Auto Battery Load Tester

[lardy1]

I'm pretty much in the dark here trying to figure out if my girlfriends car needs a battery or a mechanic. Is there a definitive way to test a battery with a cheap analog multi-meter or am I going to need a load tester?

Are the low end ones adequate for occassional home use? I see some digital ones below twenty dollars but I try not to let low cost guide my purchases.

Any advice is truly appreciated. I didn't learn these things as a carpenter or by wheeling steamboats.

 

[Negen]

When fully charged the battery should be slightly above 12 volts but not yet 13. When engine is running the voltage should be over 13.5 volts but not above 14 volts.

Most auto parts stores will load test the battery for you.

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[zendriver]

I’ve got a $20 analog load battery tester from Harbor freight for 10 years now

Seems to get the job done


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[TonyJ]

When fully charged the battery should be slightly above 12 volts but not yet 13. When engine is running the voltage should be over 13.5 volts but not above 14 volts.

Most auto parts stores will load test the battery for you.

Sent from my ONEPLUS A6013 using The Garage Journal mobile app

This voltage also depends on the car and the type of alternator it has. Like for instance my Jaguar has a always changing voltage alternator that changes the charging voltage depending on the load. Riding down the road it can be as high as 15.4 to as low as 11.9. Strange as hell I know but that’s how some cars are.

To the op take the car to a parts store and have them check it. They can load test it while it’s still in the car and it’s usually always free to have done

 

[unslow1]

You don't need a load tester but it's free at the local auto parts stores. If you don't have one near you it can be done even with a Harbor Freight freebie. Basically you attach the meter to the battery and start the car to see how low the voltage drops while cranking. Then you can also test the alternator to see what happens to the voltage at various loads and RPM.

 

[2ndGearRubber]

This voltage also depends on the car and the type of alternator it has. Like for instance my Jaguar has a always changing voltage alternator that changes the charging voltage depending on the load. Riding down the road it can be as high as 15.4 to as low as 11.9. Strange as hell I know but that’s how some cars are.

To the op take the car to a parts store and have them check it. They can load test it while it’s still in the car and it’s usually always free to have done

Glad someone pointed that out. That's true of 20yo cars. As you said, modern stuff is kissing the mid-15 volt charging output.

______________________________________________



A digital load tester via the parts store is one of the only decent DIY options.

At the end of the day, you need a load to be confident in the test results. But the electronic ones will pick up 75% of problems. And all the local shops will be using, is the same midtronics unit the parts store uses. IMO the min/max feature on the meter, under cranking, is probably a better test of the battery than a generic load test.

I almost never test batteries, when I do, I use the Pico. Not DIY friendly.

 

[lardy1]

When the battery is unhooked from the car and charged, the small analog meter shows slightly over 12v. From what I'm reading that's about right. When I install the battery and have her crank the starter it only drops to around eleven. What I'm reading tells me if it's above ten the battery likely isn't my problem.

Ford Edge has a huge problem with the battery creating all kinds of corrosion around the terminals. This particular one got so bad it ruined those jokes that Ford engineers pass off as terminal clamps. We had new terminals (the old type) soldered on and it went well until recently. I've cleaned every connection I can see and tightened everything down. I'm going to just have her use it for short jaunts and I'll test it after each run with the El Cheapo multi-meter.

I really appreciate the folks that have offered their experience and advice. Thank you.

First short jaunt will be to the auto parts store.

 

[SeisMec]

I'm pretty much in the dark here trying to figure out if my girlfriends car needs a battery or a mechanic. Is there a definitive way to test a battery with a cheap analog multi-meter or am I going to need a load tester?

Are the low end ones adequate for occassional home use? I see some digital ones below twenty dollars but I try not to let low cost guide my purchases.

Any advice is truly appreciated. I didn't learn these things as a carpenter or by wheeling steamboats.

LED based testers marked --- FAULT, GOOD, FULL. ... --- next to each LED are IMO a waste of money and time. They are targeted at people who want low oil warning lights on their car's dash instead of oil pressure gauges.

Decent digital testers have screens that provide numeric measurements in addition to determinations like 'GOOD' or 'HEALTHY'. I've had this $55 tester for about two years now (tested 20-30 batteries so far) and have been extremely happy with it. (Not as nice as a Sun carbon pile load tester with inductive pickup amp meter, but good enough.)

If your test equipment is a multi-meter and a battery charge -

1. Look up the car's manufacturer's recommendation for minimum CCA (Cold Cranking Amps).
2. Cycle head-lights on for 20 to 30 seconds to blead off any surface charge.
3. Disconnect both battery cables. (Negative 1st).
4. If matting surfaces of the cable terminals and battery posts are not BRIGHT AND SHINY,
   clean them until they are BRIGHT AND SHINY.
   This cures about 50% of all starting problems.
5. If at all possible, check that electrolyte level of each cell is above the plates. Can be done on most "maintenance free" batteries by removing the label and prying up the glued down covers - see YouTube. Only use distilled water to top off.
6. Check the voltage at the battery posts. If below 13.2 volts, charge the battery; blead off surface charge and retest voltage. If you can't get the battery up to 13.1 volts, replace it. Like 2"x4" lumber, the 12 volt number describing automotive batteries is nominal. A new fully charged battery should read at least 13.2 volts and may read up to 13.5 volts or so.
7. If you got the volts up to 13.2 volts or more
   AND also had to clean matting surfaces
   OR also needed to top off electrolyte,
   then you have a very good chance the problem is solved. Maybe just reconnect the cables, roll the dice and call it good.
   Otherwise take the fully charged battery to a parts store and have it load tested.
   Or if you decided to spring for a digital tester that determines CCA by measuring resistance, use that. (It's menus would lead you through the same steps - except the menus neglect the clean connections and top off electrolyte advice.)

 

[2ndGearRubber]

The only way you're going to see 13 volts on an automotive battery, is if you have a fat surface charge on it. Generally accepted number for a fully charged battery is 12.6 volts DC.

Honestly I cant remember the last time I did a battery measurement that was much above 12.3. Reality vs. Engineering and Marketing documents.

 

[engineer2]

12.67 is the nominal voltage for a fully charged lead-acid battery with the surface charge removed. It can be a bit higher for some variations of battery chemistry (more antimony), but not lower.
The OLD rule-of-thumb was no lower than 9.6 volts while cranking the engine. You need to keep the engine from starting to get a bit longer cranking time though. (disable ignition or fuel system which can be a PITA on some vehicles).

 

[SeisMec]

12.67 is the nominal voltage for a fully charged lead-acid battery with the surface charge removed. It can be a bit higher for some variations of battery chemistry (more antimony), but not lower.
The OLD rule-of-thumb was no lower than 9.6 volts while cranking the engine. You need to keep the engine from starting to get a bit longer cranking time though. (disable ignition or fuel system which can be a PITA on some vehicles).

You are correct. And I must eat some of my words and many of my numbers. Faulty memory I guess. For more than 4 decades I've always been in a position to check charging voltage and then swap batteries with a matching vehicle with no starting problem. If the fault stayed with the vehicle, more diagnosis was needed. If it followed the battery = replace battery.

Last time I was on the selling end of a new battery was in a small service station in the mid-seventies. Batteries were shipped dry and for all but the most common sizes, the acid was added immediately before they were sold. In the winter (northern central plains) we routinely charged the freshly filled battery for thirty to forty minutes and then checked volts & amps. Would like to swear to 13.2 volts as per book, but maybe that's more faulty memory.

Words & numbers I'm unwilling to eat:
Bright, shiny connections cure about 50% of all starting problems.
Always check electrolyte levels. Low electrolyte is probably the reason for another 5% or so of starting problems.
Be sure every attempt has been made to bring the battery to full charge before taking it to a parts store to be load tested. CCA cannot be determined unless the battery is fully charged.

 

[Dandy1008]

Not a load tester, but a charger. I have had pretty good luck with these chargers. Hook them up and they will indicate if the battery is bad and potentially give you the reason depending on the code. I have yet to have the charger indicate a bad battery and it not be bad based on the load test at the local Battery or Auto Parts store.

Schumacher SC1359

Sorry - I cannot put in a link because I am a new guy. Available on a Prime Day deal for $58.98 on Amazon

 

[bwringer]

Quick and dirty load testing:

- Volt meter on battery. Read voltage. Ideally above 12.6V. 12.4V OK.

- Turn key on. Turn on lights, fan on high, etc. Don't start the car; you're just putting some loads on the battery. Voltage will sink slowly, but will stabilize around 12V. With a bad battery, the voltage will sink pretty quickly into the 11V range or below.

You can do an imprecise version of the above without a volt meter, at least on cars and bikes with halogen headlights, by simply turning the lights on and observing the color and how fast it changes. If it's yellow or goes yellow and dim within a few minutes, your battery is weak.

 

[Wrench97]

12.67 is the nominal voltage for a fully charged lead-acid battery with the surface charge removed. It can be a bit higher for some variations of battery chemistry (more antimony), but not lower.
The OLD rule-of-thumb was no lower than 9.6 volts while cranking the engine. You need to keep the engine from starting to get a bit longer cranking time though. (disable ignition or fuel system which can be a PITA on some vehicles).

This^^^^ for as much as you'll use the battery tester is a waste of money a decent one will cost you north of $300 the $20 load testers are only putting a small load on the battery the starter and a volt meter will give you a more accurate picture of what is going on.

@engineer2 Most modern cars have a clear flood mode, by holding the fuel pedal to the floor while cranking the ECM does not fire the injectors.

 

[2ndGearRubber]

@engineer2 Most modern -domestic - cars have a clear flood mode, by holding the fuel pedal to the floor while cranking the ECM does not fire the injectors.

Not all the imports have the figured out yet. Very annoying.

 

[engineer2]

Always check electrolyte levels.

This is great advice. Many people assume all batteries these days are maintenance free.

Not all cars have clear flood mode. I've been surprised by a few. If you know the vehicle, you know which fuse or relay to pull, or University of YouTube will tell you. Nothing wrong with a good battery load tester.

If you want a vintage load tester: VAT 40 prices have come down lately.
A Bear ARBST is good too since it will read engine rpm off the battery.

 

[SeisMec]

A Bear ARBST is good too since it will read engine rpm off the battery.

Just off the battery? Any idea how it manages to do that? I can picture reading starter rpm. But how does it make the leap past starter/ring gear tooth counts? Just curious - not looking to argue.

 

[Mechanical Noise]

... the $20 load testers are only putting a small load on the battery the starter and a volt meter will give you a more accurate picture of what is going on.
.

The $20 HF tester puts a 100A load on a 12V battery.

 

[engineer2]

Just off the battery? Any idea how it manages to do that?

Anything electrical on a running or cranking engine produces electrical noise that can be seen at the battery with an oscilloscope. Residual ignition spikes at the battery indicate RPM. You still have to punch in the number of cylinders and type of ignition. See patent 5004979. It's an interesting read.

 

[SeisMec]

Anything electrical on a running or cranking engine produces electrical noise that can be seen at the battery with an oscilloscope. Residual ignition spikes at the battery indicate RPM. You still have to punch in the number of cylinders and type of ignition. See patent 5004979. It's an interesting read.

I'm not an engineer so "residual ignition spikes" is enough info for me. Wouldn't have guessed (but should have guessed) that would be resolvable at the battery. Thanks for the info.

 

[zendriver]

The $20 HF tester puts a 100A load on a 12V battery.

It can’t work right, if it’s not expensive. [emoji57]

If anyone has the heebie-jeebies about buying one from Harbor freight, buy one from any other company (even Napa )selling at a similar price.

That battery tester design, has only been around 60 years or more

This seems like another one of those threads where somebody wants to build a doghouse and they are receiving plans for the Taj Mahal

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[richfinn]

I do a lot of battery tests on cars (roadside assistance)

We have a fancy Midtronics tester issued (which is ok)

In the old days we just used a voltmeter a jump pack and a DC current clamp hooked around battery negative to look at battery current absorbtion and drain

My vote for cheap DIY battery testing goes for a DC current clamp (and maybe a breakout cable for battery negative for access) it doesn't matter if its a dedicated clamp meter or one that plugs into a DVOM or scope

Load testers have had their day IMHO, enhanced flooded and AGM batteries need a more modern approach

The comments about "shiny connections" are valid I do find a fair few high resistance points, but I dont look how clean they are, I "volt drop test" with a DVOM and it takes about 30 seconds to do the whole system!!!

You might like some of these articles by Joe and others

https://vestest.com/testing-and-troubleshooting/?v=a284e24d5f46

 

[dogdog]

I would go for the HF one for home use... not something super critical... battery either holds charge or dead if you let it discharge too long... most of the time it will never recover.

there was a time I have looked at the midtronics battery analyzer if you can find a good deal at ebay. or pay the $$$ for it... me I just bring it to autozone and have them test it in exchange to listening to their sales pitch.

https://www.harborfreight.com/100a-612v-battery-load-tester-61747.html

https://www.jbtools.com/midtronics-...-electrical-system-analyzer-kit-with-printer/

 

[dogdog]

It can’t work right, if it’s not expensive. [emoji57]

If anyone has the heebie-jeebies about buying one from Harbor freight, buy one from any other company (even Napa )selling at a similar price.

That battery tester design, has only been around 60 years or more

This seems like another one of those threads where somebody wants to build a doghouse and they are receiving plans for the Taj Mahal

Sent from my iPhone using The Garage Journal mobile app

dam right all these digital electmatronics have make us dumb. Basic tools doesn't do fancy pixie dances is a useless tool for tool collecting and a fool will never like those tools.

 

[lardy1]

This has all been helpful to me. And in true GJ fashion, yes, it got more technical than I needed or can immediately comprehend, but I expected that and tried to learn from it. I appreciate ALL the input.

I am pretty comfortable in measuring it as it's cranking for a few seconds. It only drops to ten on the analog gauge. The battery rarely reads very much at all over 12 when I'm confident it is charged and I've ran the headlights for a couple minutes. I've checked every other battery that I know to be good and get about the same reading so I'm not concerned with that either.

I'm leaning towards ****** terminal connections. The Ford Edge is notorious for that. Short jaunts and carry the jump starter for awhile and keep taking readings.

 

[joel63]

I do a lot of battery tests on cars (roadside assistance)

We have a fancy Midtronics tester issued (which is ok)

In the old days we just used a voltmeter a jump pack and a DC current clamp hooked around battery negative to look at battery current absorbtion and drain

My vote for cheap DIY battery testing goes for a DC current clamp (and maybe a breakout cable for battery negative for access) it doesn't matter if its a dedicated clamp meter or one that plugs into a DVOM or scope

Load testers have had their day IMHO, enhanced flooded and AGM batteries need a more modern approach

The comments about "shiny connections" are valid I do find a fair few high resistance points, but I dont look how clean they are, I "volt drop test" with a DVOM and it takes about 30 seconds to do the whole system!!!

You might like some of these articles by Joe and others

https://vestest.com/testing-and-troubleshooting/?v=a284e24d5f46

Thanks for sharing this excellent website.

A ton of useful information.

 

[MoonRise]

I got the HF battery load tester a bunch of years ago. The '500 amp' unit IIRC.

Has helped me pretty quickly diagnose several iffy batteries over the years.

A quick check on their website, and here is the current (no pun intended) unit. Mine's blue though.

https://www.harborfreight.com/500-amp-carbon-pile-load-tester-91129.html

Well worth the $50 or so (use a coupon or a 'sale', like most things from HF).

I did replace the clamps. Had to, I melted one.

Let's me put a variable current load on the battery and not have to dance with holding multiple test leads/probes onto things at the same time. Put the clamps onto the battery, adjust the 'load' knob as desired, look at the built in voltmeter needle on the tester, it 'beeps' after the test time is done. Turn knob back to 'zero', take clamps off battery, done.

Let the tester cool off after use!!!!! Do not run back-to back high amp tests, you can melt or do other 'bad' things to the guts or cables of the tester. Remember where I said that I had to replace the clamps?

 

[Iowafox]

For me I got the Harbor Freight one for $14 and it's worked perfectly. It isn't fancy but works I got mine to test my batteries before winter comes and just to do the occasional test to make sure there all up to snuff. I am a weekend mechanic as a hobby but mine shown the same reading the autoparts store readers told me. So it's worth it to have and use randomly in my books.

 

[theoldwizard1]

The simplest way to check a starting battery requires a GOOD battery charger and a decent multi-meter.

• Disconnect the battery from the vehicle. Charge the battery for at least 12 hours. Remove from charger for at least 30 minutes. If you aren't close to 12.8V, don't go any further. The battery is dead or will be soon.
• Reattach battery to vehicle and wait 10 minutes. Do not start. Battery voltage should still be about 12.6V. If not, you are loosing power somewhere.
• Do not start the car but turn on headlights, bright lights, interior lights fan and stereo. After 10 minutes, it still should be above 12.2V and the car should start.
• If it cranks slow, you have a bad connection (positive or negative) between the battery and the starter

 

[Coach James]

I got the HF battery load tester a bunch of years ago. The '500 amp' unit IIRC.

Has helped me pretty quickly diagnose several iffy batteries over the years.

A quick check on their website, and here is the current (no pun intended) unit. Mine's blue though.

https://www.harborfreight.com/500-amp-carbon-pile-load-tester-91129.html

Well worth the $50 or so (use a coupon or a 'sale', like most things from HF).

I did replace the clamps. Had to, I melted one.

Let's me put a variable current load on the battery and not have to dance with holding multiple test leads/probes onto things at the same time. Put the clamps onto the battery, adjust the 'load' knob as desired, look at the built in voltmeter needle on the tester, it 'beeps' after the test time is done. Turn knob back to 'zero', take clamps off battery, done.

Let the tester cool off after use!!!!! Do not run back-to back high amp tests, you can melt or do other 'bad' things to the guts or cables of the tester. Remember where I said that I had to replace the clamps?

Moonrise, I have the same tester, also blue from HF. Do you set the CCA as directed in the directions? I have seen several videos of guys claiming the written directions are wrong and the CCA should be set the same as the battery.

Coach

 

[MoonRise]

Moonrise, I have the same tester, also blue from HF. Do you set the CCA as directed in the directions? I have seen several videos of guys claiming the written directions are wrong and the CCA should be set the same as the battery.

Coach

Directions?

I have usually turned the knob until the amp draw on the CCA scale on the meter is pretty much the same as the CCA rating of the battery, or close to it. If the voltage meter still shows 'green' (using the adjusted for temperature voltage scale), the battery is good.

And yes, the unit does indeed get warm/hot internally. Several hundred amps, even for just 15 seconds (the test time) can warm things up.

LET THE METER COOL OFF AFTER A TEST!!!!