Starting

[Swifty75]

Hi All

My Mk1 decided not to start the other day after I had taken my lad to football training, luckily one of the other dads had some jump leads in his car (mine were in my garage=useful). I ran it the 10 miles or so home, and put it on charge. When it was full I coupled the battery up and took it for a 20 mile run, this was on Sunday. I went to start it today and it would not start again. I have put it on charge and it charges quickly to nearly 13 volts (literally 5 minutes), when I take it off charge it goes down to 12 volts (nothing attached), very quickly. It looks quite new, although I don't know how old as it came with the car a year ago.

I am presuming my battery is fried?

Thanks for any help.

Neil

[Lingen]

Neil.
Either it is fried, or something is draining it. I suggest you charge it again, and then disconnect one of the battery leads. Leave it for a day if you can, re-connect and see what happens.The fact that a gauge is showing 13 volts really tells you little or nothing about the condition of the battery. No start=new battery time.
mike.

[marshman]

Probably but not necessarily!

When you connect your charger to a totally "flat" battery, or nearly flat battery, it will take at least X/Y hours to charge, where X is the Amp/hour capacity of the battery (for a Stag battery it is usually around 60 Amp/Hours (abbreviated to A/H)) and Y is the charging current from the battery charger - if it is a fairly modern charger then assume around 4 Amps. So in a typical case it will take 60/4 = 15 hours (AT LEAST) to fully recharge the battery. In actual fact it will usually take longer as the current reduces the nearer to fully charged a battery gets.

You don't say how long it took your charger to get to "full", I would suggest if it was less than 12 hours then either the charger is not doing its job properly (not unusual for a lot of modern electronic chargers) or the battery is past its sell by date. You also don't say if the alternator is charging the battery properly, What voltage does the volt gauge on the dash show when driving? They are not always very accurate, but they can be a good indicator. In cold weather, a cold start - especially if the car doesn't fire up first go - can drain the battery significantly. Then driving off with the blower going, lights on etc. means that even a 20 mile drive is insufficient to replace what has been taken out - especially if the alternator is not charging correctly.

As an indication when a battery is nearing full charge the voltage (with the charger connected) should be over 14.4V. Nearly 13V is no where near fully charged!!

I would double check the alternator is charging properly and you are allowing enough time for the battery to charge - lots of short runs (10 miles is short in my book) - in winter especially will soon kill a battery if the charging system is not up to scratch. If it is OK and the battery still dies after a good 24 hours on your battery charger then replace the battery. Just replacing the battery without checking everything else could land you in the same position in a few months time.

Hope that helps

Roger

[Swifty75]

Thanks for the replies so far.

In answer to a couple of questions:
- the battery reads 14.4 volts when attached to the charger (multimeter on battery) & 13.1 volts with charger just removed.
- when running at a steady 50mph, the voltage gauge is reading over 15v.

i have just been into the garage and disconnected the charger and with nothing attached in 5 minutes it had dropped from 13.1 to 12.6.

cheers Neil

[Lingen]

That is fairly normal Neil. Try it again tomorrow morning.
Mike.

[StagJonno]

With a lead acid battery with no load and no charge after resting for ~1/2 hour, 12.6/ 12.7V (measured with a multimeter) indicates roughly 100% charged. 12.0V is ~flat. This characteristic is near enough a straight line, so you can calculate the state of charge for intermediate voltages. (These figures are for ~20C, a bit lower at temps 0 - 10C).

As Roger says, the Voltage shown on the dash meter isn't necessarily accurate. However, I would be concerned if it shows a voltage greater than 15V and I'd be looking to see what a multimeter shows at that time. If it is truly 15V or greater and is sustained, then it will reduce the battery life - I'd suspect the alternator regulator is not working correctly.

Jonno

[Swifty75]

Went to it again this morning, it was showing 12.5V (Multimeter), I had left the battery uncoupled last night. I coupled it up and it started first time. I connected the multimeter to the battery and whilst running it was 14.4V on the multimeter and 15V on the gauge. At idle (800 rpm) the multimeter dropped to 13.2V.

After running for 10 minutes it was showing 12.6V when I turned it off. I have left it coupled up and will check the reading without moving over the next few days. There could be something drawing charge off the battery.

Thanks for all the help.

Neil

[jakesmig]

Sounds to me like a bad earth kidding on it's a dodgy battery.

[StagJonno]

Common unwanted drain causes are boot light and glove box lights not switching off. Also if there's anything plugged into the cigar lighter socket (this remains live with ignition off). Breakdown of the diode pack in the alternator another possible cause.

Easiest way of tracking down unwanted drains is to get hold of a clamp ammeter capable of measuring dc current such as https://cpc.farnell.com/tenma/72-298...-dc/dp/IN07620 priced at £36. I think cheaper versions are available (check Amazon), but make sure it does dc amps and has a low enough range to pick up on the size of currents likely to be involved (250mA - 5A). The clamp function saves having to disconnect any wires as you just clamp over individual wires and look at the reading (always worth checking twice, the second time with the clamp turned through 180 degrees and take the average to eliminate influences of adjacent circuits/ equipment). Start with the main battery connection, then if this confirms drain, alternator power lead (the fat one) then the circuits connected to the fuse box (behind the parcel tray).

Jonno

[Swifty75]

Checked today and the battery charge is now 12.3v with the car Attached. Seems like something is drawing from the battery. Will checkbagain tomorrow. I will then put the multimeter into the system and check what is drawing by pulling the fuses. Could still be the battery though not holding charge.

thanks all
neil

[Tdm]

Checked today and the battery charge is now 12.3v with the car Attached. Seems like something is drawing from the battery. Will checkbagain tomorrow. I will then put the multimeter into the system and check what is drawing by pulling the fuses. Could still be the battery though not holding charge.
thanks all
neil

If you put a Battery "Cut Off" key in the Earth cable, remove the key and the Battery still drops voltage - then it has to be the Battery.
Whenever I fly to the U.K., I park the Stag and remove the Key so nothing can drain it while I am away, and when I come back (could be a couple of weeks or a month later),
I re-insert the Key and she starts straight away.

Of course if it's not the battery then you have to find out what is draining it, and has already been mentioned, possible causes are - Glove box light, boot light, radio, or something left plugged into the cigar lighter socket, or a bad earth etc.

[Swifty75]

Pretty certain it is the battery. Went to it today and it was at 12.25v. Tried it and it was dead, that took it to 11.9v. Put it on charge for 15 minutes and it then showed 12.9v, it then started first time. It charges quickly but loses charge quickly which is the sign of a poor battery.

Think I will replace and see how it goes.

thanks to all for words of wisdom

Neil

[marshman]

I think you maybe correct, classic symptoms of a battery that has lost its capacity, i.e. the amount of energy it can store. I have several old batteries "lying around" that exhibit the same symptoms. They are supposed to be 40AH capacity but when I checked them recently - timed discharge through a known load - they had a real capacity of less then 10AH. Enough to start a car if fully charged, but if it doesn't start first time or is left with the lights on for any length of time the battery goes flat. They also have a tendency to self discharge quite fast.

On a related note in the winter (or when it is really cold) it is possible for the electrolyte in the battery to freeze. A fully charged, healthy battery will be OK down to around -45 deg C. But if the battery is in poor health and/or is discharged (i.e. flat) then it is possible for the electrolyte to freeze at less than -5 deg C. If the electrolyte does freeze it is likely that the plates will get distorted and the battery ruined, if it wasn't already! Yet another reason to keep the charge in your battery "topped up" in the winter if you don't regularly use your car.

Roger

[Swifty75]

New battery is now in place, car seemed more eager to start. Did 40 miles in it no issues, I will see next time I go to it in a few days. Bloke at the battery shop tested it and said it was knackered though.

only thing is that the fool that changed it (me) put the washer bottle next to the manifold to get the power steering pump away to get access to the battery. I then installed the battery, put the power steering pump back and forgot about the washer bottle. It is now melted but still holding water. The water did get nice and warm though!

thanks for all the help!

Neil

[mopoole]

New battery is now in place, car seemed more eager to start. Did 40 miles in it no issues, I will see next time I go to it in a few days. Bloke at the battery shop tested it and said it was knackered though.

only thing is that the fool that changed it (me) put the washer bottle next to the manifold to get the power steering pump away to get access to the battery. I then installed the battery, put the power steering pump back and forgot about the washer bottle. It is now melted but still holding water. The water did get nice and warm though!

thanks for all the help!

Neil

You're lucky, mine didn't hold the water