Flat battery, won't start. Some advice please.

[ScottR400D]

I agree if we're reading that right. You measured the voltage while the engine was running at 3000rpm?

 

[Golf Juliet Tango]

Hi Alan

I'm sorry to hear of the disspriting start to your ownership. 

I am assuming the alternator is charging the battery.

I had this issue with my 21 when I first bought it. Just fit a battery isolator key and use it. Anything else is just messing about.

[AlanO]

Hi Scott. Yes, voltmeter didn't flicker when revs increased up to 3,000rpm. Stayed on 12v all the time. I assume an alternator issue (or regulator?) but in any case I'll speak with CC tomorrow. I'll also remove battery, charge it and see if it holds charge.

[AlanO]

Hi Scott. Yes, voltmeter didn't flicker when revs increased up to 3,000rpm. Stayed on 12v all the time. I assume an alternator issue (or regulator?) but in any case I'll speak with CC tomorrow. I'll also remove battery, charge it and see if it holds charge.

[AlanO]

Hi Stephen. I've learnt the phrase, TADTS!! But a bit peeved it's looking like the alternator and so something so basic. Never mind, we'll get there!

[Piers300]

I would also examine and check the wires and connector to the alternator. Give them a close inspection for a bad connection. I do however suspect you have a faulty alternator.

Piers

[john milner]

My recommendation is for everyone to get a cheap plug in the fag lighter voltmeter even if just to get a feel for what normal looks like.

[Jonathan Kay]

"My recommendation is for everyone to get a cheap plug in the fag lighter voltmeter even if just to get a feel for what normal looks like."

Electrical problems are clearly common on Sevens. I agree that it's smart to monitor a few simple things in the same way that we do for tyre pressure and level of coolant and engine oil... and battery acid where appropriate.

I suggest that the basic set is the battery voltage at rest, minimum during cranking, and at 3,000 rpm.

It's then a lot easier to spot deterioration by comparison with previous values.

I'd recommend a multimeter because it will do other things, but you can measure those voltages with a small digital voltmeter as John says, and there are also some units that provide a cigar lighter socket, one or more USB charging sockets, and a similar voltmeter. I was concerned that those little voltmeters might be overdamped and that they couldn't be used to show the transient minimum during cranking, but with a sample of 2 (!) that hasn't been the case. (This is a separate issue from the much shorter transient drop that Andrew Revill identified as the problem with a certain type of starter. That required an oscilloscope.)

Jonathan

PS: As always I'm happy to supply wiring diagrams for Sevens and to recommend a multimeter.

 

[AlanO]

Feel a bit of a numpty for not having spotted earlier that one of the alternator connections has burnt out, presumably been loose for some time, overheated and corroded. Cleaned it up back to bright metal for a temporary repair and battery now reading 13+volts with engine running.

Looking on the bright side, learned a bit more about the car, and learned from everyone who offered suggestions & help.

[ACFowles]

I've got a "bM2 battery monitor" (search Amazon or eBay) on a couple of cars.  Combined with the phone app it allows me to monitor the battery voltage, charging status etc. Works well for me 

[AlanO]

On my to do list (lessons learnt);

A) fit battery immobiliser

B) fit voltmeter/battery monitor

C) include electrical connections with regular 'spanner checks'

D) check battery levels with other liquid checks.