Why no simple gauge on a car battery to measure charge?

Factual Questions
21

Excellent point. Not only do they start on the first crank attempt, but also on the first or second cylinder to pass the firing point in the cycle. On an inline 4 that’s within 1 complete rotation and even less on a V8.

Back in the Ye Olden Dayes off Carburetors ynd Dragonnes ynd Suchy even a warmed up car in good tune often took several revolutions = 8-16 or more cylinder firings before it lit off.

Now it’s pretty much one and done. If the batteries’ got enough oomph to get past one or two cylinder firings, the car starts normally. And so the battery appears to be in good shape.

22

The AC conductance testers do a pretty good job of determining battery health. They aren’t perfect, sometimes they will pass a failing battery, but when they condemn a battery, it is defective. They’ve been used for warranty service for a while, because they are easy to use and don’t require a 100% charge for testing or re-charging after testing. They use the battery voltage itself to power the tester. Load testing is still the definitive measure but is time consuming. The conductance testers could easily be incorporated into the dash controls and would give a heads up when a battery is starting to fail.

One thing that will fool them is corroded connections.

23

I can’t speak to the EXACT thing the OP was hoping for in car battery monitoring, but I can fully support the gist of his overall complaint. There are plenty of things that car and other designers could build in to their products, which they don’t, only because they have their heads up their own kiesters.

I bought a thirty dollar plug-in reader device, to translate the meaning of the Check Engine light on my car.  It's obvious that since the already built-in car computer "knows" what the check engine light means, putting something on the dash which straight up tells us what it means, would be very inexpensive.  I suspect that they failed to do this on all cars yet, simply because they are stuck in some kind of past thought loop where the computers are just for mechanics to talk to.

I had an alternator failure last year. The car computer knew exactly what was going on, and could have told me straight up that the alternator was dead, so that I could have immediately gotten safely off the highway before the battery died. But no, I had to deal with a pair of indicator lights which said NOTHING about the alternator, and which contradicted each other logically, but which I was able to Google and discover the correct answer. The car maker didn’t even bother to put the answer in the owners manual, saying cryptically instead, that said indicators going on at the same time meant that I “needed to have the car serviced soon.”

I know it was thick-headedness on their part, because I’ve seen plenty of the same thing first hand.

One favorite small example from long ago now, was a copier designer/maker I worked for, who had built a new machine that could use various sizes of paper in each drawer. They had adjustments on the trays, and buttons next to the trays which the user had to press, after putting the paper in, to tell the machine what size paper was in what tray. Then they made the computer in the machine smart enough to post an error saying “paper size not correct” on the front screen. Finally, they built sensors into the thing, so that as it fed the paper, it could detect the paper size as it moved out of the tray, so it could warn the customers that they’d pressed the wrong button.

The design team was so stuck in the thinking that everything had to be set manually by the customer, that they sold hundreds of thousands of the things, before anyone noticed that the buttons could have been done away with from the beginning. The machine didn’t HAVE to stop and tell the customer to press the other button. The machine knew already.

24

The thing about battery chemistry, it was all hashed out a hundred years ago. So a “self test” analyzer wouldn’t be too tough to incorporate. Another basic test similar to the load test, is monitoring the voltage during engine cranking. Basically the ignition is disabled and the engine cranked over for 15 seconds. A healthy battery won’t drop below 9.6 volts @ 70F, that’s the minimum acceptable voltage. A newer battery won’t drop below 11 volts say.

There would be some benefit to a “battery weak” or similar indicator like CCA remaining. Usually though, as long as the engine starts most people aren’t paying attention to the battery. The battery light gives warning that the alternator isn’t charging properly, but I can see where an actual battery fault indicator would be useful. It would still be widely ignored?

25

Similar to the load test? That IS a load test.

26

This reminds me of the uselessness of most error messages.

I think it’s all because too little time is spent on planning for error conditions before the product is put on the market; how to handle them and what to notify the user. When products are first put on the market, errors are not all that common and the engineering mentality isn’t encouraged to dig into obscure error possibilities that might crop up. After all, most designers are no longer with the company by the time that a consumer encounters a mysterious error years later, and future incompatibilities are difficult to anticipate.

27

I just rig up dual battery systems in most of the stuff that I don’t want to be stranded in. :smiley:

Always carry an extra!

28

I sold car batteries in college. Often when a battery died suddenly as the OP’s did, low water in the battery was usually the cause. The sulfuric acid is mainly water. It evaporates gradually. The plates slowly get exposed to air, oxidizing over time, and eventually too much surface area isn’t producing the chemical reaction and the battery fails. We usually saw more batteries die in the summer than winter. I wonder why? :wink:

Think about the last time anyone mentioned checking their car battery’s water level? Exactly. [conspiracy voice] Big Car Battery convinced everyone batteries are maintenance free. [/conspiracy voice] Until they can change the laws of physics to eliminate evaporation and/or the need for vents in car batteries, car batteries need maintenance.

Rounding back to the OP’s request, engineers on this board could discuss how easily a "low battery water level"indicator could be added to a car. That’s beyond my scientific knowledge.

Checking and filling your battery with distilled water is shown on many websites on the Internet. Do so especially before long summer driving trips. [/public service message]
Note: None of this applies to gel cells.

29

Well it is “a” load test, but then so is turning on the dome light. The classic carbon-pile load test is to apply half of the rated CCA capacity to the battery for 15 seconds, a starter will draw a lot of juice but not that much, usually 150 amps for a V8 say, and less for 4 and cylinders. It is a VERY useful test for sure, but not quite as demanding. It can also give conflicting results if the cables and ground connections are defective, as is often the case.

What I think would be useful though, is some sort of lowest reading and “hold” indicator during start. Once batteries start to go they choke at starting, since that is by far the highest current demand especially in cold weather, the internal resistance increases and the ability to pass current goes down, while at the same time the current demand goes up due to thick crankcase oil for example.

30

Agree that starting is the severest load and so also the best place to read battery performance for predictive purposes.

At the same time, the value of a load test is that the load is calibrated such that you can measure the battery parameters and have something meaningful to compare them to.

The particular starter turning the particular engine in any particular car and connected through that particular set of cables and connections and corrosion will not be a calibrated load. Nor will it be a repeatable one.

None of this prevents a smart enough computerized system from forming an opinion over time of what constitutes typical performance for this particular battery in this particular car. And signaling a warning when performance deviates far enough from typical.

That still leaves us though with my objection from post #17. Now the battery warning is displayed, but the car still starts fine. How many drivers will replace the battery before it strands them 2 months later? How many will be happier to have had the warning vs. not?

Those are the tradeoffs IMO that are keeping battery health-o-meters out of cars. IOW, it’s quite do-able; it’s just not saleable.

31

IIRC, having a voltmeter and an ammeter on your car gives you more than enough information to keep an eye on battery health.

Voltmeter shows voltage, and ammeter shows how many amps are being charged or discharged.

32

Not really IMO.

They are enough to show you charging system health. But a healthy charging system connected to a weak battery will look normal on the gauges while the car is running, and will show ordinary voltage while the car is electrical-on/engine-off.

Yes, you’ll see unusually low voltage while the car fails to crank and instead goes “ker-chuunk, ker-chunk”, or worse yet “click, click, click, click”. But by then it’s too late; you’re already stranded.

33

What I recall (it’s been 20 years since my vehicle with both) was that you could get a feel for how long it took for your alternator to recharge your battery after starting by watching the ammeter. As the battery capacity changed, so did the pattern of how it charged- both time and amps. You had to psy attention over time though.

Sent from my SAMSUNG-SM-G900A using Tapatalk

34

Thirty+ years ago there was a good amount of merit to this. Nowadays, though, most car batteries are maintenance free, and the liquid can neither be checked nor added to. That said, maintainable batteries still exist but most current service personnel don’t check them, and you’re right that it’s a lamentable problem.

Very easily. Delco batteries had them decades ago. A few people even paid attention to the reading.

35

Not necessarily more than enough, but a significant amount. These are as basic and simple as gauges get, and decades ago were not uncommon. Unfortunately, hardly any drivers really understood them. I can’t remember the last time I saw a car with an ammeter (it was decades ago), and it seems only few cars nowadays that aren’t electric or hybrid have voltmeters.

36

this is appallingly ignorant and insulting.

No, it’s because the PCM is only able to give you a diagnostic trouble code (DTC) based on any out-of-spec parameters it detects. all a DTC tells you is where a problem is. It does not tell you what is wrong with the car. It’s like you going to a doctor with a sore shoulder. all you can tell your doctor is that your shoulder hurts and maybe what you were doing when it started to hurt. your doctor then has to do some diagnostic test to figure out if you have a torn rotator cuff, pinched nerve, torn cartilage, etc.

The industry standard indicator is a red “battery” icon. when that lights up, it means current is being discharged from the battery when it shouldn’t be. I highly, highly doubt your owner’s manual doesn’t say anything about that.

Here’s the thing. The symptom is that your “charging system is not working.” it doesn’t mean “your alternator is bad.” it could also mean “your accessory belt broke” or “the voltage regulator has failed” or “there’s a broken wire somewhere.” there’s no way for the car to know. So you (or a mechanic) still has to do diagnostic tests to figure out why the charging system isn’t working.

it’s not “thick headedness.” It’s because on-board diagnostics are not nearly as advanced and capable as you think they are.

37

ammeters were mostly used on cars back when they had DC generators, since the output of the generator depended heavily on engine speed, and could be spinning slowly enough to allow battery discharge under normal operating conditions. when alternators took over, they held the system at a relatively stable voltage and you should only ever see battery discharge if the system is overloaded or the alternator is not delivering current. in which case a simple light is enough; if the battery warning light comes on while you’re driving you’re in trouble.

38

This ↑↑↑ plus a good set of jumper cables. Anyone who doers not carry jumper cables deserves to sit beside the road for a few hours.

I am too cheap to actually rig a full dual battery system that is switchable so I just carry a cheap battery when traveling and keep it in the vehicle I use most the rest of the time.

Little cheap cigarette chargers will keep it topped up.

:cool:

40

reported

41

Just skimming over this thread, I did not see any reference to battery terminals corroding to the point where the car won’t start. The battery is not dead, but cannot be charged properly, and cannot discharge properly, because of the corrosion. In my experience, having a battery suddenly die is not that unusual, if the terminals are corroded. Clean the terminals, get a jump, and everything is good.