Diagnosing potential battery/alternator problems

[TAR]

I'd also be suspicious of the CTEK charger, it shouldn't let the battery overcharge by that much. 

As for testing the alternator, do that with the new battery but if you measure a really high voltage, turn it off quickly. The new battery should easily cope with a small time being over charged. 

I suspect your alternator will be OK and your CTEK will have ruined the original battery  

[paulbrown22]

4 hours ago, GreenGoddess said:

Thanks Paul. Do you know if the alternator on these cars has a separate regulator than can be changed? Or do I need to buy the complete alternator unit?

Thankfully I haven't yet had to take my Esprit alternator apart, but I don't believe the factory OEM alternator has an external regulator - think it's all within the housing. If you do end up removing it, potentially worth taking to a trusted local alternator specialist for refurb/testing rather than buying a new probably far-eastern copy, as you hear lots of dubious stories about them!

[Rambo]

Totally agree with that sentiment. If it proves to be faulty, send it to an expert  who can recondition your existing one whether it be windings, regulator, diode pack etc.... and then properly bench test it.

 

[GreenGoddess]

5 hours ago, Rambo said:

What is its Ah (amp hour) rating? Usually the lower the rating the cheaper it is.

I was going to recommend a Varta silver.

It’s 54Ah. The manual recommends 55Ah so it’s close enough. 

[Rambo]

I always go for the highest CCA (Cold Cranking Amps) and highest RC (Reserve Capacity) I can find, providing it fits into the battery compartment. It's particularly beneficial in a cold climate.

[snowrx]

18 volts on a resting battery is very high. Can you access another voltmeter for a second opinion?

[GreenGoddess]

57 minutes ago, snowrx said:

18 volts on a resting battery is very high. Can you access another voltmeter for a second opinion?

You might have something there! I don't have another voltmeter but I have just tested an 18v drill battery and it measured 22v. I also tested a 9v drill battery and it measured 12v. A 1.5v AA battery is measuring 2v. Arrrgggh! 🤬

So it looks as though my Chinese voltmeter may be a pile of junk. I suppose I better hurry up and cancel the order for the new battery and order a new voltmeter instead!

[Rambo]

You still have a battery and/or an alternator problem 🙁

Remove battery and take it to a motor factor for a (free) load test. They should tell you whether it is goosed or not.

I still suspect a parasitic drain from the alternator (regulator/diode pack malfunction) which has fried your battery.

But, hey, what do I know?

[GreenGoddess]

Thanks. I'll probably do that. I am leaning towards it being a faulty alternator because the voltmeter on the dash is showing a low reading (11v or so) when driving. I have cancelled the order for the new battery and have ordered a new multimeter. I can always order the battery again if it proves to be fried.

[GreenGoddess]

Sorry for the delay in updating you guys. 

It turns out that my cheap Chinese multimeter was giving false readings so I bought a new one.

After being fully charged and left sitting on a bench for a few days, the battery measures 13.2v. I also bought a battery load tester and the battery tested fine. Even after load testing, the battery is still giving out 13.2v.

Today I fitted the battery back into the car and measured the voltage coming into the battery from the alternator. It is 14.28v with the engine at 1500rpm. The voltmeter on the dashboard is showing under 12v so I suppose the gauge must be out of whack.

After taking the car for a decent drive, the battery now measures 13.8v with the engine off and 14.28v with it running at 1500rpm.

The resting voltage of 13.2-13.8v seems high but do you think it could be causing the radio cassette glitches? The indicators (turn signals) are working but don't seem to be flashing normally i.e. they seem a bit slow but perhaps that's just my imagination.  

[fjmuurling]

Now you have healthy voltages at the back of the car it is time to check voltage on the front and compare them to the voltage on the back. (Also test under load ie lights on).

There can be bad connections between the front and the back of the car. (earth straps is one possibility).

Compare the readings with what the dash gauge shows. (maybe your dash gauge is OK).

 

[GreenGoddess]

Thank you Freek. I didn't think of that! I have a lot l to learn 😒. I will start checking some voltages in the cabin to see what I get. I will report back!

[LotuStuart]

20 hours ago, GreenGoddess said:

Even after load testing, the battery is still giving out 13.2v.

Is it a wet lead acid battery or a gel type lead acid, or a Lithium, or other?

Generally wet lead acid produce 2.1v per cell, with 6 cells which is 12.6v. More than that is weird.

[GreenGoddess]

On 16/01/2023 at 11:18, LotuStuart said:

Is it a wet lead acid battery or a gel type lead acid, or a Lithium, or other?

Generally wet lead acid produce 2.1v per cell, with 6 cells which is 12.6v. More than that is weird.

I think it’s just a standard wet lead acid battery. 

Are there any common places where I might find a bad earth that would affect the cabin electrics? I really don’t know where to start looking. 

[drdoom]

Check the dash scuttle beam,  also the bolts attaching top of rad to boot floor bobbin, aft check whatever points the battery and block have been earthed to the chassis.

Cheers