How to test a dead car battery & not just a flat one?

JustAnotherSaver

Well it did drop. Went from 12.45 to 12.25.

Put it back on charge overnight as she needed it & tested it all again and it did the same again. 12.45, down to 12.25 some time later & then 12v or possibly like 11.95v, can't remember now - a bit later.

Had a Halfrauds voucher from work so basically picked up a new 4yr one for £20 once my trade card had been used.

Just annoying that I can't find the receipt for the duff battery.

JustAnotherSaver

Wondering if any knowledgeable folk can shed some light on this as I've just been done by the Halfrauds computer says no.

So little recap:

Old battery -

* in use daily or fairly close to daily. Not shown any signs of trouble. Car sat on drive then for 3 days and wont start the car - 8.7v or whatever I said it was. Under 9v at any rate.

* Put it on charge for around 40hr. Start it up & upon startup it's showing 14.4v. Engine off and IIRC it was somewhere around the 12.6v - no problem.

* Out on a little drive, come back, test throughout the day & it drops to 12.45v then down to 12.25v.

* Stick it on another overnight charge as car is needed next morning. Once car is back I test it throughout the day. Same as before .... 12.60v....12.45v....12.25v and then finally on down to whatever it was, somewhere around 12.00v +/- 0.05v.

A note on the initial huge drop:

The only thing I can think of that stays on without keys is the headlights, but then these make a ding ding ding noise at you when you open the door & they're on, so you can't really leave them on (well you can, but you'd have to actively choose to ignore the warning noise & then you're just an idiot).

Everything else turns off with the key. Radio, fans, dash cam, interior light.

Then buy a new battery.

* Install it and literally no problems - constant 12.60v just sitting there. It's been sat for 15-18hours now, gone through a chilly night & just tested it again - 12.60v. No drop whatsoever.

Take the old battery to Halfrauds & as I suspected - their test says it's a perfectly good battery.

At this point the guy clearly didn't give a toss, not that I expected him to tbh. He was the same guy who served me the new battery so I just explained how that is holding charge no bother & this one keeps dropping. Leave it long enough and it doesn't start the car etc etc so on & so forth.

Just shrugs & says tester says it's good.

(Now as I'm no car or electrical expert .....) I ask what it could be then to explain that this battery wont hold charge but the brand new one does (basically I'm saying it's the battery at fault, not the car - as the same would surely happen to the new battery if it was the car?).

Guy just says could be anything. Cold weather, anything.

Well no as it was dropping while the weather was actually quite warm but I was fighting a no-win battle so I knocked it on the head & left.

Got the multimeter back out when I got back - annoyingly the old battery showing 12.50v. Well, actually the reading flashed up 19v at first but then when I took the probes off & put back on it showed 12.50v.

What gives?

For ref: The battery is a Halfords HCB075.

Jenni_D

Obvious question alert - did you make sure the new battery was fully charged before/after fitting it?

Have you tried the ammeter test as described earlier in this thread? (To see how much current is actually being drawn rather than guessing at what might be causing a draw)

[Deleted User]

JustAnotherSaver said:

Take the old battery to Halfrauds & as I suspected - their test says it's a perfectly good battery.

The test doesn't say perfectly good battery, it says that when a conductance test was executed it indicated that the internal resistance of the battery was such that it could achieve 506 amps on a CCA test. 

At no time was the battery ever subject to a 506 amps discharge on the handheld tester used by Halfords. It was simply estimated based on internal resistance. It was one of many tests that should be carried out, the results alone are not the indicative of a healthy battery without context of other test results.

Note that a proper CCA test was not carried out, if it was it would have failed due to the state of charge of the battery. Proper CCA tests are more fun but I rarely see them being done nowadays, lots of sparks and red hot glowing metal but I guess they are too dangerous for a Haflords employee to do.

The results said re-charge the battery. You have done that already and it failed to hold charge for one of two reasons:

1. Parasitic drain from the car at standby - a test for this was suggested in a few previous comments but I can't see any results of that so we will never know whether that was the cause. Not only is that a really easy and simple test given you have a multimeter, it would have given a more definitive conclusion if you had done it.

2. The battery is failing to hold charge due to reaching the end of serviceable life, typical causes such as lead shedding through corrosion can cause a "soft short" internally which will discharge the battery over time but won't fail a CCA test such as the one that Halford performed. Sulphation and acid stratification are two other causes of failure that might still pass an internal conductivity test.

I've eliminated the third reason of the alternator not recharging the battery based on results from previous comments - eg the 14.4v charging voltage and the battery dropping voltage when the car was not in use.

JustAnotherSaver said:

Got the multimeter back out when I got back - annoyingly the old battery showing 12.50v. Well, actually the reading flashed up 19v at first but then when I took the probes off & put back on it showed 12.50v.

What gives?

I did say on an earlier post "depending on the accuracy of your multimeter" and maybe there is some doubt as to the accuracy now it showed 19V and 12.5v instead of the 12.28v when tested by Halfords, but putting that aside, the fact the battery has been removed from the car and sloshed around, change of temperature etc might give some variation in voltage.

Anyway if you are determined to find out if the old battery is good or not, then fully recharge it using your Ctek charged, including the recondition cycle and monitor the voltage daily for a few days to see what happens.

Lead acid batteries can fail in so many different ways that 1 type of test alone is not enough to determine the state of the battery.

JustAnotherSaver

Jenni_D said:

Obvious question alert - did you make sure the new battery was fully charged before/after fitting it?

Have you tried the ammeter test as described earlier in this thread? (To see how much current is actually being drawn rather than guessing at what might be causing a draw)

* Aside from just chucking the new battery in, I stuck the multimeter on to see what it was reading - 12.60v. Actually come to think of it, I think it was 12.70v before I installed it.

* No I'm afraid I haven't. You're talking about this link: https://www.wikihow.com/Find-a-Parasitic-Battery-Drain right?

Although perhaps a stupid question - if there was something going on to cause a draw on the battery, surely it would draw on every battery that's fitted and not just that particular one?

As the new battery remains at a constant 12.60v - which the old one couldn't.

[Deleted User]

JustAnotherSaver said:

Although perhaps a stupid question - if there was something going on to cause a draw on the battery, surely it would draw on every battery that's fitted and not just that particular one?

As the new battery remains at a constant 12.60v - which the old one couldn't.

It’s not a stupid question and your assumption is probably right but the parasitic drain test is so quick and simple to do it isn’t worth assuming anything. 

Most modern cars do have battery drain protection so anything you would typically leave switched on would be switched off after a period of time or give a warning when exiting the car, but something going faulty might still drain the battery without any obvious malfunctions.

It could be that drain on the battery is intermittent and just so happens that it isn't doing it now you have put your new battery in. It could be that something was left switched on which is now off since the new battery was fitted - eg an interior light or the parking lights on one side of the car from leaving the indicator on.

It was the 8.7v from the old battery that strongly suggested something had drained it unexpectedly and continuously. Sorry to bang on about it but that is why the drain test was so important, it would have ruled that in or out as a cause.

If parasitic drain was definitely ruled out, it would pointed towards a soft short in the battery due to shedding lead, sulphate build up or failure of the insulated separators.

If it was sulphate build up, that can be tackled with a Ctek charger in reconditioning mode - it sounds like you pulled the plug on the charger in that mode so we don't know how long it has attempted reconditioning and whether it might have saved the battery. You will need to full charge again and let it complete the recondition cycle to see if that works.

Once that battery was manhandled out of the car and banged around a bit you may well have changed to characteristics of the fault - the acid will have been stirred up and the plates will have taking a bit of banging. A dangerous and outdated method of reconditioning lead acid batteries is to drop them from a height of about 6 inches which can knock sulphate deposits from the lead plates.

A bit more patience might have saved you changing the battery right now and given a bit longer life, but in fairness if you want your car to be reliable then once the battery is showing signs of weakness it is best just to get a new one.

JustAnotherSaver

Thanks for the detailed response. Very helpful.

After a chat with the wife (her car) she said she'd just feel better with a new battery since the last one has a 4year guarantee and it's damn near 4 years.

I pointed out that I've just changed the battery on my own car which was, at the very very youngest it could possibly be, was about 7 years old. It could've been 9 or 10 years old, so for hers to 'fail' just shy of 4 when it's marked as a 4 year battery - not impossible but I would've been very surprised that it's suddenly of no use.

But we have no plans to get rid of the car. It's a 15 year old car and nothing special at that (so basically it's worthless in terms of money value). It is however fairly reliable. The next one may not be. So as it's staying she decided to just get a new one put on (plus I had a voucher from work that could be used at Halfrauds, plus I had my trade card so the battery cost me £20).

Just very disappointed in their guarantee/battery check.

I think in future, unless Halfrauds are exceptionally cheap I'll buy elsewhere.

face-t

YOu have some solid advice above.

What I know about car LEAD batteries, is: once they are flat they are almost not possible to recondition and use again, hence you were given idea to drop the battery from height to shake off deposits. But then you will not know did it work or not and also lead panels might be worn anyway.

To make lead batteries to live longer - it is good idea to use trickle charger. I bought one from discount market at around £11 and use it before winter and mid winter, but theoretically you can use it every day.

JustAnotherSaver

face-t said:

LEAD batteries,

Does this apply to calcium batteries also as the one in this post?

https://www.halfords.com/motoring/batteries/car-batteries/halfords-hcb075-calcium-12v-car-battery-4-year-guarantee-950600.html

[Deleted User]

JustAnotherSaver said:

face-t said:

LEAD batteries,

Does this apply to calcium batteries also as the one in this post?

https://www.halfords.com/motoring/batteries/car-batteries/halfords-hcb075-calcium-12v-car-battery-4-year-guarantee-950600.html

Calcium batteries are just a variant of lead acid.

Traditional lead acid batteries use antinomy to strengthen the lead plates, calcium batteries use calcium. It accounts for less than 1% of the materials in the battery so isn't significant but does change the characteristics a bit.

Calcium batteries can tolerate a higher charge voltage and should be a bit more durable but can also suffer increased sulphation on the plates if not kept fully charged.