This is driving me round the fecking bend now for MONTHS. Seems my Polo has a longing to be a Hybrid - you have to charge it to go anywhere. It used to be, the battery went flat after a few days if you didn't drive it, and if you tried to start it after just leaving it overnight, it'd only start about 1 time in 3 - the other 2 times it just kicked the starter over weakly, the trip counter would reset and the stereo would go mental (stock tape deck). Charge it for an hour and it used to kick over fine, and be okay for the day you drove it.

Then it just got worse, would start if you jumped it, and run fine, but if you stalled, or parked, it'd never start again without help, sometimes even having to kick it over with the charger still attached.

So i thought 'okay, the battery has warped plates or the electrolyte is low' - battery is one of those stupid new ones where you can't check the levels, it's all totally sealed. Bin it? *sigh*

So...got a much bigger Bosch on there - a 70Ah one (bear in mind i only have the 1.4 8v engine) that doesn't quite fit in the tray - it's just a stopgap though. Charged the battery, kicked over nice and strong. Stopped the engine, tried starting again? Yep, started. Stopped it again and restarted, noticeably weaker, but still kicked it over okay. Was happy with that.

Then i go and get rushed into hospital for torn tendons, and can't drive. Car's parked for 2 weeks. Try to start it? *whine, groan, nothing*...

Okay, charge it. Overnight charge = wouldn't start. WTF? Left it for another 30 minutes and it started. I thought to isolate the radio by pulling the fuse, in case it was the current draw for that keeping the thing from working. Nope - wasn't that. There's no drain i can think of (there's no Alarm), although i'll test later with a multimeter if it stops raining.

Either some magical voodoo ritual has been performed on the car, the replacement battery i have is also crap & has warped plates/low electrolyte or something is seriously wrong! Bad alternator circuit/Starter Grounds?

Just to add; i came back from the shops about 2 minutes ago. After being charged for 20 mins or so, it started up and i drove to the supermarket with no issues, but starting it up again once i was finished was a bit touch and go. On the way back, again, no problems driving at all. However, my foot slipped on the clutch when i got in, and it stalled. Tried to restart, and it's as if the battery is totally dead - tape deck whirrs away like a spastic, and the starter just doesn't want to know...duff battery #2, or alternator not charging? I'll bung it on charge again for an hour, try and start it & measure the voltage.

I'm hoping it's not going to need another battery - new ones are £80 out here :'(

itl probably be your battery dude.

if your alternator werent charging and your battery died also, it probably wouldnt run (thats what happend to the guy who bought my old mk2)

I thought it was just me killing batteries too - but mine's on it's THIRD. And that's a Bosch one too. Tried the biggest one I could fit in there, and it's still tempermental..

Checked with the multimeter and the resistance of the earth to engine is 9.1 ohms. Seems a bit high tbh. Never got round to testing the live feed. Battery sits at 13.4v when "charging". Need to check the alt too.. :/

shouldnt it charge at 14.7 volts?

14.4 was my recollection..

9.1 is way too high.

Your looking for at least 0.2 or less really.

Best way to isolate it is to set the tester up and then remove and replace fuses to at least track down the circuit responsible.

Some cars have certain bits that stay active for a time after the ignition is switched off.

9.1 is way too high.

Your looking for at least 0.2 or less really.

Best way to isolate it is to set the tester up and then remove and replace fuses to at least track down the circuit responsible.

Some cars have certain bits that stay active for a time after the ignition is switched off.

Yeah, i know. But the connections are clean, it seems to be the actual cable. I did adv physics at school, doing Mech Eng at uni so I atleast know that 9.1 is too high! :p

Gonna look at the big 3. Or, atleast a bigger 3 than what's in. Standard should be fine though, accounts for the low battery voltage too.

Do you test the strength of the battery? When it doesn't wanna start and seems like the battery is flat, do you test the battery (unconnected to the car) to check it's strength?

Sounds very much like a bad high ampage connection to me. Battery terminals, starter terminals, alternator terminals or engine earth terminals.

Even with a strong battery, a poor connection will have things like the windscreen wipers trying, but moving slowly. Poor connections are also inconsistent/temperamental.

How old is the battery? Is it a maintenance free one?

it sound exactly the same issue as mine when the battery started to die.

Constant boosting/charging from dead will mess the battery up further. Even a new one will have a shortened life span.

It may pay to double check that cable resistance by measuring the volt drop over the cable and its terminals, but first of all, test your battery under load:

Draw the engine fuse in order to prevent it from starting (fuse 15?)

Connect your voltmeter across the battery terminals (11.5 to 13.0V)

Get an assistant to operate the starter, VM shouldn't fall below 9.5V

Connect VM between battery +ve terminal and the starter main terminal - operate the starter - VM shouldn't read more than 0.5 V

Connect VM between battery -ve terminal and the engine - operate the starter - VM shouldn't read more than 0.5V

Anything LESS than 9.5V in the above test indicates a weak (or flat) battery.

" MORE " 0.5V " " " " " high resistance in that circuit.

Replace the fuse.

Make sure that EVERYTHING is switched 'OFF', including closing the doors etc.

Disconnect the negative battery terminal and connect your AMMETER set first of all at, say 20A between the battery terminal and the disconnected lead terminal, if there appears to be little or no reading, disconnect the ammeter and drop it down to 10 Amp range - Continue with this until you find what, if any, current is being drawn.

What rate are you charging the battery at? Unless you have a high(ish) battery charger output, the odd 1hour charge will make very little difference, especially to your 75 AH battery.

Sorry if this is a bit long winded, but if you follow it, you should be able to locate your problem.

Regards,.

i was about to add the above- its definetely a short somewhere, and it sound like its on a permanent live circuit not a switched live- I've fixed these many times and the most common culprits are stereos (have you fitted an aftermarket unit?) and strangely enough the instrument panels! has an aftermarket alarm been fitted? have you messed with headlights or foglights?

it only takes a small short to create a power drop and it will stop the charging of the battery.

Okay - been out and checked things (nice day + i got my multimeter back).

Battery Standing voltage = 13.03v, just about kicked the starter over.

Voltage at battery terminals when idling = 14.5v to start, dropping by approx 0.1v per minute - would stabilise if you give it a little throttle, but not increase the voltage. When you come off throttle, you get a 0.1v spike momentarily at the terminals, before the voltage starts falling off again.

Vampiric drain on the battery = 0.02amps (radio memory). With door open and interior light on, it's 0.9amp.

So it looks like the alternator and possibly the battery is a bit cack as well. I'll clean up the positive lead on it, looks white and powdery, but at this point, i'm grasping at straws.

*sigh*

Looks like another €120 out of my budget -_-