Yes. This is even a better test in cold weather because your your starter requires more current and your battery has less to give. If your battery voltage ever falls below 9.6 volts, it is in danger of not having enough voltage for the ECM to control injectors, ignition coils, and other essential components.
My fluke 87 has found its way to the graveyard. I bought it in 93. Used it everyday. I had minor problems with screen. Replaced it with the 87V. As good as they are they are only as good as the person using them. Fluke makes a great product. Thanks for posting your test.
From viewing your video my Fluke just paid for itself. Have had battery failures ruin my day more than once. This time, using your test, I can see what's coming far enough in advance to avoid the hassle. Have tested my current battery every six months or so since new. This morning for the first time, starting-load voltage showed way low so I have my "warning" before I have to deal with the hassle of an actual failure. Good on ya!
Dramatically fantastic. Min/Max multimeter is essential for the test, because of this I’ve purchased aneng an m118A cheap multimeter. Greetings from Saudi Arabia.
Thank you for making a good video no stupid background music no idiot trying to act like he has this awesome personality no babbling on and on and I just good Claire English thank you !
it is highly recommended to do the test for 11-15 seconds ..the easy way to do it- WOT with min-max and don't forget to do avg reading too ..this is just in case you suspect your battery is weak usually i do the 20Sec to be in the safe side and i always use the chases ground or engine ground ..Good video justin
Fantastic! I am so glad I found your video. I nearly went out and bought a battery drop tester, when it turns out my Fluke will do the job! Thanks ever so much.
Great vid. At first I wondered why the meter had to have a min/max function. Why not just watch the meter? Then I saw that the lowest voltage that showed on the meter was 10.42V. But the min/max reading showed 9.96V. So now I know. Thanks!
I don't consider myself an expert at anything. But a few comments. The 9.6 volts number is only a magic number at 60 degrees Farenheit and above. According to my resources, the magic number is 8.5 volts at zero degrees Farenheit. So the magic number is on descending sliding scale of about 0.15 volts less per ten degrees temperature drop. Also, you don't have to have an expensive multimeter with the min/max function. You can accomplish the same thing by pulling the central wire on the distributor (or otherwise disable the coil), and dead-crank the car for 15 seconds while watching your cheap multimeter. Observe the meter while dead-cranking. If voltage stays above 9.6 during the 15 seconds (at 60 degrees F or above), your battery is good.
I suppose that 9.6 volts is only a magic number because it is a fairly good "average" number for determining whether the battery passes or fails. I have found that if I use a fast lab scope (like a Pico scope) for the same test, 8.0 volts seems to be the magic number. The reason for this is that when the starter first energizes it usually draws between 600-1200 amps for a split second. During that split second when high current is being drawn from the battery is the time to see how well the battery can maintain its voltage while delivering high current. For that reason, the test will not work without the min/max function or a lab scope. This is not the voltage during cranking, but the voltage during initial energization of the motor.
That is a very true comment--thank you! If the starter has shorted windings or if the engine itself is seized, starter current will be excessive and could put too much of a load on the battery, causing the voltage to drop lower than it would under normal circumstances. While a starter problem like this is not common, you should fix any starter issues before relying on this test to condemn a battery.
Hi Justin, thank you so much for this very informative video, it was the exact information I was seeking. One month ago, my 41-month old Interstate battery nearly left me suddenly stranded upon initial morning startup (car always garaged) despite being plugged into my Battery Tender Plus with its steady green light showing a fully charged battery (I always keep the tender connected whenever the vehicle isn't driven). I lucked out when the car slow-cranked but started on the THIRD attempt (a miracle). I replaced the battery and have been monitoring it during startup ever since with a DVOM and digital camera, which I now realize was useless (thanks to your video) since mine doesn't have MIN/MAX functionality. Prior to finding your video I purchased an OptiMate TS-121 device, manufactured by Tecmate, which conveniently plugs into the SAE connector already attached to my battery (for my Battery Tender Plus) -- the TS-121 provides a visual representation via a series of LEDs to capture real-time resting voltage, lowest cranking voltage, and charging voltage all-in-one fell swoop, which the manufacturer claims are true depictions due to the unit's "microprocessor accuracy." I'm wondering what your thoughts are of this handy device, and whether I'd be better off just returning it and purchasing a MIN/MAX DVOM instead (price of the TS-121 was just under $50.00). Would I only be able to confirm the accuracy of the TS-121's lowest cranking voltage LED result by checking it against a MIN/MAX-equipped meter with both connected to the battery simultaneously? I'm not sure I have full confidence in the TS-121 cranking voltage results since a few have read lower than I expected given my brand new battery, despite the product's glowing online reviews (the resting voltage and charging voltage LED results have been dead accurate with my DVOM results). You can see the TS-121 in operation here: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-XDuaz-NlQo8.html . Thanks.
Only a meter with a min/max function will be accurate enough. The only thing better than that would be a digital oscilloscope (PicoScope). If you want a budget meter that actually does a really good job, I would recommend the AstroAI DM6000AR on Amazon. For about $30, they do a pretty good job!
Hey Justin, please confirm. I was taught that the battery should maintain 9.6 Volts or higher at vehicles maximum load for 15 seconds. I have seen this test performed with a multimeter but only after disabling the ignition system to prevent start and to have starter actively engaged for 15 seconds without the battery dropping below 9.6 Volts. I am tracking 100% of everything else but timeline of the test. Thanks. DP.
Good information. I know about needing to test a battery *under load* for any kind of useful results, but I appreciate the details and threshold voltage of ~9! Also a good mention about the over-voltage that can only happen when one's alternator is giving at least a fair bit of current, I would imagine. While of course not equivalent to an actual alternator tester, it's a handy indicator. If the amperage were low, I'd think the battery would consume any additional voltage, but I'm not certain..
If the battery is barely above 9.6 volts, it is good enough to start the car, but barely. You can check it again in a couple of months - or replace it if you are unsure and there is cold weather coming. If the voltage is well into the 10-11 volt range, your battery can easily start the car and you should usually only need to check it once a year before the winter months.
Justin Miller Hey I just purchased a battery did the the multimeter test with engine off the reading was good 13 point fifty something or sevety something but when he switch the enging on, headlights and A/C on as well the reading dropped to 12 point fifty to seventy something. The guy doing the test said there was a concern for the alternator and advused me to get a second opinion from an electrician. Do you think that there would be any concern as such???
while engine is running, meter must read above 13.4V (keep AC off). If it is not, alternator is not giving output. CAUTION: NEVER remove any battery terminals to check the output on running engine, it may fry your computer.
It seems you need a multimeter that has a min-max function, and a quick enough display rate to capture that minimum voltage - that Fluke looks good - about 3 refreshes per second or more, I am guessing. I'm not sure that all digital meters are quick enough.
You got claws on your meter, mine has needles. Just a tip if you have a needle meter you probably have to loosen the nuts and put the needle in and then tighten the nuts. Anyway I did not even notice the max min switch on my meter. But all is good I got 9.64 and then 9.66 so my car passed the test. Will test again in 6 months. I think there is another test called the Safari Park test, driving 5 mph for 2 hours. Though I like your test better. Will have to check more of your videos.
Prevent engine firing by sealing the transponder key in foil (earthed or grounded). Crank engine for 10 seconds and voltage should not drop below 10v. Batteries rarely last longer than 5 years so replace it before it fails and leaves you stranded!
Found answer:- test procedures according to sae j537, ice and din Fully charge battery according to SAE J537 and cool to -18°C (0°F) for 24 hours. While at subfreezing temperature, apply a discharge current equal to the specified CCA. (500 CCA battery discharges at 500A.) To pass, the voltage must stay above 7.2V (1.2V/cell) for 30 seconds. Fully charge battery according to ICE SAE J537 and cool to -18°C (0°F) for 24 hours. While at subfreezing temperature, apply a discharge current equal to the specified CCA. (500 CCA battery discharges at 500A.) To pass, the voltage must stay above 8.4V for 60 seconds. Fully charge battery according to DIN SAE J537 and cool to -18°C (0°F) for 24 hours. While at subfreezing temperature, apply a discharge current equal to the specified CCA. (500 CCA battery discharges at 500A.) To pass, the voltage must stay above 9V for 30s and 6V for 150s.
The traditional carbon pile test that you mentioned and the test that I presented in this video are both load tests. Batteries degrade over time. The question is, "when is it time to replace the battery?" The carbon pile test measures the battery against the battery manufacturer's ratings. The multimeter test uses the vehicle's current requirements as the standard. Once a battery is put into a car, ratings don't matter anymore. We just need to know if it will reliably start the car.
The current required to turn the motor can be affected by mechanical factors, as well as starter drag from a bad armature or brushes etc.. It can be very hard to determine whether the battery or starter motor is at fault sometimes...
A good way to put a load is to turn on your high beams on for 3 mins den turn them off and get ur readings less then 12.45 or 75% its needs to be charged
I like the video it told me what I needed to know. But I think it's funny that you test the battery's. Ability to start the car by using it to start the car. Just kind of a one of those face palm moments that I know isn't really dump. Still got a chuckle out of me
Nothing like a Fluke, I have performed this test on my car but haven't had the same results,I get these weird readings,I think is because my leads are not alligator clips and they are not making good contact, my first reading is like 5 but I know my alternator is in decent shape,then I get like a 00 lol great video anyhow, thank you!!
Thanks . Now I know the use of the max button. But I want to ask, the 9.6 v you referred to what is it? I thought it's a 12volt battery why did you reference 9.6v?
This is a decent approximation of a proper battery load test (and it's the way I've been testing my motorcycles and cars for years), but it is not as accurate as tests run with a carbon pile to provide the prescribed load (1/2 the rated CCA) for 15 seconds while observing voltage. Marginal batteries can pass the quicky test, but fail the full load test. When I check my vehicles I disable the ignition or injection and run the starter for 15 seconds while reading voltage. I've found that to be a closer approximation to a test run with a real battery load tester.
Not to get too philosophical here, but what does it mean to be accurate in a battery test? Any test is only an approximation based on standards we have invented. The min/max test in the video checks the voltage of the battery while it is supplying current to the starter. The carbon pile load test measures the battery's voltage while supplying current to a carbon pile tester. Someone arbitrarily determined that this load should be 1/2 the CCA rating. Which test is better or more accurate? This depends on what your definition of a "good" battery is. Is it more important that the battery can meet the standards that it was originally rated for or that it can reliably start the vehicle? Also, accuracy requires repeatability. Can these tests be repeated many times with exactly the same results? By the way, if you want both accuracy and precision, I would recommend measuring battery voltage and current with a lab scope while starting the engine.
Why do we not see AGM batteries in cars ? Lower maintenance, faster charging, can run lower without damage, installed at any angle, combined deep cycle and cold cranking....
We are actually seeing more and more AGM batteries in cars today. The reason that they are not used everywhere is that they cost more than conventional batteries and they don't provide much advantage for a typical car owner who drives the car daily or nearly daily. Conventional batteries work really well if they are maintained and they are not cycled. Of course the lifespan of any battery also depends on its quality. Some brands are much better than others.
Today the rule of thumb is 10V if using a DVOM and no lower then 8.5V on the current in rush then a 10V cranking voltage when using a scope. I use a meter with a DLC break out box to and disable the car from starting like clear flood crank mode then crank it for 5 seconds . If it can maintain 10V for 5 seconds then I'm happy.with it
If above 9.6, How often should this test be done to ensure the battery is still good? And should this test provide the same type of results with a boat battery / motor startup? Cheers.
If the battery does go below that reading, does it need to be replaced? Helping my friend determine why his car isn't working properly. Battery reads 12.4 (i didn't perform this test yet) Tries to start, and the belt starts to rotate but alternator never turns over. Thinking we have a battery problem. maybe a starter issue. Car wouldn't even start while getting jumped. Thanks for response
good video and well explained.this min/max function is so handy here. But i was just thinking would you not disable the car from starting and keep it cranking for 8-9 seconds to give the battery a more of a test...
When using the min/max function, you do not need to crank for longer. The lowest voltage you will encounter is during the split second as the starter motor begins spinning. For just an instant, the starter motor could draw 500-1000 amps, which will pull the voltage quite low. Cranking the vehicle for longer will not give you any more information than you already have.
Thank you for this video. Noticed your pop up at 2:26. Could a low voltage of 9.98 with a brand new Interstate battery also be the result of a dirty ground connection somewhere between the starter and the battery? I already checked my compression and took off all the fan belts to see if there was any additional drag on the starter and there was not. Also replaced the starter since it was over 10 years old and had many, many short trips in 78,000 miles.
looks pretty ridiculous to me, if you have a battery that doesn't have the capacity to start the car then how does the car start in order to start and test.
Well that's one way to look at it. If my credit card didn't get declined then I must have plenty of money and there is no need to check my bank account :) Seriously, if your car doesn't start, it could be caused by things other than the battery. It is good to know how to check your battery to see if it is the cause!
12.4 volts can be very misleading, due to if the car was recently driven, and-or battery recently charged, this would be 12.4 " Surface-charge" . True test with pudding, time battery sits, engine off, battery not charged. 12.4 holding post wait time, is 12.4 accurate battery test.
That is correct. I wanted to keep the concept simple in this video. I have a separate video about determining a battery's state of charge. If the voltage (state of charge) is below 12.4, you can still perform the test, and if the battery passes, great! If it fails, you should charge the battery and retest it.
No, you do not need to disable anything. That is why we are using the min/max function. It allows us to capture voltage in the moment the starter begins to spin, before the engine has a chance to start.
Scott Thomson . Yes it can , you can have good voltage but not enough amps to crank a engine over in cold weather. You know like Buffalo N.Y winter's. lol
Do multimeters have the sampling frequency to give accurate results in this kind of test? The voltage can change so quickly that the meter simply may not register certain spikes. Am I mistaken?
No, all multimeters are not the same. This test can give you varying (although similar) results depending on what meter you use. I would recommend a higher quality meter with a higher sampling rate. If you have peak min/max, that will also increase your sample rate. Either way, do this test 2-3 times to get a good average reading if you are uncertain.
The cables are connected to the battery, but all of the switches are open. So, until you close a switch (such as the headlight switch or ignition switch), you are measuring open circuit voltage.
I keep reading/hearing that if the battery is 'below' 12.4 volts, then the battery has to be charged. If that's the case, does that automatically mean its a problem with the alternator if its a new battery? In other words, why wouldnt the battery be charged aside from it being an old worn out battery?
12.4 volts represents a battery that is 75% charged. This is the same concept as your cell phone or laptop battery. There is nothing wrong with a battery that is 75% charged, but if you are going to load test a battery, you would not want to do it when the battery is at a low state of charge. Otherwise, the battery could fail the test when the battery is still actually just fine, but in need of being charged. It is not uncommon for a battery to be less than 100% charged. If you start the car but don't allow it to run for at least 5 minutes, the battery will not be fully charged. On many cars, the lights and other accessories remain on after the engine is turned off, which can also drain the battery slightly. You would never throw away your phone battery because it was only 75% charged - eve if the battery was brand new. You would simply charge it.
What about on 2 battery system using our fluke 88v meter. Are you saying 19.2 is the lowest figure being 9.6 times 2? If below how do you know which battery not good
Two battery systems are still 12 volt systems - the batteries are connected parallel to each other in order to provide more current capacity. Do the same test. If the two batteries together can't maintain 9.6 volts when the starter motor is engaged, they should BOTH be replaced. The batteries work together and should always be equal to each other. Never replace only one battery or the weaker battery will drain the stronger battery, shortening its life.
To make 24vthey are not in parallel but in series. Pos connected to neg with outer pos and neg to truck. This voltage check to determine if the batteries are able to prove CCA is not flawless I think. Also a customers truck in the morning has no power to crank engine. I checked for parasitic drain and there was less than fifty millivolts being consumed. This means the batteries were faulty. The voltage was 13 point something which also goes to say the cells were nackered. They would stabilise if a charger put on them and the truck would crank 10 seconds after connecting just one charger to one of the batteries. A proper test is obviously a load test by a load tester. I used my fluke 88v in min max mode on this truck and on cranking the voltage went down to 21v. When I connected 2 brand new Yuasa super heavy duty batteries with 12.6v thereabouts the truck cranked no issues and also only then did the battery sumbol disappear on the dash. The symbol would not disappear with other batteries
thanks for the video, helped me a lot. Question: when buying a used (consumption not starter) AGM, what is the best method to test it? Should i set up a chart, measure VOC, put on a load and measure VOC again after some time has passed? (what is the best method to get an accurate indication on the health of an AGM battery?)
Yes. This would be a good test for almost any type of battery. It is just like determining the pressure/flow capacity of any fluid. You make it flow, and then check to see if the pressure is still sufficient while it is flowing. If the capacity or volume is too low, pressure will drop when it begins to flow. (Voltage = pressure, Current = flow).
I picked up a 6000-count multimeter with the MIN/MAX function, the meter has both auto mode setting (up to 750V) and manual mode settings (600mV, 6V, 60V, 600V, 1000V). Which meter setting would provide the most accurate 12V car battery voltage drop capture result, auto mode or manual mode (60V)?
Whichever range gives you the most digits will be most accurate. In this case, a 20V range would be ideal. If 60V is the closest you can get, you can use that. It usually works great in auto mode, as long as you connect your meter to the battery with alligator clips, and wait for the battery voltage reading before pressing the min/max button. Most meters do not auto-range after you have pressed the min/max button. Letting the meter read battery voltage first will put it in the right range.
so, does the battery have to be fully charged for an accurate load test? i just went to get my tires rotated and ford service claimed to do a load test without my request. they said the battery is bad but i've never had any indication of a bad battery. also, wouldn't they have to CHARGE my battery before the test? and why would they charge my battery for free just to do a load test a never requested? i'm suspicious of a scam. should i be? also, where's the date of installation on batteries? if i knew the date of installation it might give a clearer idea of whether the battery might be in need of replacement.
Yes. The battery has to be fully charged (or at least 75% charged) for an accurate load test. What they have told you is correct. Unless you have a receipt or the person who installed the battery marked the date, there is no way to know the installation date. However, there is often a serial number or manufacture date on the battery that can indicate when the battery was made.
So, if my multi meter doesn’t have min max, I can either have someone else start the car and monitor the meter, or set up a camera, maybe even set at high speed.
No, unfortunately it doesn't work that way. The multimeter can sample (or measure) the voltage of the battery between 100-1000 times per second, depending on your meter. The display on the meter only updates once per second on a good meter. A camera wouldn't help you. Also, the minimum measurement occurs during a split second when the starter motor circuit has been turned on but the motor hasn't begun to spin yet. At that instant, the starter motor can draw between 600-1000 amps, which pulls the voltage down. This is when we want to measure the voltage. You will need to have a min/max function or a lab scope to capture this.
Pragmatism suggests it's probably better to consider the criteria of this test and procedure as applicable to a 'cold start' (first thing in morning or after auto sits overnight). Eventually we need to buy a new battery and the more time we have to do this, the better we can shop for good value oR, like me, we'll have some time to visit the autoscrapyard and buy a melon under the condition of knife-slice-and-taste :D
That multimeter is $200. How can I accomplish this with my free harbor freight multimeter? Can I take a video of the readings and watch it back in slow motion or will the min reading flash faster than the speed of light
Yes, so long as your multimeter can respond fast enough to show the min and Max voltages. It has been my experience that even cheapo meters work fine, but have no min memory function.
