Do you want the Road Tax system to change? Do you have thoughts on the potential changes to the Road Tax system? | No thanks
MK4 VW Golf GTI - persistent flat battery - a alldritt

We are having a persistent electrical problem.Because it constantly would not hold a charge for any length of time we had assumed it was in need of a new battery.Went off to Halfords for a replacement who after testing it said there was nothing wrong with it and suspected that it was draining by something unseen ie boot lights,door lights,etc etc.I had previosly checked and eliminated those.Then it would not re-start so Halfords staff tried jumping it with an industrial boost charger to no avail - they then bump started me to get home and we took it to our local garage who look after our cars.And they have tried everything over a period of weeks to get to the bottom of the problem - including a visit from a specialist auto electrician.Radio (they are known to be a problem), alarm,door locks have been in turn all eleminated.My charger whilst 4 yrs old has hardly been used and is now failing to charge it ,so, at the weekend i borrowed an old but serviceable unit and after 4hours the car started OK.I put it back on charge Sunday (thinking that the start would have taken the best of it) and now Monday lunchtime it will not start!!!!Help or ideas would be useful - i am beginning to think that although quite new it really is the battery.During charging/attempting to charge i have disconnected the battery from the car electrical circuits.

Edited by a alldritt on 24/10/2016 at 14:43

MK4 VW Golf GTI - persistent flat battery - RobJP

Isolate to determine the problem.

Take the battery out of the car. Charge it up. Take readings of the charged state. Leave it overnight. Take fresh readings. Compare.

Then you'll really know if it is the battery failing. Anything else is guessing.

MK4 VW Golf GTI - persistent flat battery - Peter.N.

Check that you have around 14.4 volts across the battery with the engine running, if OK check the alternator for leakage with the engine off by disconnecting the battery feed and connecting an a multimeter in series with it set to the 'Amps' range.

MK4 VW Golf GTI - persistent flat battery - Railroad.

There are three reasons why a battery goes flat.

1. Battery unservicable.

2. Charging system fault.

3. Electrical drain.

Check the charge rate by using a voltmeter. With all electrical loads on and with the engine running the charging voltage should be around 13.5 volts, and around 14.4 volts with all loads off.

Use an ammeter connected in line with the battery earth terminal and post and see if there is any current being drawn when the keys are out of the ignition and the car is locked. There should not be any more than 0.1amp. If current is being drawn then this will be the reason why your battery is discharging. You'll need to isolate circuits to find the cause.

Batteries fail for a number of different reasons. To simply say a battery is 'faulty' is no description at all. There will be a specific reason why it's faulty, and this is why the result from a battery tester cannot always be relied upon. You should be aware that car batteries are not deep cycle batteries, and often don't properly recover if allowed to completely discharge, especially in extreme hot or cold conditions.

If tests 1 & 2 prove good then you should replace the battery, regardless of what Halfords have told you.

Edited by Railroad. on 25/10/2016 at 09:37

MK4 VW Golf GTI - persistent flat battery - Wackyracer

If you have a multimeter with a min max hold facility, connect it across the battery and then crank the engine. The Min voltage should not go below approx 8 volts. If it doesn't go below 11 volts I'd suspect another possible cause, high resistance in battery cables to the starter motor or indeed the starter motor itself is faulty.

Edited by Wackyracer on 25/10/2016 at 10:58

MK4 VW Golf GTI - persistent flat battery - Railroad.

Check battery to starter and alternator cables, as well as earth cables by carrying out a voltage drop test. Volt drop must not exceed 0.5v. If it does you have a bad connection or a high resistance in a cable.

MK4 VW Golf GTI - persistent flat battery - a alldritt

On Tuesday I charged the battery with a known "good" charger prior to which it was reading 10.57v.When I rechecked it some time later the reading had risen to 13.8v but by the following morning it had lost 4v - all checks were made with it disconnected from the car circuits.
At that point I purchased a new battery and that's where I am now.I believe Halfords were "mistaken" and that that information (its serviceability) was then passed to the garage who then started checking for possible current drain from other sources (unless there ARE more than one snag).The Alternator output has been checked and is OK.
I shall try checking it each morning, however one of our problems is that its a second car and is rarely used - we have a larger more useful, newer estate.
Many thanks for contributors help and suggestions and I will report back further.

Best regards,

Alan

MK4 VW Golf GTI - persistent flat battery - Falkirk Bairn

>>however one of our problems is that its a second car and is rarely used

When SWMBO's mileage fell I made a point of running it 2 days x per week.

For a couple of years it was OK but then problems with battery, brake calipers (lack of use) & other niggly things to do with low usage.

Decided to sell & live with just one car - being retired it's OK .

MK4 VW Golf GTI - persistent flat battery - Cyd

however one of our problems is that its a second car and is rarely used

think ... nail .... head

buy a conditioner to keep it constantly topped up. Draper do a simple plug in job that I use.

https://youtu.be/AT_XmlwMVz4

MK4 VW Golf GTI - persistent flat battery - focussed

Lidl do some really neat little automatic chargers that can be left connected to a battery permanently to maintain it's charge.

www.kompernass.com/admin/view/manual/IB_74798_ULG3...f

 

Ask Honest John Right column

Value my car