Cranking Battery Power

Submitted: Sunday, Mar 30, 2008 at 20:00
ThreadID: 56087 Views:2139 Replies:18 FollowUps:20
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At what voltage would a cranking battery be considered flat?

My Century Overlander now 3.5 years of age has been letting me down of late. If the vehicle stands for a day or two the battery won't crank the motor.

My auxilliary battery is 4.5 years of age. Joined the two up today with jumper leads but to no avail.

Battery terminals are secure but I haven't cleaned them in a while. They are not showing any acid build-up though. Maybe I should do that!


Cheers

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Reply By: Notso - Sunday, Mar 30, 2008 at 20:08

Sunday, Mar 30, 2008 at 20:08
Either the battery is shot or there is a leakage of power somewhere.

AnswerID: 295660

Follow Up By: Willem - Sunday, Mar 30, 2008 at 20:33

Sunday, Mar 30, 2008 at 20:33
Yes and Yes but if there is a leakge I don't know where, 'cos I have looked at every possible connection and pilot light, and all seems secure.
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Reply By: Member - JohnR (Vic)&Kath - Sunday, Mar 30, 2008 at 20:11

Sunday, Mar 30, 2008 at 20:11
So will you change them before you go into the desert?
Cheers,
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Follow Up By: Willem - Sunday, Mar 30, 2008 at 20:27

Sunday, Mar 30, 2008 at 20:27
Dunno about the desert now. Run into officious bureaucrat.

Will have to get battery though...lol
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Reply By: Jim from Best Off Road - Sunday, Mar 30, 2008 at 20:17

Sunday, Mar 30, 2008 at 20:17
Willie,

According to the research I have done, a standing voltage of 10.5 is flatter than my nose.

3.5 years from a quality battery seems a little ordinary to me. Anyway, we can discuss such issiues over a drop of.......

See you later in the week.

Jimbo

AnswerID: 295663

Follow Up By: Willem - Sunday, Mar 30, 2008 at 20:26

Sunday, Mar 30, 2008 at 20:26
Yup...will do that.

Reading was showing 12.3.

Maybe there is something loose somewhere....lol


Cheers
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Reply By: Member - Axle - Sunday, Mar 30, 2008 at 20:20

Sunday, Mar 30, 2008 at 20:20
Mate, !! Me thinks it a case of old age all round!..hahaha.


Cheers Axle.

AnswerID: 295666

Follow Up By: Willem - Sunday, Mar 30, 2008 at 20:24

Sunday, Mar 30, 2008 at 20:24
Hahahahaha....cheeky young fella


Cheers
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Reply By: Member - Kiwi Kia - Sunday, Mar 30, 2008 at 20:31

Sunday, Mar 30, 2008 at 20:31
Aprox % levels of charge

100% = 12.7V
75% = 12.5V
50% = 12.2V
Discharged = 11.9V
AnswerID: 295670

Follow Up By: Willem - Sunday, Mar 30, 2008 at 20:35

Sunday, Mar 30, 2008 at 20:35
Thanks.

Voltage shows at 12.3V. Could be a crook Multimeter....lol
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FollowupID: 561687

Follow Up By: Member - SNAKE (RAOUL) QLD - Sunday, Mar 30, 2008 at 23:14

Sunday, Mar 30, 2008 at 23:14
Willem, Who writes your lines?Nearly hissed re the crook multimeter.Cheers Snake
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Reply By: mechpete - Sunday, Mar 30, 2008 at 20:40

Sunday, Mar 30, 2008 at 20:40
bye ya self 2 new batteries , these days if ya get 2or 3 yrs out of them ya doin well , remember the cold weather is here an that will catch you out , ( ps the only way to check a battery is to test it under full load ) standing voltage means nothing
mechpete
AnswerID: 295675

Follow Up By: Willem - Sunday, Mar 30, 2008 at 20:51

Sunday, Mar 30, 2008 at 20:51
Thanks Pete

Thats probably what it is. After our heatwave we are now wearing sox and overcoats

Next payday maybe. $300+ for 2 batteries...almost as bad as the fuel price...lol


Cheers
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Follow Up By: Member - Kiwi Kia - Sunday, Mar 30, 2008 at 21:46

Sunday, Mar 30, 2008 at 21:46
As mechpete says William, check voltage under load. Turn the headlights on and measure the voltage at the same time.

What is actually happening when you try to start ? Do you get any engine turnover at all ?
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Reply By: Member - Mike DID - Sunday, Mar 30, 2008 at 20:48

Sunday, Mar 30, 2008 at 20:48
For a battery voltage to give you an indication of state of charge, you have to wait several hours after stopping ALL charging or discharging - including the Interior Light.

12.3 volts should be enough to start the car - provided the battery has not deteriorated internally is really only a 10 amphour battery.

You may have black corrosion on the positive terminal - very hard to detect. Remove the clamps and clean the posts with emery paper until you see bright metal.
AnswerID: 295678

Follow Up By: Willem - Sunday, Mar 30, 2008 at 20:55

Sunday, Mar 30, 2008 at 20:55
Thanks Mike

I charged the battery for 4 hours and it kicked over no worries. Will still clean the terminals though.
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Reply By: Member - Phil G (SA) - Sunday, Mar 30, 2008 at 20:49

Sunday, Mar 30, 2008 at 20:49
Willem,
12.3v after a couple of days means the battery is getting drained, or you haven't been driving enough to charge it right up.

Check the voltage while the motor is running and the glow plugs are no longer glowing - should be about 14.0V, which tells you the alternator/regulator is fine.

If thats OK, hook a 10amp ammeter up to one of the terminals, and work out how much current you are losing when everything is turned off. Should only be a fraction of an amp.
AnswerID: 295681

Follow Up By: Willem - Sunday, Mar 30, 2008 at 20:58

Sunday, Mar 30, 2008 at 20:58
Ta Phil

I do too many short runs, I think. Although I did a run to PA on Friday. Is charging at 14V...new bloomin' alternator!

Whats an Ammeter?

BTW Fitzy had a look at my brake/rotor/bearing problem and declared it fit and well. Now I don't know!!!!!.....lol


Cheers
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Follow Up By: Member - Phil G (SA) - Sunday, Mar 30, 2008 at 21:20

Sunday, Mar 30, 2008 at 21:20
Glad you got Fitzy to look at the front end. When it comes to 4wds, he knows it all. My hubs get hot too, I don't believe that you have a problem.

Ammeter measures current. Most digital multimeters can measure up to 10amps, but you need to move the red lead to a different socket to make the measurement. Simplest way is with the motor stopped, to loosen the neg terminal on the battery, one probe on the battery post, the other probe on the terminal, and then remove the terminal to make the measurement. Any current being drawn will flow thru the multimeter and be measured. If its more than about 100milliamps, then its too much.

I'd guess that your problem is too many short trips. Mine sits in the shed for weeks at a time, but rarely drops below 12.6V, but I put it on a charger anyway.
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FollowupID: 561707

Follow Up By: equinox - Sunday, Mar 30, 2008 at 21:48

Sunday, Mar 30, 2008 at 21:48
Whatever you do, don't connect the multimeter directly across the battery terminals when it is set to AMPS.
Looking for adventure.
In whatever comes our way.

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Reply By: Robin Miller - Sunday, Mar 30, 2008 at 20:59

Sunday, Mar 30, 2008 at 20:59
To answer your question Willem, a healthy battery in a low state of charge will start car from about 11.0 volts upward.


Robin Miller

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Follow Up By: Willem - Sunday, Mar 30, 2008 at 21:02

Sunday, Mar 30, 2008 at 21:02
Thanks Robin, but what constitutes a healthy battery?
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Follow Up By: Robin Miller - Sunday, Mar 30, 2008 at 21:10

Sunday, Mar 30, 2008 at 21:10
I don't mean this to sound cute - but a battery that will restart the car at 11.0v is healthy.
If it doesn't it means its getting sulphated up or has other faults that rasies its internal resistance.

As a post further up says Willem , its under a load that really counts.
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Follow Up By: Member - Phil G (SA) - Sunday, Mar 30, 2008 at 21:27

Sunday, Mar 30, 2008 at 21:27
Robin,
I'd believe you'd have a chance of starting a petrol motor at 11.0v, but an old fashioned diesel usually pulls about 60amps from the glow plugs before they need the big amps to crank a high compression motor.

I've only tested mine down to 12.15V and it did start easily. But I've been unable to start a LandRover TD5 at 12.2V (battery was allegedly in good nick).
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Follow Up By: Robin Miller - Monday, Mar 31, 2008 at 07:58

Monday, Mar 31, 2008 at 07:58
Hi Phil

Certainly harder all right , but problem might be that 11.0v is getting pretty low and those glow plugs could as you suggest hurt the remaining charge and make it to hard.

But the battery internal resistance doesn't change a lot and it can generate the peak amps.
Have a bad habit of to often starting my car at 11v and current supplied still reads around 400 peak amps.

The battery of course it couldn't supply that for much for even 30 seconds.

But I take your point that it is a bit dependant on the car, there is a wide variation, and older diesel in particular can be harder and take longer.
Some diesels like the Patrol 3lt with 16:1 draw much the same current as my 4.8 10:1 petrol.

Modern petrols keep the spark voltage constant and fuel pressure up and mine only takes under 3 seconds (hence a claim I have made that I have started car with pack of AA cells , first discharged into battery).

Soon I hope to trial a Li-ion , which is now available for bikes with starter motors (12V 4ah about a 1kg i think)







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Reply By: Star Bug - Sunday, Mar 30, 2008 at 21:12

Sunday, Mar 30, 2008 at 21:12
Was told by a auto lec once. Check the terminal voltage while cranking. If it drops to 11v or was it 10.5v, time to consider a new one.

AnswerID: 295692

Reply By: Derek from Affordable Batteries & Radiators - Sunday, Mar 30, 2008 at 21:16

Sunday, Mar 30, 2008 at 21:16
Do a hydrometer test on the cells.

Also what is the voltage while trying to crank. If it drops below 9.5V while cranking or trying to crank there is no capacity in the battery or it has a dead cell.

Your auxiliary battery could also be on its way out. Try get them both load tested.
AnswerID: 295694

Follow Up By: Derek from Affordable Batteries & Radiators - Sunday, Mar 30, 2008 at 21:27

Sunday, Mar 30, 2008 at 21:27


Load test chart.
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Follow Up By: Willem - Monday, Mar 31, 2008 at 09:16

Monday, Mar 31, 2008 at 09:16
Thanks for the chart, Derek. Your imput is always appreciated



Cheers
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Reply By: Isuzumu - Sunday, Mar 30, 2008 at 21:41

Sunday, Mar 30, 2008 at 21:41
Have it tested so as can show what cranking amps its putting out.
If the battery is say an 900 cranking amp batery and the tester come up with 400 than the thing is stuffed ok
Cheers Bruce
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AnswerID: 295702

Reply By: mechpete - Sunday, Mar 30, 2008 at 22:03

Sunday, Mar 30, 2008 at 22:03
what I mean by under load is if the battery is rated at 600cca!! ,then you check it at that load for a mininum of 15 secs and what the votage it should not drop below about 11.5 or 12volts .
mechpete there is a load tester to do that .
AnswerID: 295710

Reply By: Richard Kovac - Sunday, Mar 30, 2008 at 22:04

Sunday, Mar 30, 2008 at 22:04
Hi Willem,,
You and me together, my 1.5 year old Century Overlander N70ZZH just craped itself it has dropped a cell ... 5 in the green and one in the black showing 12.5 volts on the multi meter.

but can not start the Troopy, started to happen around a month ago, but because the Troopy is the second car now blamed it on not using it.

what it shows on a volt meter when doing nothing means only that (what it stores) like a water tank, but if it does not have enough pressure (volts) when needed it wont start the motor.

A fully charged battery should only drop it charged state by around 10% eg. 12.5 - 11.25 volts, to check this put your multi meter on the battery in front of the bonnet so you can see it and crank the batter(mine drooped to 6.5 volts then i checked it with a hydrometer)

I should check mine more often or get them load tested..

I hope this makes sense
AnswerID: 295711

Follow Up By: Richard Kovac - Sunday, Mar 30, 2008 at 22:12

Sunday, Mar 30, 2008 at 22:12
The worse part is that the aux battery was low as I have not had the solar system hooked up to it as the Troopy is due a service and now has sat around for a week, and it can't start the dam thing, I've now got it out there on charge just so I can get the thing going. I did not swear to much.. LOL

Cheers

Richard
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FollowupID: 561726

Reply By: MrBitchi (QLD) - Monday, Mar 31, 2008 at 09:00

Monday, Mar 31, 2008 at 09:00
"At what voltage would a cranking battery be considered flat?"

At whatever it reads when it won't start ya car ;-)
AnswerID: 295748

Follow Up By: Willem - Monday, Mar 31, 2008 at 09:12

Monday, Mar 31, 2008 at 09:12
Yes John...and that seems to be 12.3V.....lol


Cheers
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FollowupID: 561765

Reply By: Willem - Monday, Mar 31, 2008 at 09:15

Monday, Mar 31, 2008 at 09:15
Thanks everyone for all your diverse comments and suggestions.

It is always good to tap the forum so that the old forgotten stuff in the grey matter can be revitalised.

Either way, I am up for new batteries.....LOL


Cheers
AnswerID: 295751

Reply By: traveller2 - Monday, Mar 31, 2008 at 10:45

Monday, Mar 31, 2008 at 10:45
Willem
while you are cleaning things remove and clean the chassis or engine end of the earth/ground cable. Take the metal back to clean and shiny, then reaffix soundly.
Also check both end of any other earth cables between chassi and engine and chassi and body.
It is amazing how brighter the lights are when you clean ALL the connections especially on older vehicles.

Peter
AnswerID: 295763

Reply By: Member - Davoe (Yalgoo) - Monday, Mar 31, 2008 at 13:10

Monday, Mar 31, 2008 at 13:10
batterys are like tyres. even though you pay a fair bit for them they are just a disposeable item. Once they wont holsd charge they are stuffed and need to be binned. last stuffed battery i bothered to put a MM on showed 12.3V
Bin it and get a newie. at that age it shouldnt be trusted for remote trips anyway
AnswerID: 295769

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