Please educate me on car battery testing

[cout]

I have read through old forum posts on car battery testers and I've learned a lot, but I'm still confused.

Here's what I've gleaned: there are many different kinds of testers (carbon pile, DC load, AC conductance, EIS). Each has different advantages/disadvantages (which I won't recount here), and forum members have a lot of strong opinions on which one is "best". There are many different brands recommended over the years (Midtronics, Solar/CA Clore, Ancel, Schumacher, to name a few). Some of them have basic grey/black LCD displays, some have backlit displays, and some have fancy color LCD pixel grids like a mobile phone. And some people get upset that anyone buys a tester at all, instead advocating for cranking the car while using a multimeter (presumably the multimeter is built from scrap parts to save extra money).

First question: when I'm looking at a particular battery tester, how can I know what kind it is? Most of the listings don't explicitly say. For example, the Solar BA6 and BA9. They are small, so clearly not carbon pile. They don't say anything about testing a partially discharged battery, but they do read out CCA. Are they conductance testers? Another example, the Solar 100 and the Schumacher BT100. These still look smaller than a carbon pile tester. Are they DC load testers?

Second question: what's with all the different battery standards acronyms? A few I've seen: CCA, CA, DIN, IEC, EN, MCA, JIS, SAE, GB, and BCI. Do these mean anything important or are they just there to puff up the listing?

Third question: I'm a data guy. I love seeing data, so the testers that show the voltage over time appeal to me (they call it a "waveform" but the graph doesn't look much like a wave to me). Can these testers do everything that the more basic testers can do? (comparing e.g. the Ancel BA301 to the BA101, both of which I've seen recommended). I'd love to spring for a Midtronics but I'm a believer in getting something cheap and finding its limitations, so I'm a more informed buyer when I finally shop for the more expensive model. But is this "waveform" display useful? What would you use it for?

I have a lot more questions but I'll stop there for now.

 

[dnschmidt]

The carbon pile ones worked for 50 years and were industry standard sort of like Midtronics are now. The basic principle of loading the battery and watching the voltage drop is foolproof. The ones that measure the internal resistance of the battery like the Midtronics seem to work well but there are a lot of electronics that can **** up between the positive and negative leads.

 

[oldmachinenut]

I have a Sun VAT-40 in my shop. It is a carbon pile type load, simple and reliable like it’s owner.

 

[theoldwizard1]

The most important thing about testing a battery is making sure it is fully charged ! If you ssu

 

[Wrench97]

If the battery is in the car you test it under load with a voltmeter by cranking the starter to apply the load.

I would charge the battery before testing with any tester.

You can get close by just using a voltmeter a healthy 12v battery should read around 12.6 v if it's disconnected from the car reads 12.6v and drops over time it's a bad battery.

Electronic testers with printers attached are sales devices for use in shops.

The Schumacher BT100 is a decent low buck tester once you learn how to use it.

​

 

[richfinn]

I've tested a lot of car batteries over the past 20 years (we use a midtronics with a current clamp for starter load/alternator/current absorption testing/drain), we also see a lot of Enhanced flooded and AGM batteries where you need this type of digital tester. And the procedure is guided and walks you through the full test procedure.

We use these because they are fast and you can fully test a discharged battery at the roadside within 10 minutes with one neat package

It depends on how your going to use the tester, DIY or in a Pro workshop.

All the different battery spec codes you listed are a thing and you need to enter the correct info and temperature into the tester for accuracy.

we replaced our old load testers about 18 years ago with an earlier version of midtronics
then again about 8 years ago with a newer model, so they aren't a buy once kind of tool and the leads/clamps are expensive to replace when they wear out.



If you are DIY/or wanting a tool for your own personal use in the shop take a look at picoscope (they have a dedicated battery test function) and might be a better value purchase if you do any other diagnostic work on vehicles.

Eric O did a quick video

 

[2ndGearRubber]

I've tested a lot of car batteries over the past 20 years (we use a midtronics with a current clamp for starter load/alternator/current absorption testing/drain), we also see a lot of Enhanced flooded and AGM batteries where you need this type of digital tester. And the procedure is guided and walks you through the full test procedure.

We use these because they are fast and you can fully test a discharged battery at the roadside within 10 minutes with one neat package

It depends on how your going to use the tester, DIY or in a Pro workshop.

All the different battery spec codes you listed are a thing and you need to enter the correct info and temperature into the tester for accuracy.

we replaced our old load testers about 18 years ago with an earlier version of midtronics
then again about 8 years ago with a newer model, so they aren't a buy once kind of tool and the leads/clamps are expensive to replace when they wear out.



If you are DIY/or wanting a tool for your own personal use in the shop take a look at picoscope (they have a dedicated battery test function) and might be a better value purchase if you do any other diagnostic work on vehicles.

Eric O did a quick video

Pico automotive software only works with automotive scopes. You're starting around 850 for a 2 channel.

That's if you want the hand holding, any scope can use voltage or current probes to do the same test. You just go without the nice spec sheet pico provides. IIRC someone on YouTube has instructions to trick the pico automotive software into working on a regular base model. I have an automotive scope, so idk if that works.


IMO the fastest battery test is your ear. You can hear dying batteries, cranking slow as hell and barely getting the engine running. Walk through a large parking lot, find a car from 2003. And listen to it start. Voltage drop the cables, if the battery can even start it 3 times in a row LOL, and you know the only issue is the battery.

If a battery fails the little capacitance testers like midtronics, it's bad. If it passes..... it's still debatable. I like to see a battery hold the low beams on with the ignition on, for 1-2 minutes, THEN pass the battery test. Plenty will be good on the fancy testers, but clickclickclick after 30 seconds with the headlights on.

You can also use a midtronics style capacitance tester in intervals, like every 10 minutes, and watch the surface charge from the car driving to the shop erode. It's not common to see batteries below 12v with the key on, and still manage to start. It's not uncommon to se them at 12.2 at rest with no loads. Just the reality of the general public and daily drivers. 12.6 only exists in test books or hot off the charger.

I personally do not charge batteries. I replace them. I will only charge them to maintain them during testing of electrical systems i cant leave the car running for the whole time. That's an entirely different discussion.

 

[charbar]

Your multimeter, some deductive reasoning and a little common sense is going to be more accurate at determining your battery's state of health than a handheld digital battery tester. But if you are a 'visual data' type of guy then Midtronics is who you want to look at. And then when you are scratching your head wondering why your battery acts like it is shot but the tester says it's ok just remember to go with your gut feeling and replace the battery, and then cuss about how you could have been drinking a beer much earlier if it wasn't for that damn misleading tester, and also how much more beer money you would have if you would have never bought the worthless thing to start with. See where I'm going with this? I've seen it happen to techs who put too much faith into a piece of equipment that common sense will tell you has no way of accurately testing a battery.

Last time I used a battery tester has been roughly 12 years ago when I was still at the dealer and GM required it to warranty batteries. I run my own shop now and haven't and will not waste the shop's money on a battery tester.

A big ole carbon pile tester is about the only tester that I feel can give you 'real world' results and not some b.s. number and fun graph a computer pumped out......

That's my $.01......not the full two cents because I have more I could add but I don't need to get that riled up before I go to bed

 

[mervyn]

Used one of these when I worked at a parts house about 30 years ago. Customers loved it as it was simple and easy to see if the battery was good or bad. How accurate it was is anybodys guess lol

 

[cout]

If you are DIY/or wanting a tool for your own personal use in the shop take a look at picoscope (they have a dedicated battery test function) and might be a better value purchase if you do any other diagnostic work on vehicles.

Eric O did a quick video

I have a DSO Quad that I've used a handful of times. Someone wrote a protocol analyzer for it, but I've never tried it, and it requires uploading new firmware. Sounds like the picoscope does that and more out of the box. Is there a particular model you'd recommend?

 

[MBfreak]

No need to turn this into rocket science.
Get hold of a DVM that can capture the lowest voltage and store/display it.
Clip it on the battery poles, disconnect ignition and crank 10 seconds.
A voltage reading below 9,5 V , charge the battery fully and retest. Still below 9,5?
Replace battery.

Ola

 

[richfinn]

I have a DSO Quad that I've used a handful of times. Someone wrote a protocol analyzer for it, but I've never tried it, and it requires uploading new firmware. Sounds like the picoscope does that and more out of the box. Is there a particular model you'd recommend?

Really there are two versions of the automotive picoscope, a 2 or 4 channel
(An 8 channel exists but I've never seen one)

Newer versions use BNC+ connections which takes some frustration out of setting up probes (but you need to buy specific pico accessories to use the + function)

But all Picos can all be used using older regular BNC probes if you already have them

The pico software is free to download, and you can buy a basic automotive 2 channel without any accessories reasonably cheap at around £600-700

 

[richfinn]

No need to turn this into rocket science.
Get hold of a DVM that can capture the lowest voltage and store/display it.
Clip it on the battery poles, disconnect ignition and crank 10 seconds.
A voltage reading below 9,5 V , charge the battery fully and retest. Still below 9,5?
Replace battery.

Ola

Time consuming though fully recharging batteries, midtronics will test a full system including discharged batteries in 10 minutes.

If you understand what it does and the pitfalls of the different elements of the test procedure it's a lot more profitable and efficient when your dealing with 5 or 6 battery jobs per day

This is why most manufacturers specify midtronics as dealership equipment (it also keeps a record of test performed for warranty claims.)

It's definately not aimed at DIY

Your quite right though, you can test a battery with a volt meter/dc current clamp/charger/hydrometer and use the starter as a load.

Nobody does it in a pro workshop environment anymore as it's not possible to charge it out to customers as they can buy a new battery for less than the labour would cost!!!

 

[bwringer]

It's definately not aimed at DIY

Your quite right though, you can test a battery with a volt meter/dc current clamp/charger/hydrometer and use the starter as a load.

Nobody does it in a pro workshop environment anymore as it's not possible to charge it out to customers as they can buy a new battery for less than the labour would cost!!!

Yep, for a home gamer there's really nothing worthwhile you can get from fancier testers. If you're a busy pro shop dealing with warranty claims, then maybe you need the printout or whatever to convince the manufacturer.

They key is to think about this from a cold-blooded economic perspective.

Despite what many people seem to think, car batteries are not precious heirlooms; they are consumables with a constantly declining value and an average reliable lifetime of maybe four to five years. A fancy $200 AGM amortized over 60 months comes out to a measly $3.33 per month; almost nothing compared to the cost of gas, tires, and other maintenance.

Yes, there are outliers, and it's great that the battery in your ol' blue truck is on year 10... I'm not sending my wife to work with an elderly battery in her car just to save that three bucks for a few more months.

The other thing to remember is the cost of a failure, in money, time, inconvenience, and even safety. One failure at midnight when it's below zero more than wipes out any possible benefit from years of "stretching" batteries a few more months.

I always replace batteries at MY convenience (when I have daylight, time, warmth, and perhaps a sale...) well before the curve gets steep. There's also the cost of other failures; nursing a dying battery strains the charging system, and can cause an expensive alternator to fail prematurely.

If the battery costs, say, $150 or $200 all in, and you're already on year #3 or 4, it's not worth spending more than a few minutes trying to salvage a consumable with that little value left. You do, of course, need to properly diagnose with a voltmeter to make sure you don't also have a charging issue.

Likewise, I don't see any value at all in investing in some sort of fancy-schmancy battery analyzer. Put that money toward your next battery.

All that said: if you're just curious, you want to spend the money on a nice tool, and you just enjoy "scientific" tools and data, then by all means feel free to get fancy and analyze batteries to your heart's content. This is GJ, after all, where the answer to "Which tool?" is always "Yes!"

 

[Buckaroo5]

I have had an earlier version of this inexpensive Clore Solar tester for many years. It is based on capacitance (like the Midtronics) and gives you a current CCA capacity readout and a pass/fail indication vs the label CCA (I think the pass/fail limit that they apply is 80% of label?). It is easy & quick plus you don't have to fully charge the battery like the old load based testers. It also test starter and charger. I'm a data guy too so I test the batteries as part of normal maintenance and document the CCA as the battery degrades over time.

SOLAR BA9 Digital Battery & System Tester - Clore Automotive

The BA9 is the newest addition to the SOLAR Battery Tester family. The BA9 is a pocket-sized battery and system tester for 12 Volt batteries, featuring an

cloreautomotive.com

This is a great article on the various types of battery testing available and their advantages and disadvantages.....

A Battery of Tests | MOTOR

www.motor.com

 

[MBfreak]

bwringer wrote
They key is to think about this from a cold-blooded economic perspective.

Wouldn´t that take away 98% of GJ posts?

Ola

 

[joel63]

Time consuming though fully recharging batteries, midtronics will test a full system including discharged batteries in 10 minutes.

If you understand what it does and the pitfalls of the different elements of the test procedure it's a lot more profitable and efficient when your dealing with 5 or 6 battery jobs per day

This is why most manufacturers specify midtronics as dealership equipment (it also keeps a record of test performed for warranty claims.)

It's definately not aimed at DIY

Your quite right though, you can test a battery with a volt meter/dc current clamp/charger/hydrometer and use the starter as a load.

Nobody does it in a pro workshop environment anymore as it's not possible to charge it out to customers as they can buy a new battery for less than the labour would cost!!!

Does anyone use a hydrometer anymore?

 

[charbar]

Does anyone use a hydrometer anymore?

If I still have one it has to be buried under 200 pounds of **** in a junk drawer somewhere. A quick glance at my battery rack and there isn't a single battery on it that has caps to even test that way

 

[4xdog]

Does anyone use a hydrometer anymore?

I do. But I'm not a pro -- just a guy who's spent his life in industrial chemistry.

 

[joel63]

Yep, for a home gamer there's really nothing worthwhile you can get from fancier testers. If you're a busy pro shop dealing with warranty claims, then maybe you need the printout or whatever to convince the manufacturer.

They key is to think about this from a cold-blooded economic perspective.

Despite what many people seem to think, car batteries are not precious heirlooms; they are consumables with a constantly declining value and an average reliable lifetime of maybe four to five years. A fancy $200 AGM amortized over 60 months comes out to a measly $3.33 per month; almost nothing compared to the cost of gas, tires, and other maintenance.

Yes, there are outliers, and it's great that the battery in your ol' blue truck is on year 10... I'm not sending my wife to work with an elderly battery in her car just to save that three bucks for a few more months.

The other thing to remember is the cost of a failure, in money, time, inconvenience, and even safety. One failure at midnight when it's below zero more than wipes out any possible benefit from years of "stretching" batteries a few more months.

I always replace batteries at MY convenience (when I have daylight, time, warmth, and perhaps a sale...) well before the curve gets steep. There's also the cost of other failures; nursing a dying battery strains the charging system, and can cause an expensive alternator to fail prematurely.

If the battery costs, say, $150 or $200 all in, and you're already on year #3 or 4, it's not worth spending more than a few minutes trying to salvage a consumable with that little value left. You do, of course, need to properly diagnose with a voltmeter to make sure you don't also have a charging issue.

Likewise, I don't see any value at all in investing in some sort of fancy-schmancy battery analyzer. Put that money toward your next battery.

All that said: if you're just curious, you want to spend the money on a nice tool, and you just enjoy "scientific" tools and data, then by all means feel free to get fancy and analyze batteries to your heart's content. This is GJ, after all, where the answer to "Which tool?" is always "Yes!"

A whole lot of truth here.
Well done!

 

[rlitman]

...If a battery fails the little capacitance testers like midtronics, it's bad. If it passes..... it's still debatable. I like to see a battery hold the low beams on with the ignition on, for 1-2 minutes, THEN pass the battery test. Plenty will be good on the fancy testers, but clickclickclick after 30 seconds with the headlights on.

You can also use a midtronics style capacitance tester in intervals, ...

First off, Midtronics and the like do not test capacitance. It's a shame you don't understand how they work or what they do, but they actually draw higher currents than carbon testers, while doing less damage to your batteries.

Second, testing a battery after the headlights are on is woefully out of date advice, and tells you little about the readiness of a battery to start a vehicle. Modern cars are getting smaller and smaller batteries every year, for cost savings, to cut weight for better fuel economy, to save space under the hood and to increase battery sales at dealerships. Carbon and drawdown testing of smaller batteries goes a long way to shortening their lifetimes, particularly when modern batteries are optimized for high CCA but low reserve capacity.

Does anyone use a hydrometer anymore?

A hydrometer tells you nothing for certain about the condition of a battery other than its state of charge. You can get that more safely from a voltmeter. They're also pretty finicky about temperature. I own and use ATC refractometers in places where hydrometers used to be appreciated (for automotive purposes, I use a refractometer on antifreeze).

 

[dcg9381]

Does anyone use a hydrometer anymore?

50% of my vehicle batteries are AGM.

 

[richfinn]

Does anyone use a hydrometer anymore?

Not really, I was using it to make a point

"There's always another way to skin a cat"

Modern diagnostic tools are basically like power tools, they speed up the work and make it more efficient in a pro environment.

Sure you could replace a transmission using basic hand tools on jackstands.

But if you want to speed things along you use a lift and cordless/air tools.

 

[richfinn]

Yep, for a home gamer there's really nothing worthwhile you can get from fancier testers. If you're a busy pro shop dealing with warranty claims, then maybe you need the printout or whatever to convince the manufacturer.

They key is to think about this from a cold-blooded economic perspective.

Despite what many people seem to think, car batteries are not precious heirlooms; they are consumables with a constantly declining value and an average reliable lifetime of maybe four to five years. A fancy $200 AGM amortized over 60 months comes out to a measly $3.33 per month; almost nothing compared to the cost of gas, tires, and other maintenance.

Yes, there are outliers, and it's great that the battery in your ol' blue truck is on year 10... I'm not sending my wife to work with an elderly battery in her car just to save that three bucks for a few more months.

The other thing to remember is the cost of a failure, in money, time, inconvenience, and even safety. One failure at midnight when it's below zero more than wipes out any possible benefit from years of "stretching" batteries a few more months.

I always replace batteries at MY convenience (when I have daylight, time, warmth, and perhaps a sale...) well before the curve gets steep. There's also the cost of other failures; nursing a dying battery strains the charging system, and can cause an expensive alternator to fail prematurely.

If the battery costs, say, $150 or $200 all in, and you're already on year #3 or 4, it's not worth spending more than a few minutes trying to salvage a consumable with that little value left. You do, of course, need to properly diagnose with a voltmeter to make sure you don't also have a charging issue.

Likewise, I don't see any value at all in investing in some sort of fancy-schmancy battery analyzer. Put that money toward your next battery.

All that said: if you're just curious, you want to spend the money on a nice tool, and you just enjoy "scientific" tools and data, then by all means feel free to get fancy and analyze batteries to your heart's content. This is GJ, after all, where the answer to "Which tool?" is always "Yes!"

Thats why I think the picoscope has merit for a DIYer, if you like data and you need a battery tester it can do all that.

The real advantage is it can be used for so many more types of automotive testing on any type of vehicle and it never goes out of date!!!

 

[zmotorsports]

Used one of these when I worked at a parts house about 30 years ago. Customers loved it as it was simple and easy to see if the battery was good or bad. How accurate it was is anybodys guess lol

Still have that exact one in my cupboard. I too used one back in the 80's when I was a parts peddler in several of the auto parts stores I worked in. It would work well for immediate charge but not much else. Basically the same thing as a VOM with a battery in the car and cranking.

I don't use and haven't for many years and now use either my Midtronics or my carbon pile tester but can't seem to get rid of tools. I also use my hydrometer to determine state of charge as well as a VOM meter for comparisons. The min/max feature on many VOM's is a nice option while cranking as well as once running to determine charge voltage.

 

[2ndGearRubber]

First off, Midtronics and the like do not test capacitance. It's a shame you don't understand how they work or what they do, but they actually draw higher currents than carbon testers, while doing less damage to your batteries.

Second, testing a battery after the headlights are on is woefully out of date advice, and tells you little about the readiness of a battery to start a vehicle. Modern cars are getting smaller and smaller batteries every year, for cost savings, to cut weight for better fuel economy, to save space under the hood and to increase battery sales at dealerships. Carbon and drawdown testing of smaller batteries goes a long way to shortening their lifetimes, particularly when modern batteries are optimized for high CCA but low reserve capacity.


A hydrometer tells you nothing for certain about the condition of a battery other than its state of charge. You can get that more safely from a voltmeter. They're also pretty finicky about temperature. I own and use ATC refractometers in places where hydrometers used to be appreciated (for automotive purposes, I use a refractometer on antifreeze).

Conductance, my mistake.

I use a pico and the starter if I want a real battery test. Freebie no diag gets the dumb type with the tiny printer built in. There's no real current flow. EXP800 is what we use. Look at the little baby clamps and cables. Iirc it sends a signal through the battery and measures the drop in signal strength?

I want to beat the battery as hard as possible and confirm it will not fail when someone leaves the lights on or a door cracked. I want it to fail, now, rather than in 6 months when the customer is in a snow storm. Ideally we would just replace based on an interval, like one should do with filters instead of constantly ripping the air box apart.


IMO if your battery can't keep the low beams on for 60 seconds and still pass a starting test for minimum voltage, it's a ************* battery and needs replaced. Two low beams at 12v is like 9 amps.

I would also disagree with batteries getting smaller, they're staying the same or getting massive agm batteries the size of a cinder block. Stop start vehicles often have 2, a cinder block and a baby lawn and garden size. The battery in a town and country has probably increased in size by 20% from 2005, and may have an additional baby battery.

 

[RalphInCA]

Your multimeter, some deductive reasoning and a little common sense is going to be more accurate at determining your battery's state of health than a handheld digital battery tester. But if you are a 'visual data' type of guy then Midtronics is who you want to look at. And then when you are scratching your head wondering why your battery acts like it is shot but the tester says it's ok just remember to go with your gut feeling and replace the battery, and then cuss about how you could have been drinking a beer much earlier if it wasn't for that damn misleading tester, and also how much more beer money you would have if you would have never bought the worthless thing to start with. See where I'm going with this? I've seen it happen to techs who put too much faith into a piece of equipment that common sense will tell you has no way of accurately testing a battery.

Last time I used a battery tester has been roughly 12 years ago when I was still at the dealer and GM required it to warranty batteries. I run my own shop now and haven't and will not waste the shop's money on a battery tester.

A big ole carbon pile tester is about the only tester that I feel can give you 'real world' results and not some b.s. number and fun graph a computer pumped out......

That's my $.01......not the full two cents because I have more I could add but I don't need to get that riled up before I go to bed

I vote for Charbar as the smartest man on the room.

 

[engineer2]

I like that more batteries have a date sticker on them. When it gets to be 4 years old, I keep an eye on it.
The most vulnerable driver gets the newest battery. In my case, it's the kid who's at school 400 miles away. I switched the oldest battery to my car because it's no problem to get a jump and drive to the parts store.
Maintenance is important. Clean, tight terminals, water levels topped up (where possible).

My cheap conductance tester will estimate the available CCA, but it can be fooled by a partially discharged battery.
If in doubt, I use my Bear engine analyzer with the battery load tester. It can diagnose a partially discharged battery. Old tech, but it still tells you good, marginal or replace battery.

When Bear developed it, they got pallets of used batteries from local stores. They recorded discharge curves (voltage vs time) on hundreds of batteries and developed an algorithm to diagnose batteries. Interestingly they found quite a few batteries that had been replaced were simply low on charge.

 

[2ndGearRubber]

^ failed is failed in my book, whether low on charge or a bad cell. There's no interval to charge the thing, the charging system should be maintaining the battery at a suitable level. Yes, I'm aware modern charging strategies choose limited alternator engagement over max battery life.

IME when a battery fails to start a vehicle, it can often be brought back to life with charging. Only to die again a few months later. I don't mess around anymore, if the battery won't start the car, replace it. Assuming the cables and whatnot are good obviouly.

 

[theoldwizard1]

To get an accurate test on a lead acid battery, it needs to be at 100% State of Charge. Best way to do this is disconnect the battery ground and charge for at least 12 hours. Let rest for about 30 minutes. The no load voltage should be close to 13.2V. if you are below 13V, the battery is on its way out.

 

[bwringer]

^ failed is failed in my book, whether low on charge or a bad cell. There's no interval to charge the thing, the charging system should be maintaining the battery at a suitable level. Yes, I'm aware modern charging strategies choose limited alternator engagement over max battery life.

IME when a battery fails to start a vehicle, it can often be brought back to life with charging. Only to die again a few months later. I don't mess around anymore, if the battery won't start the car, replace it. Assuming the cables and whatnot are good obviouly.

Yeah, that charging management thing kinda surprised me the first time I encountered it, but it makes sense. Why would it hurt battery life?


Anyway, yup, not worth farting around with charging a battery just to get a little further down the road (unless it's the only way to get to a place that sells batteries). Life is brutal, and at the first sign of weakness batteries must be exiled to the outer darkness and replaced.

And also yep, carefully check the cables at BOTH ends while you're at it.

How many monster movies feature a scene where someone runs to a car to get away from the zombies or werewolf or whatever, and the battery dies before it starts, with the creature or aien pounding on the window? Not worth risking axe murder if you ask me, but lots of people do.

 

[Garcky]

I live in Minnesota. Gets down to -20 degrees F or lower here several times a year. So, I give batteries 3 years and replace them. So far, my cars have started every time I've needed them. I'm not really into going out to go somewhere and finding a dead battery. Nope. Some folks here get more years than that from their batteries. I don't care. I just replace them after 3 winters.

 

[joel63]

To get an accurate test on a lead acid battery, it needs to be at 100% State of Charge. Best way to do this is disconnect the battery ground and charge for at least 12 hours. Let rest for about 30 minutes. The no load voltage should be close to 13.2V. if you are below 13V, the battery is on its way out.

Charge at what rate for 12 hours ?

 

[joel63]

I live in Minnesota. Gets down to -20 degrees F or lower here several times a year. So, I give batteries 3 years and replace them. So far, my cars have started every time I've needed them. I'm not really into going out to go somewhere and finding a dead battery. Nope. Some folks here get more years than that from their batteries. I don't care. I just replace them after 3 winters.

Very difficult to argue with this proactive approach.

 

[theoldwizard1]

I live in Minnesota. Gets down to -20 degrees F or lower here several times a year. So, I give batteries 3 years and replace them.

I live in SE MI, not nearly as cold as you, but it does go below 0F sometimes. I have had starting batteries last over 10 years.

I will gladly keep the extra money in my pocket.

 

[American Locomotive]

First off, Midtronics and the like do not test capacitance. It's a shame you don't understand how they work or what they do, but they actually draw higher currents than carbon testers, while doing less damage to your batteries.

Conductance testers draw very little real current from a battery. They measure battery characteristics by applying an AC signal and analyzing how the battery responds to that signal.

Second, testing a battery after the headlights are on is woefully out of date advice, and tells you little about the readiness of a battery to start a vehicle. Modern cars are getting smaller and smaller batteries every year, for cost savings, to cut weight for better fuel economy, to save space under the hood and to increase battery sales at dealerships. Carbon and drawdown testing of smaller batteries goes a long way to shortening their lifetimes, particularly when modern batteries are optimized for high CCA but low reserve capacity.

Why would leaving the headlights on for a minute damage the battery? Why would using a carbon pile tester damage the battery? It's not like you're leaving your carbon pile tester on for 5 minutes straight at 300A.

 

[charbar]

I live in SE MI, not nearly as cold as you, but it does go below 0F sometimes. I have had starting batteries last over 10 years.

I will gladly keep the extra money in my pocket.

Over 10 years is impressive. Last week a customer brought a pair of group 31s out of his Deere tractor that finally gave up......the date scratched in them was almost exactly 10 years to the date. I about fell over. If I see 7-8 years out of a battery around here I am impressed, 10 years is an act of God.

 

[rlitman]

Conductance testers draw very little real current from a battery. They measure battery characteristics by applying an AC signal and analyzing how the battery responds to that signal.

Why would leaving the headlights on for a minute damage the battery? Why would using a carbon pile tester damage the battery? It's not like you're leaving your carbon pile tester on for 5 minutes straight at 300A.

They don't "apply an AC signal". They shunt the battery switched over a sweep of frequency modulated pulses (not alternating though, since the battery itself is DC, duh). ENERGY consumed is based on the area under the curve, which is very small (a thermal necessity), since the pulses are of such short duration. But the CURRENT applied is necessarily very high (think dead short). There's a reason these testers depend on "Kelvin" clamps (to remove the probe wire's resistance from the equation; "very little current" would not require a Kelvin clamp!). Look at what they're doing on a scope (if you have something fast enough to capture it).

Lead-acid battery longevity depends a lot on how much time is spent at float charge. Every discharge cycle eats away battery life, and the more energy you draw off with each cycle (or test), the more impact your test (or engine start) will have on battery life. How much harm depends a lot on the battery quality, and sure, it might not amount to much, but it's still wasteful and not all that useful a diagnostic. Do this too often, and it will be a self fulfilling prophecy. Particularly when your charger feels the need to equalize after recharging before returning to float.

As for my opinion on conductance/impedance/ESR testers (I've used Midtronics, Alber and HP, among others), I think the biggest issue people have with them is not understanding how to collect or interpret results. You can't just clamp onto a battery, take a reading and really know if it is good or bad without good baseline data about THAT jar's characteristics. And batteries can behave in weird ways, seemingly getting better sometimes, so a single test may miss some prior event when it was misbehaving.

Attached is an example to illustrate. It shows an overlay of the float voltages for 40 individual 12V jars (this amounts to a single cabinet of which I maintain several), each traced in a different color, over the course of one month. I have other charts in the same time series of internal resistances (taken roughly hourly) that only show insignificant changes in resistance over most of the period where you can clearly see the voltage swings in the battery I had warranty replaced. Also not shown is a wider view where I found that same battery took another "excursion" several months before this one and then fully recovered into the pack again.

As for my own car battery, I'll run my test when it's new, and write the date and result on the top. I then check it at least once a year, and see if there are significant changes. And then there's always a jump pack.

 

[2ndGearRubber]

Yeah, that charging management thing kinda surprised me the first time I encountered it, but it makes sense. Why would it hurt battery life?


Anyway, yup, not worth farting around with charging a battery just to get a little further down the road (unless it's the only way to get to a place that sells batteries). Life is brutal, and at the first sign of weakness batteries must be exiled to the outer darkness and replaced.

And also yep, carefully check the cables at BOTH ends while you're at it.

How many monster movies feature a scene where someone runs to a car to get away from the zombies or werewolf or whatever, and the battery dies before it starts, with the creature or aien pounding on the window? Not worth risking axe murder if you ask me, but lots of people do.

You'll find a lot of smart charging systems are designed for absolute bare minimum alternator engagement. Idling the engine the battery may sit at less than 12.6v, negligible charging current. This means the battery isn't being overcharged, which is a plus, but the battery can also be run in conditions of charging maintenance which don't maintain it properly. There isn't enough energy going back into the battery. Add an older already weak battery, and a system set up to essentially undercharge it, and your failure point is easier to hit. Imagine you are sitting and idling at 12.2v, and shut off the car. You're already "undercharged" for a starting the engine or testing via conventional wisdom. Yet this is how most batteries live their lives. So a tenth or two makes a big difference, and if the alternator is prioritizing reduction of parasitic loads vs a tenth of battery voltage.......

FWIW with battery aging estimates (battery registration), current/voltage sensors, etc, things seem to be improving. Downside is electrical demands grow higher every day on modern vehicles. Which taxes the battery even more. Batteries are also made to die within a certain period, so that's another variable.

 

[American Locomotive]

Lead-acid battery longevity depends a lot on how much time is spent at float charge. Every discharge cycle eats away battery life, and the more energy you draw off with each cycle (or test), the more impact your test (or engine start) will have on battery life. How much harm depends a lot on the battery quality, and sure, it might not amount to much, but it's still wasteful and not all that useful a diagnostic. Do this too often, and it will be a self fulfilling prophecy. Particularly when your charger feels the need to

We're talking about running head lights for 1 minute, or doing a 5 second carbon pile load test. Both are equivalent to normal every day usage. It's not abnormal use at all. It's like saying starting your car or listening to music for a few minutes with the engine off is a sell fulfilling prophecy to battery failure. Well yeah....

They don't "apply an AC signal". They shunt the battery switched over a sweep of frequency modulated pulses (not alternating though, since the battery itself is DC, duh). ENERGY consumed is based on the area under the curve, which is very small (a thermal necessity), since the pulses are of such short duration. But the CURRENT applied is necessarily very high (think dead short). There's a reason these testers depend on "Kelvin" clamps (to remove the probe wire's resistance from the equation; "very little current" would not require a Kelvin clamp!). Look at what they're doing on a scope (if you have something fast enough to capture it).

The current is still low as dictated by ohm's law. Look at the cables on a Midtronics conductance tester - there are two wires in each cable, meaning they're tiny. Approximately 22 gauge by eyeball. 5 feet of 22 gauge copper will have a resistance of about 0.08 ohms. V=IR, which means at 12.6v, the absolute maximum current that could possibly flow through those wires is 157 amps.

Proper conductance testers DO pump a small AC current through the battery and calculate the battery's impedance. The gist is that a good battery will develop very little AC voltage across it (low impedance), while a bad battery will develop higher AC voltage (high impedance). I've read about (and personally witnessed) countless cases where those testers say a battery is fine, but the battery won't perform at all in service. There's a competing technology called EIS, which uses similar principals to conductance testing, but requires each specific model of battery to be fully characterized. It's supposed to be really accurate, but if you're testing a mystery battery with its label peeled off - well?

The only true test is a battery load test. Even the conductance/eis battery test companies admit this. The carbon pile doesn't lie. Either the battery can deliver 800 amps, or it can't. Either the battery can supply 15A for 60 minutes, or it can't. No guessing. No uncertainty. It either performs, or it doesn't.

In certain applications (online UPS, grid storage, etc..) it's obviously not practical to use a carbon pile tester (or any other resistive tester) hence the need for these conductance or EIS devices. But for an automotive application, the carbon pile is practical, reliable and fool-proof. Shoot, just pulling the fuel pump relay and letting it crank for 10-15 seconds is probably a good enough test.