Car Battery

BlueonBlue

Goudy said:

cymruchris said:

Cloth_of_Gold said:

35har1old said:

Lorian said:

As above they often don't last past 5th/6th winter reliably.

Have had a car for 12 years same battery only 36000 on the clock

Our current car is 7 years old but has only done 20k miles and nowadays we only do about 1000  - 1500 miles per year, the vast majority of which are short, local journeys of about 2 - 4 miles each way. Our previous car was 13 years old when we replaced it and it had only done 50K miles. We've never had a battery problem with either but I wonder if we've just been lucky. I'm concerned now that we might have a problem this winter but on the other hand I don't particularly want to drive around nowhere in particular for 20 odd miles every week just to keep the battery topped up - especially as we live in a large city so driving is, frankly, a bit of a pain nowadays.

Different cars with different batteries consume different amounts of power when parked up. Some cars use a lot less/more than others - some cars can stand for weeks on end and start at the turn of the key - others can be left a week and be nearly as flat as a pancake. I happen to drive one of the latter, renowned for batteries being drained when not driven. I'm lucky that at the moment I have a garage, and can keep a top-up charger plugged in.

Yes, some modern cars these days tend to require a lot of electrical power even when parked up, but they tend to use far more power these days than they ever did in the past when running.

Most cars these days have some form of electrical power steering rather than hydraulic which is mechanically driven off the engine.
EPAS is usually big electric motor attached to the steering.
This tends to be really power hungry and when you add up all the other power demands on the battery, like repeated starting, heated screens and seats, lights and short tripping the car, it's a wonder batteries last so long.


Also modern cars tend to smart charge, ie the ECU decides what load the alternator puts out to recharge the battery.
This means it's the ECU programming that works out what is needed and if it's programming isn't conducive to lots of repeated short trips with high electrical load, chances are the battery will spiral down quicker.

Manufacturers don't really like fitting bigger batteries as that equals more weight which ruins emissions and mpg, so the battery will be adequate, just.

Now throw in a cold snap, as we know batteries don't like the cold (or too much heat) and the internets forums fill up with similar posts to this and when you are out and about you'll notice inconsiderate buggers have dumped their old batteries in the street.

If the OP hasn't dropped a clanger and left the lights on and the battery is acting like this now, you might save it and make it do a little while longer by using a charger to charge it back up and making sure to do trips above 8-10 miles to give the alternator the chance to recharge it, but chances are in a week or a month or two you'll be back in the same position.
 

When recharging the battery via running the engine you mention doing  8-10 mile trips .
If your parked at home or on the street what would the stationary engine running time be in minutes ?
Im guessing 20-30mins at least ?
 

Goudy

BlueonBlue said:

Goudy said:

cymruchris said:

Cloth_of_Gold said:

35har1old said:

Lorian said:

As above they often don't last past 5th/6th winter reliably.

Have had a car for 12 years same battery only 36000 on the clock

Our current car is 7 years old but has only done 20k miles and nowadays we only do about 1000  - 1500 miles per year, the vast majority of which are short, local journeys of about 2 - 4 miles each way. Our previous car was 13 years old when we replaced it and it had only done 50K miles. We've never had a battery problem with either but I wonder if we've just been lucky. I'm concerned now that we might have a problem this winter but on the other hand I don't particularly want to drive around nowhere in particular for 20 odd miles every week just to keep the battery topped up - especially as we live in a large city so driving is, frankly, a bit of a pain nowadays.

Different cars with different batteries consume different amounts of power when parked up. Some cars use a lot less/more than others - some cars can stand for weeks on end and start at the turn of the key - others can be left a week and be nearly as flat as a pancake. I happen to drive one of the latter, renowned for batteries being drained when not driven. I'm lucky that at the moment I have a garage, and can keep a top-up charger plugged in.

Yes, some modern cars these days tend to require a lot of electrical power even when parked up, but they tend to use far more power these days than they ever did in the past when running.

Most cars these days have some form of electrical power steering rather than hydraulic which is mechanically driven off the engine.
EPAS is usually big electric motor attached to the steering.
This tends to be really power hungry and when you add up all the other power demands on the battery, like repeated starting, heated screens and seats, lights and short tripping the car, it's a wonder batteries last so long.


Also modern cars tend to smart charge, ie the ECU decides what load the alternator puts out to recharge the battery.
This means it's the ECU programming that works out what is needed and if it's programming isn't conducive to lots of repeated short trips with high electrical load, chances are the battery will spiral down quicker.

Manufacturers don't really like fitting bigger batteries as that equals more weight which ruins emissions and mpg, so the battery will be adequate, just.

Now throw in a cold snap, as we know batteries don't like the cold (or too much heat) and the internets forums fill up with similar posts to this and when you are out and about you'll notice inconsiderate buggers have dumped their old batteries in the street.

If the OP hasn't dropped a clanger and left the lights on and the battery is acting like this now, you might save it and make it do a little while longer by using a charger to charge it back up and making sure to do trips above 8-10 miles to give the alternator the chance to recharge it, but chances are in a week or a month or two you'll be back in the same position.
 

When recharging the battery via running the engine you mention doing  8-10 mile trips .
If your parked at home or on the street what would the stationary engine running time be in minutes ?
Im guessing 20-30mins at least ?
 

It probably won't charge very well sat at idle.

Although alternators are more efficient and produce more power than old dynamos, what comes out of them is speed related. The slower they turn the less they produce. 

The alternator speed is dictated by the crank speed, the slower the crank speed the slower the alternator turns.

At idle the crank speed is 800-900 rpm.
Out on the road the engine runs much faster, up to 6500 rpm or more is possible but 2500-3500 rpm is around average on a cruise.

So on that average the alternator would spin something like 3.5 times or more slowly at idle than out on the road, which means it would put out far less at idle than out driving.

You also need to think about modern cars with smart charging systems.
They vary the alternator output depending on load.
It's would be wise to spin the alternator up on the over run (when you release the accelerator) as it would save on fuel rather than loading the engine up to spin the alternator up when you accelerate.
So it's likely at idle the alternator isn't producing much power at then either.

You also need to factor in some of the emission and mpg tests that get performed on cars.

Perhaps not as scandalous as VW's "cheating" their emissions test, but it's not beyond imagination that the smart charging programming it set to perhaps lighten the alternator load on the engine at certain test speeds to help improve those figures, again that would likely be lower engine speeds.

sevenhills

Goudy said:

Although alternators are more efficient and produce more power than old dynamos, what comes out of them is speed related. The slower they turn the less they produce.

I put a new battery on my Zafira and I am still having problems. The voltage was 13.5 with the engine running at tickover, it does increase, but with the lights and blower on it does drop below 13.5v

I often only use it 2/3 times per week, short journies, its not coping. I have had to charge the battery a couple of times.

Brewer21

Get one of these tools below, always handy to have in the toolbox.
A while back my battery went low, my fault as I was tinkering with the electric windows, too much drawn from the battery. I had a fault light appear on the dash when I next drove the car. I hooked up the analyser and it said the battery is good just needs charging. On my other car it told me the battery was ok but wouldn't hold a charge, needs changing. That was true, as I'd just ordered a new one to replace the 8 year old battery.
Also invest in a smart charger if your car sits a few days without use. Better to keep them up in good nick than deteriorate prematurely.

https://www.ebay.co.uk/itm/372436652444?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=vrAwd99DT4i&sssrc=4429486&ssuid=PjrX0wOKTfG&var=&widget_ver=artemis&media=COPY

Arunmor

Covid did for us a few batteries through lack of use, I guess the ones that saw it through those times are now struggling a bit.

A top tip if you are changing the battery yourself and if necessary coding it, you may end up with every light on the dashboard on.  Don't worry just drive it a couple of hundred yards and they should all go out.

Goudy

sevenhills said:

Goudy said:

Although alternators are more efficient and produce more power than old dynamos, what comes out of them is speed related. The slower they turn the less they produce.

I put a new battery on my Zafira and I am still having problems. The voltage was 13.5 with the engine running at tickover, it does increase, but with the lights and blower on it does drop below 13.5v

I often only use it 2/3 times per week, short journies, its not coping. I have had to charge the battery a couple of times.

How are you measuring the voltage, with a multimeter at the battery terminals?

General rule of thumb is:

1. With the engine off and all electrical items on the car off (resting voltage), you should see around mid to high 12's, give or take a few decimal points. (I'd be happy with 12.4 to 12.6v)

2. With the engine running and all electrical items off, I would expect to see 13.8 to 14+v . (I'd be happy seeing 14.4v)

3. With it running still, if you get someone to quickly switch on the high beam and the heated rear window together while you are still reading the volts at the battery.
The volts may drop a little but the alternator should up it's game quite quickly to compensate and start heading back towards the reading high 13's to 14+v again.
You might hear the load on the alternator change the engine tone a little as the alternator starts working harder.

So your 13.5v when running looks a little low.
Is the Aux Belt that turns the alternator old, stretched and slipping?

Goudy

Reading volts is only half the equation though.
Car batteries need plenty of amps and they are harder to test.

With a multimeter you can test the volts easily, but try hooking one up set to amps (don't try it)
It's fry meter and burn the wires in the probes!

There are specific tools to test a battery for amps, the old tool was a drop tester.
It used to be called a battery drop test (no, don't throw it out the bedroom window)
That test basically applied a load across all the cells but these days there are better tools to do the same thing.

And yes, it's possible for a car battery to have plenty of volts but too little amps.

 

Veteransaver

How did Halfords check it exactly? If they just measured the voltage at the terminals then this is meaningless as it had just been driven.
If you have a voltmeter you can do a simple check yourself though. Leave the car for several hours and measure the battery voltage. If it's below about 12.3V it could indicate it's on its last legs.
If you have a charger then you could charge it (divide the Amps of the battery by the Amps of the charger and add a couple of hours) Eg if it's a 40Amp battery and a 5Amp charger, charge it for 40/5 = 8hours, plus a couple of hours.
Take it off charge and leave it for several hours. If the voltage isn't above 12.5V it's probably had it.

EnPointe

Cloth_of_Gold said:

35har1old said:

Lorian said:

As above they often don't last past 5th/6th winter reliably.

Have had a car for 12 years same battery only 36000 on the clock

Our current car is 7 years old but has only done 20k miles and nowadays we only do about 1000  - 1500 miles per year, the vast majority of which are short, local journeys of about 2 - 4 miles each way. Our previous car was 13 years old when we replaced it and it had only done 50K miles. We've never had a battery problem with either but I wonder if we've just been lucky. I'm concerned now that we might have a problem this winter but on the other hand I don't particularly want to drive around nowhere in particular for 20 odd miles every week just to keep the battery topped up - especially as we live in a large city so driving is, frankly, a bit of a pain nowadays.

where is the vehicle parked ? if you have a drive or garage you could consider  a 'battery conditioner'  trickle charge  unit  assuming you can safely run a  mains cable  betwixt a  socket and the vehicle ... 

I used to use some specialist  vehicles which despite supposedly having isolators had an issue with quiesence drain  - this was solved by  fitting a battery conditioner   and plugging into the mains if the vehicle was going to be left  for  a numbers of days / weeks  without being used

sevenhills

Goudy said:

How are you measuring the voltage, with a multimeter at the battery terminals?

So your 13.5v when running looks a little low.
Is the Aux Belt that turns the alternator old, stretched and slipping?

I have a voltmeter that plugs into the cigarette lighter, I have also measured it with a multimeter.

When driving, it reaches 14v, 13.5v when the lights etc are on, which to me indicates that the alternator is charging ok.

But something is wrong.