SOT: car battery question

I've had batteries fail suddenly a couple of times. Many years ago, one started normally, we drove for 20 minutes, parked up to see the storm waves and when we tried to re-start, there was not enough to even try to turn the engine. Two cells had suddenly failed. Not fun on a rural coast, miles from anywhere, on New Year's eve!

Two and a half months ago, another started, took us 35 miles, restarted,

Yup.

I was getting weird codes and got my battery tested. They said it was about half what it should have been, It always started though. I replaced it. Cant be arsed with dead batteries on a cold morning. I would say a new battery every 5 years is the safest way to go

In both of my cases, there were no signs at all - no codes, no warning lamps, engine turning over and starting with its normal sound/speed. Just working fine and then not.

I don't have any proof this is true, but there is a claim that the acid in the battery (normally

This reduces the effective plate area of the battery, and it has fewer cold cranking amps. Only the lower part of the plate, has the amperes.

While some mechanics in he past, have put the battery on their big charger and "boiled the s*it out of it", that's not a good idea from a Health and Safety perspective.

Now, if this description has any hint of reality to it, then it's a question of cart versus horse. Which came first ? Did the plate packing fail on the upper part of the plate, such that the upper part of the plate could not take a charge ? Or, did the acid stratify out of spite, dooming the fully functional plate, to uneven performance over its height ? Dunno.

But the symptoms seem to be, abnormal charging behavior. It "fills faster than normal" and it is gutless, until it leaves you stuck under seemingly rather benign conditions. It might not be very cold, when the engine won't turn over, and the temperature under the hood might have warmed the battery enough to be "ideal for starting". Yet, there is nothing left.

If anyone is keeping track, you might notice the battery life is getting shorter and shorter. And that's a rent seeking behavior of the battery industry. They can actually make automotive batteries that last seven years. They know how to do that.

My last UPS battery, three of the cells failed short. That's not normal either. The charging characteristic (I left the cover off and checked with a meter), does not seem defective. Even the original battery was Chinese, but the original worked a lot better than the replacements.

Paul

I was once told by a recovery technician that the terminal posts on some batteries were just a press fit on the gubbins underneath when the top of the battery was put in place, and sometimes just failed with ‘dead battery’ symptoms or didn’t supply enough volts when the starter was actuated.

I'm not sure if it happens on AGM style batteries but older batteries readily would shed lead particles from the plates. Over time a layer builds up at the bottom of the case and eventually it can be deep enough it shorts out the plates in the cell. A fix is to drain the acid and flush the crap put and fill with fresh acid.

Or buy a new one.

Far be it from me to suggest that battery makers started reducing the gap between the bottom of the plates and the case in order for batteries to fail sooner. But normally just past the end of the warranty.

Anyway I have seen this sudden failure twice in recent years on my wife's cars. Each time it was fine and the turnover sounded healthy until "click" nothing. The last time I heard her start the car and drive off and return later. Next morning, nothing. My 45 years of driving has me used to the performance tailing off not sudden death.

A few months ago my car battery was as dead as a dodo, down to five volts IIRC. Admittedly it had been standing in the garage for a week or ten days, but I didn't think a car battery could get that low in such short a time. I assume there's a trickle-drain taking place, presumably running some electrics somewhere, even when everything is nominally 'off'. Not come across that before.

Whatever, I now give it a charge for an hour every Sunday morning, although it usually reaches maximum capacity after half that time.

Where did you see that? It's about 30% acid, equivalent to 4.2 - 5M.

This wasn't a high resistance connection, the batteries had gone from starting the car normally to a no-load voltage of 8 and a bit volts.

My battery may not have been the reason for the codes, but taking it into a battery centre to get it tested revealed that what appeared to be a perfectly sound battery had about double the internal resistance it should have had, and that is the first sign...

In general my lawnmower battery lasts about 5 years I don't expect my cars' batteries to last longer than that.

Oh, and other thought strikes. I was living next to a building site. One day the bloke asked me to jump his car.

I did, and didn't lock the car., The next day the battery was dead. I don't think it was the same battery in the car any more...

Radio and security alarm both draw power - even with the ignition off.

As it turns out, the freezing point depression isn't a reliable indicator of molality in this case.

If we take a -50 data point off the graph, that's about

But I did have a Panasonic sealed battery for automotive, that lasted for seven years. It is possible to make a good battery.

Paul

Before we had intelligent cars, a "leak" was 20-30mA and not something that would cause an overnight disaster.

But in at least one case, the audio system left a 5 ampere load on battery, which will have more of an impact on your morning drive.

The alternator and voltage regulator on modern cars, don't seem to charge batteries as aggressively as they used to. This cannot be helping things. There have been plenty of complaints from owners of modern cars, of the starter battery being kept at an abnormally low level of charge. The owners finding, that if they manually charge their car on a regular basis, they have fewer "morning surprises". But you should not have to do that, if the design was half decent. The battery would accept the charge, if it was given the charge to work with.

Paul

But should be low enough to give around 3 weeks non-use without problem.

The Bosch battery that I fitted to my Astra H 1.6 petrol in November 2015 was still going strong when I sold the car a couple of months ago.

Just buy quality batteries.

During lockdown(s) I had to call the AA out twice because my battery had gone flat during periods of low, or no, use. After the second time I got a solar trickle charger

If it's amodern car, then yes, they do always have some discharge when parked, to maintain various things, alarms, radio stations, the engine ECU. Mine discharges at constant 20 - 25mA, so would flatten the battery within perhaps 4 weeks. Some cars, switch things off, after a few days of none use, to help preserve the battery. The regular discharge, then recharge cycle is not good for batteries, especially if it's parked up for a few days at a time, like mine.

My workaround, is to have it connected to a dumb charger, in my garage, which comes on for twenty minutes each day, to make up for the discharge.

There have also been software bugs, mostly in entertainment equipment, that have cause significant drains and flattened the battery quickly. A malfunctioning Bluetooth seems to be a common issue.

Or hardware:

"Second, get a proper diagnostic check done by someone who KNOWS what they are talking about. You have been ripped off. The most common fault on these cars is a fault code of P0340, camshaft sensor circuit fault. THIS DRAINS THE BATTERY OVERNIGHT. It is a well known and documented fault which any decent garage and every Renault dealer knows about."

'Parasitic battery drain' will turn up many pages on Google.

Note that disconnecting the battery for testing or replacement can have issues. I know someone who changed the battery on a Renault without performing the proper dead chicken rite first, and killed the ECU. For that particular model there was an entirely unintuitive routine which involved at one stage turning off the ignition with all doors closed, while reaching in through the open driver's window.

I went to collect my grandsons from school. The car had been used that morning and was happy getting us there.

Once the kids were seated and belted, it wouldn't start. I called Green Flag. The engineer took a while to identify a flat battery. The reason was that the only panel icon that illuminated was for the airbags.

He said that modern cars are rubbish. He told me to buy a replacement battery but get a good one.

I had expected to fit it myself. I have in the past. When it came to it, nothing in my socket sets could reach down to the securing bracket. I called my local garage. They were brilliant. Nothing is too much trouble and they never take liberties. A tenner changed hands. Job done.