How to Tell if Your Car Battery is Really Bad - Page 1
Forum section: electronics / general

author: golden_labels
author_rank: Super Contributor
timestamp: July 03, 2019, 01:34:23 am
content: What is the actual theory and technology behind the tester? The guy uses some vague, non-technical terms and doesn’t explain anything, just treating the “smart tester” as a black box.

author: floobydust
author_rank: Super Contributor
timestamp: July 03, 2019, 01:41:34 am
content: It's an Interstate Megatron, la garbage!Interesting comparison between hydrometer, load tester, and the ESR? tester. Clore Automotive is in the Malware Domains list, and the domain does not exist, so I could not look at it further.edit: found the patent for the Midtronics battery conductance testerUS7058525.No mention of the pulse currents used, but it's pretty straightforward.It looks like a superiour way to find plate active area (capacity) in lead-acid batteries of all types. I'm tired of looking at cell voltages to try figure that out.

author: David Hess
author_rank: Super Contributor
timestamp: July 03, 2019, 03:49:03 am
content: A common failure is the cracking of a plate so that one cell becomes high impedance. The voltage with low load current will be almost normal but at higher currents, the voltage will drop. A low frequency internal resistance measurement would detect this.

author: floobydust
author_rank: Super Contributor
timestamp: July 03, 2019, 04:09:52 am
content: Sulphate crystals also cover the plates as an insulator, to get the same result - less capacity, higher impedance.The tester is probably a few amps current drain pulse and they are using 4-wire connection to look at the dynamic battery voltage sag. Somehow the measured ESR is extrapolated back to cold cranking amps.

author: rstofer
author_rank: Super Contributor
timestamp: July 03, 2019, 10:22:05 pm
content: An old fashion analog multimeter is a great way to test batteries. Just connect it up and hit the starter. See how far the voltage drops. If it drops a lot, replace the battery. It simply doesn't matter why the battery can't provide cranking current without dropping voltage, replace it.Cross check with a known good battery or even the new battery you install. Just to get a sense of how it ought to work.

author: Seekonk
author_rank: Super Contributor
timestamp: July 03, 2019, 10:27:23 pm
content: It was last fall and my car battery was over 4 years old. I figured I'd get new battery and use the old one at camp for something. A couple of months later new one would be dead in the driveway or after driving around it would say going into battery saver mode immediately after turning the key off. The battery would instantly go to very low 12V. No phantom loads. Brought it back and the whiz bang wifi connected battery tester said it could do 740A. Tech said he would give me a new one, but I could never come back. Everything has been fine for half a year. That box was impressive looking!

author: Circlotron
author_rank: Super Contributor
timestamp: July 04, 2019, 01:33:49 am
content: We just accept the fact that lead acid batteries have a limited life and eventually wear out. Imagine if a battery came on the scene that had an indefinite life, and after some years the cost dropped to a negligible figure. We would feel a bit like people back in the day when transistors began to replace vacuum tubes.

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 04, 2019, 01:43:21 am
content: Quote from: Circlotron on July 04, 2019, 01:33:49 amLiFePO4 is pretty close to that - on the order of 10 years or more of service life.

author: capt bullshot
author_rank: Super Contributor
timestamp: July 04, 2019, 06:31:23 am
content: I think, car battery heavily depends on usage and environment, but there's a wide range of "quality" available. I've made the (repeating) experience the originally supplied car battery lasted longer than 10 years, but the replacement (bought whatever was available and looked somewhat decent) never could compete with that.

author: Shock
author_rank: Super Contributor
timestamp: July 04, 2019, 07:27:23 am
content: This device is unnecessary, you just need a load and a voltmeter/dmm. The first device was showing very rapid drain after being charged to full capacity, which simulates the exact problem the car is going to have.Quote from: golden_labels on July 03, 2019, 01:34:23 amSeries resistance calculation with some stored profiles to compare against a new battery.

author: tkamiya
author_rank: Super Contributor
timestamp: July 04, 2019, 03:37:28 pm
content: Just turn the head lights on without starting the car. If it barely glows, it's really bad. This trick may not work with LED headlights though.

author: Shock
author_rank: Super Contributor
timestamp: July 04, 2019, 06:43:19 pm
content: Quote from: tkamiya on July 04, 2019, 03:37:28 pmWell the video mentioned nothing about other problems like parasitic drain or shorts. But the good thing about doing the test at battery (and even isolating it if you have to) is less chance of other faults leading you to think it's your battery when it isn't. The lights when they get water in them is one of those problems.

author: floobydust
author_rank: Super Contributor
timestamp: July 04, 2019, 06:58:11 pm
content: GM, Ford, Tesla have many patents for using ESR to determine battery capacity.It's modern tech that is important for electric cars, so why not use it on lead-acid batteries? It's quite a linear relationship between ESR and capacity.The car headlight test says nothing about capacity. A 10A load and a voltmeter tells you a little bit about state-of-charge but not much about plate corrosion, if the battery can put out 200A to crank a car. I've seen it many times, you get 12V at light loads and nothing to start the car.

author: DimitriP
author_rank: Super Contributor
timestamp: July 04, 2019, 07:17:04 pm
content: QuoteToo proactive to be a good thing for battery/car manufacturers.If your battery dies and you can't (too far / time crunch ) take it in under waranty, the manufacturer is off the hook.Some people believe that all the tech going into cars is for the benefit of the car owner/driver / passengers.And although the above mentioned entities enjoy some benefits, it's a side effect of manufacturers adhering to rules/laws or doing things for their own benefit in some way or another. </cynical>Talking about monitoring and predictive failures etc...how many of you ever had a hard drive replaced under warranty because of a S.M.A.R.T. report . Its also possible that no drive ever had "bad S.M.A.R.T. " counters during the warranty period.

author: richnormand
author_rank: Unknown
timestamp: July 04, 2019, 10:41:33 pm
content: In the video on the topic of testing the electrolyte density (sulfuric acid to water content) he only tested one cell. No way you can tell the status of a battery until you test all cells.I have seen many issues where one cell density was off although the overall voltage was fine.The battery was OK for voltage and low amps until a real heavy load was applied due to the increased internal resistance of that cell. Also in many cases there is a darkening of the electrolyte at that cell.Best test overall test is put the battery on a charger for 15min, then (in Canada at -35C) is to read the voltage at the battery posts while cranking a cold car. Then read the voltage at the engine block and alternator to detect any corrosion along the way to sort out a bad contact or the battery.

author: floobydust
author_rank: Super Contributor
timestamp: July 04, 2019, 11:20:43 pm
content: Specific gravity tells you state-of-charge but nothing about capacity. He got 1.250 on the one cell and 13.17V looks great. But how much of the plates are active?The ESR tester gave 600CA on a 940CA rated battery, 64% capacity and it got an overall fail. Yet it's fully charged.I'm not pissing around with a car battery at -35°C to test it! Your hands are frozen, the multimeter is frozen, the test leads snap from being brittle!A smart man replaces the battery before it can fail in winter and that's the point of using ESR.You guys and these cheezy load tests need to realize that a battery's state-of-charge has nothing to do with its capacity.

author: SilverSolder
author_rank: Super Contributor
timestamp: July 05, 2019, 12:13:00 am
content: Quote from: rstofer on July 03, 2019, 10:22:05 pmExcept when you get fooled by the starter motor drawing too much current, prompting you to replace the wrong component (ask me how I know!)