matttromans 0 Posted September 10, 2012 Ok, so i've got a bit of an odd starting problem which i'm hoping the collective Corrado Forum mind might be able to shed some light on! My VR6 seems to have stopped holding electricity. The battery is a pretty new Halfords battery. I've been to Halfords and had them check it. Its apparently fine. The symptoms are as follows: If I use the car day to day it is fine. Starts first time every time. If I leave it for a week the battery will go completely flat (not even clicking when you turn the key). Plug the charger on for 10-15 mins and the car will fire straight up (not just turn over a bit and reluctantly start - I mean fires straight up). You can then drive it for any distance using as many toys (stereo, seat heaters, the lot) as much as you like. Turn it off and it will start straight up again. What I don't understand is how a 10 minute charge can be enough to get the car to jump into life so readily? I've checked that there is nothing silly remaining on after turning it off (boot light, stereo etc). I've checked the battery terminals (tightness and corrosion). Next I was going to disconnect the battery for a week after a good blast just to check if the battery is holding charge - worth it given that Halfords have run their diagnostics on it? Following that I was going to get a multimeter out and see if there is any drop across the system? Any other ideas? Thanks. Quote Share this post Link to post Share on other sites
Kevin Bacon 5 Posted September 10, 2012 The battery *is* knackered. Putting a voltmeter across it is by no means an exhaustive test. Had exactly the same symptom in my BMW 525i before I sold it. If left for a few days, nothing. 10-20 min charge, then it fired immediately. New battery and the problem went away completely. Varta Silver Dynamic from battery2u.co.uk. 74AH. But you can also check for an excessive current draw by putting an amp meter between the battery post and the positive lead. Anything over an amp will drain it over a few days. I think the default draw is 0.1 amp. Quote Share this post Link to post Share on other sites
matttromans 0 Posted September 10, 2012 Kevin thanks - that was my suspicion despite what Halfords have said. I'll check for an excessive draw just in case, but I think the battery is toast. Halfords are normally pretty good at exchanging knackered batteries, unfortunately once the car is going and charging it I think it 'reads' as being fine, so they won't exchange. Quote Share this post Link to post Share on other sites
craigowl 0 Posted September 10, 2012 I ended up using a trickle charger. Never a problem for 11 years - same battery! A lot of people have trouble with VR6 battery going flat after a fortnight if car unused. Endless speculation to cause - from boot light remaining on to idiosyncratic behaviour, possibly due to factory immobiliser. Many a good battery has been scrapped because of this, I suspect. Quote Share this post Link to post Share on other sites
VR6 0 Posted September 10, 2012 The battery is a pretty new Halfords battery. Has it ever sat / been allowed to go completely flat? Long periods sitting dormant (mixed with cold weather) can mean instant death for even a fairly new battery. Quote Share this post Link to post Share on other sites
matttromans 0 Posted September 11, 2012 Kevin thanks - that was my suspicion despite what Halfords have said. I'll check for an excessive draw just in case, but I think the battery is toast. Halfords are normally pretty good at exchanging knackered batteries, unfortunately once the car is going and charging it I think it 'reads' as being fine, so they won't exchange. OK, So last night I attacked the car with a multimeter and a friend who is more knowledgeable on car electrics than I am. Firstly we tried removing the positive battery connection and wiring the amp meter in series. We couldn't get a reading. We then took an interior bulb and wired that in series as a check. With the alarm on the bulb flashed in sync with the dash alarm led. With the alarm off the bulb didn't light. We then checked the voltage of the battery which was reading at 12.3V. We then fired the car up and took another reading across the battery at 14.3V, so it appears to be charging. Any thoughts? Sound like a dud battery to me.... ---------- Post added at 9:16 AM ---------- Previous post was at 9:15 AM ---------- Has it ever sat / been allowed to go completely flat? Long periods sitting dormant (mixed with cold weather) can mean instant death for even a fairly new battery. The battery has gone completely flat several times. Most recently when it has done it only requires a 10-15 min charge and the car will fire straight up again. Quote Share this post Link to post Share on other sites
tonytiger 0 Posted September 11, 2012 The battery has gone completely flat several times. As VR6 said, that's not good. Are you using a cheap/basic/rapid charger to charge it up again? Have you tried charging the battery for a couple of days to see if that helps. I know you can get fancy chargers these days that I've heard can condition/revive batteries - but whether the expense of one of those would be of benefit it's hard to say. You might be as well just getting a new battery. How did Halfords test the battery, and did you watch them test it? Perhaps you could go somewhere else that does free battery checks and see what they say? However, you really do need to find out if there's simply something draining the battery too quickly first. Quote Share this post Link to post Share on other sites
Kevin Bacon 5 Posted September 11, 2012 Strange that you didn't get a reading with the ammeter. I use an automotive digital meter set to amps and I always get a reading. You need a meter that can handle at least 10 amps because the initial current draw when you reconnect the live circuit is enough to blow the fuse on some cheaper, low current meters. For what it's worth, I got exactly the same readings when I tested my BMW battery. It showed over 12 with the car off and ~ 14 when charging. That would appear to be 'normal', but chances are one or more of the cells are dead / dying. Certainly the latter reading is a sign the alternator is working, but 14.3V is very high. It means the alternator is working hard to recharge it. Normally you should see around 13.8-14 across a healthy battery. I would get the battery I recommended personally. Varta are a very good brand and rarely cause problems. Quote Share this post Link to post Share on other sites
VR6 0 Posted September 11, 2012 It's worth testing with the car running and then also doing it with everything turned on as well ... stereo, rear screen, lights, wipers, heaters, air con (if you have it obviously) etc. Quote Share this post Link to post Share on other sites
Kevin Bacon 5 Posted September 11, 2012 Bridge fan speed 3 with the engine running! That will show up a weak battery :D Quote Share this post Link to post Share on other sites
