, must be a problem with the starter.Three hours later the battery was dead. You know, click-click-click.There was no load left on just a 7 year old battery and they fail suddenly.

author: rstofer
author_rank: Super Contributor
timestamp: July 20, 2017, 03:10:24 pm
content: 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.

author: BradC
author_rank: Super Contributor
timestamp: July 20, 2017, 03:35:47 pm
content: I wouldn't say they have no value. Simply the test you used was not suited to showing up the failure mode you have. Generally a high current load test will weed out most failures in a lead acid starting battery. It sounds like yours has high internal discharge.

author: rustybronco
author_rank: Contributor
timestamp: July 20, 2017, 03:48:47 pm
content: It all will depend on the machine used and the operator of it.

author: ConKbot
author_rank: Super Contributor
timestamp: July 20, 2017, 04:24:25 pm
content: Quote from: rustybronco on July 20, 2017, 03:48:47 pm+1 to that. I've had an alternator tested at autozone after the car was giving symptoms that are alternator related. (Brake light and battery light, weird quirk in the older sentras) and the trash computerized tester gave it a pass in 5 seconds. Took it to advance auto parts, they put it on a tester that had meters and required the operator to know what was going on. 20 seconds after it was turned on, the regulator warmed up, voltage shot up to 20V, bad regulator confirmed.That being said, a battery test is usually charging the battery, and put a cranking load on it and see if it can deliver the cranking amps needed. Won't identify one not holding a charge.

author: Halcyon
author_rank: Unknown
timestamp: July 21, 2017, 01:13:28 am
content: Quote from: GreggD on July 20, 2017, 03:04:48 pm"Just" a 7 year old battery? Your neighbour is getting pretty decent mileage on a battery that old. A car battery over 5 years old is getting to the point where it will need replacement (depending on how it's been treated and environmental factors).I suspect with many modern cars these days that have that automatic start/stop "feature" (where the engine cuts out when stopped), batteries probably won't last even that long. I personally disable that stupid feature. It saves next to no money on petrol, reduces emissions by 'bugger-all' and just places extra stress on the battery and starter motor.

author: deflicted
author_rank: Unknown
timestamp: July 21, 2017, 01:36:40 am
content: Quote from: ConKbot on July 20, 2017, 04:24:25 pmHere 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.

author: joeqsmith
author_rank: Super Contributor
timestamp: July 21, 2017, 01:55:21 am
content: Quote from: rstofer on July 20, 2017, 03:10:24 pmFunny. I can think of only one of our batteries that failed in the summer. All the rest in the cold winter.

author: rdl
author_rank: Super Contributor
timestamp: July 21, 2017, 03:06:38 am
content: Quote from: deflicted on July 21, 2017, 01:36:40 amI'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).

author: John B
author_rank: Frequent Contributor
timestamp: July 21, 2017, 04:09:08 am
content: Every time Ive read the word "car" and "california" together, its always in a negative context.On the topic though, Ive found you get what you pay for when it comes to inspections. Thorough inspections take time, and technician hourly rates aren't going to be cheap. A similar issue is cheap and fast suspension checks. Cars with shot bushings, shot ball joints, shot tie rods = passed test, no wukkas.

author: tautech
author_rank: Super Contributor
timestamp: July 21, 2017, 04:16:19 am
content: Quote from: joeqsmith on July 21, 2017, 01:55:21 amYou 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.

author: deflicted
author_rank: Unknown
timestamp: July 21, 2017, 04:35:59 am
content: Quote from: rdl on July 21, 2017, 03:06:38 amI 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 whoreallykilled 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.

author: bluey
author_rank: Regular Contributor
timestamp: March 03, 2020, 08:48:20 pm
content: 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

author: SilverSolder
author_rank: Super Contributor
timestamp: March 03, 2020, 10:29:52 pm
content: Quote from: bluey on March 03, 2020, 08:48:20 pmThat 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.

author: tautech
author_rank: Super Contributor
timestamp: March 03, 2020, 11:34:59 pm
content: Quote from: SilverSolder on March 03, 2020, 10:29:52 pmNot 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

author: chickadee
author_rank: Contributor
timestamp: March 03, 2020, 11:48:41 pm
content: I keep cars in multiple states, one of them is in Phoenix AZ. That car needs a battery twice as often as the one that is in a rather cold midwest state. Cold weather definitely serves to reduce output, but doesn't necessarily seem to induce failure - The output comes back up with temperature. In phoenix, when that battery is dead, it's dead! And it's like every 2 years!!! Guarantee you I'll have to replace it again soon and I just put one in it summer 2018.

author: maginnovision
author_rank: Super Contributor
timestamp: March 04, 2020, 12:00:49 am
content: In Lake Havasu I don't have the same experience chickadee. Here in southern california the only time I have seen a car battery last <5 years is people using the battery without vehicle running, not using it enough(sleep current eventually kills it), or leaving things on while car is parked. I have one now for a car that sat for 3 months and it was dead. I brought it back over a week and back to service it went. Then the driver left the interior lights on over a weekend and nothing is bringing that battery back now.

author: SilverSolder
author_rank: Super Contributor
timestamp: March 04, 2020, 12:09:33 am
content: Quote from: tautech on March 03, 2020, 11:34:59 pmI guess I'm revealing a tendency to keep cars a REALLY long time!The excessive current issue has happened to me with several different cars, most recently a 1990 Mazda MX5. Fixed with a $20 starter from the auto wreckers!I guess the point is - Don't automatically condemn the battery if the car doesn't seem to crank properly, there is a significant chance that it is the battery, but sometimes it isn't...

author: tautech
author_rank: Super Contributor
timestamp: March 04, 2020, 12:47:31 am
content: Quote from: SilverSolder on March 04, 2020, 12:09:33 amPrecisely !I have machinery up to 50 yrs old that starters only require infrequent servicing and the only starter replaced was a direct drive one in a car that had a dicky ignition switch that occasionally stuck ON and my daughter didn't know and borrowed the car and demolished the starter ! Trip to the wreckers yard for another one.......Luckily machinery starters are easier to remove than automotive ones.

author: chickadee
author_rank: Contributor
timestamp: March 04, 2020, 02:12:32 am
content: Quote from: maginnovision on March 04, 2020, 12:00:49 amIn 10 years I still haven't made it out that way! Camping all over prescott and grand canyon, love sedona, but sooner or later I will make it out that way!It looks like the climate there is similar to PHX, so I would hypothesize that the car's underhood temperatures in PHX are higher? The area has really become a sea of pavement, I only drive older EU cars and the one I have there is a twin turbo so the underhood temps are definitely "WAY UP THERE". The battery has never died when the car was sitting and the car isn't left alone for more than a couple months at a time. I've spoken with colleagues and they seem to have similar experiences, maybe this is just a PHX thing? Or rather, a "living in a sea of 150 degree pavement" thing? I remember the last time the battery died so well, because it was the same week that it was so hot that they were grounding the CRJ aircraft at PHX due to air densityBy the way, right now, thinking of that hot pavement is making me crave dutch bros ice coffee... I have 2 fully loaded punch cards already in my wallet so I don't forget them like I did last time