Battery let me down

[John B]

I've noticed over the last few days my terrano is struggling to start and the battery is 21 months old. Could anyone tell me what reading I should be getting on the battery when the engine is running to see if it's the alternator which is giving me the problem ?? Cheers again

 

[Banshee]

I've noticed over the last few days my terrano is struggling to start and the battery is 21 months old. Could anyone tell me what reading I should be getting on the battery when the engine is running to see if it's the alternator which is giving me the problem ?? Cheers again

Engine off - 11-12v

Engine on - 12-14v

 

[Banshee]

Pop to Halfords and get a drop test done on it tomorrow for nothing :thumb2

That will be the ultimate test as it will tell you if it's holding charge right, it could appear to be holding charge but may have faulty cell that's not holding it's charge

 

[solarman216]

good battery off load should read 12.8 volts engine running should be 14.2 ish, but this is no guide to the batteries capacity, the best way of determining this is with a high amp discharge meter, not many garages bother with these any more, preferring computer crap instead but they do not place a good load on the battery so the results dubious, Rick

 

[rustic]

Engine off - 11-12v
Engine on - 12-14v

Engine off, no current drain, battery in good condition, min 12.5 volts.
Engine running with near fully charged battery, 13.9-14.5 volts max

A battery showing less than 12 volts, with no drain is ...Kaput... or totally discharged.

Also to test alternator, when engine running, monitor voltage, and apply a load... head lights, rear screen heater, rear guard lights, brake lights etc, voltage should be close to 13 volts, if not, just add a few revs, if the fan belt squeels, it might need a bit more tension.:thumb2

 

[briggie]

cold weather kills batteries too

 

[Ogri]

Just like to say that it's worth taking all these readings both on the battery posts and also on the battery clamps to rule out a bad post /clamp connection. Was once embarrassed to have this pointed out to me by an RAC man...

 

[AlexD333]

good battery off load should read 12.8 volts engine running should be 14.2 ish, but this is no guide to the batteries capacity, the best way of determining this is with a high amp discharge meter, not many garages bother with these any more, preferring computer crap instead but they do not place a good load on the battery so the results dubious, Rick

Yup, my battery reads 12.8 volts on multimeter with engine off :thumb2

 

[macabethiel]

Battery failing ?

I knew my old battery was giving out when I checked the voltage when the vehicle had been stood for a couple of hours and the post voltage was down to 11.8 volts dropping to 11.6 volts overnight during the cold snap.

It was charging OK reading between 13.2 and 14 volts on my cigarette lighter digital voltmeter. If I turned the switch to accessories with everything off it would read 12.3 volts but a couple of hours later it was down to 11.8 volts. ( I had previously charged the battery fully the previous weekend.)

Trouble is if you keep running as long as you can with a failing battery you can end up with alternator rectifier failing if its giving high charge for a long period especially on an older vehicle. That been my experience in the past.

 

[johnb5177]

cold weather kills batteries too

As it did to mine yesterday morning, just as I was setting off for an appointment with a client........not so easy out here getting stuff, so had a run around but with a good result.

 

[terrano bob]

Engine off, no current drain, battery in good condition, min 12.5 volts.
Engine running with near fully charged battery, 13.9-14.5 volts max

A battery showing less than 12 volts, with no drain is ...Kaput... or totally discharged.

Also to test alternator, when engine running, monitor voltage, and apply a load... head lights, rear screen heater, rear guard lights, brake lights etc, voltage should be close to 13 volts, if not, just add a few revs, if the fan belt squeels, it might need a bit more tension.:thumb2

:clap :thumbs

 

[supergnome]

When you've done the tests find the bill and it should have a guarantee period on it. Got to be at least 2 years. Get it replaced.David.

 

[John B]

Thanks for all the help :thumb2 My findings are
Engine off is 12.6 v
Engine running is 14.2
Engine running with lights blowers and heated screen is 12.8 v but started to drop as car was only on tick over ?? But would I be correct if I said that the battery may not be holding charge ?? Cheers

 

[briggie]

id check alternator output first

 

[John B]

id check alternator output first

Isn't that the same as having having the engine running ??

 

[rustic]

Isn't that the same as having having the engine running ??

On tick over, some alternators haven't started to give any great output.
With your voltages, dip the throttle slightly, say to 1500 rpm and the lights should go bright, and the voltage up to 13.5 + volts almost immediately, if the Alternator is working ok.

 

[briggie]

On tick over, some alternators haven't started to give any great output.
With your voltages, dip the throttle slightly, say to 1500 rpm and the lights should go bright, and the voltage up to 13.5 + volts almost immediately, if the Alternator is working ok.

also check alt belt for tightness / condition :thumb2