36 replies to this topic

[Doovydoo]

Hi guys and girls of TMF, 

 

it seems, only 6 months after buying a new battery - see previous topic here: http://www.theminifo...rging-question/  -  this one too has gone flat and cannot start the car.

 

Either it's because I haven't used it much over the past months (been on holiday for 3 weeks) or I have another problem that is leading to the batteries not being charged properly (alternator trouble?)

 

On both occasions the car hasn't been used much though..... so it could be that?!

If anyone has any ideas for me I'd be glad to hear them please..!

 

It's on charge again now, and I will be using the car a lot more in coming weeks so can keep an eye on it in regular use. 

 

 

p.s. I have no alarm, only a Head Unit and Sub woofer are the additional load, and with working Remote wire connections.

 

thanks in advance!!

Edited by Doovydoo, 01 July 2013 - 09:21 PM.

[KernowCooper]

Only way your going to find out is to put a multimeter on the battery and check the charge rate , have a read of the guide I did here http://www.theminifo...ng-basic-tests/

[corrado vr6]

Best bet would be to get the car started and check the voltage (using a multi meter) that the battery has when the car is running, once you know report back here and you will soon be told if your battery is being charged

[Bungle]

as above check the car is charging and also switch you multi meter to amps and check for a current drain

 

ammeters must be fitter in series , so remove a lead and fit the meter between the lead and the battery

[Doovydoo]

Only way your going to find out is to put a multimeter on the battery and check the charge rate , have a read of the guide I did here http://www.theminifo...ng-basic-tests/

 

Wow, that's pretty much exactly what I needed.. cheers for that!! Fantastic guide! Now to get hold of a multimeter..

 

 

Best bet would be to get the car started and check the voltage (using a multi meter) that the battery has when the car is running, once you know report back here and you will soon be told if your battery is being charged

 

I will do :) 

 

 

as above check the car is charging and also switch you multi meter to amps and check for a current drain

 

ammeters must be fitter in series , so remove a lead and fit the meter between the lead and the battery

 

I hate wiring and electrics, it's my one hate of working on cars... will do my best to see though, thanks :)

[Doovydoo]

Hi guys (again).

 

So just two weeks after recharging the battery and using the car a few times, it has gone completely flat again.

 

So now I have a multimeter and will check the amps etc once it's charged back up again, to see if charge getting to the battery / current drain when car off.

 

Also a question - I have seen it recommended to check the earth strap (something I had not heard of previously!) - is this it, in my engine bay?

 

The braided cable from gearbox

 

 

and you can just just about see it running underneath there

 

 

 

if so, it looks a bugger to get to..!! The one in rear boot is fine, connected solidly. Arrrgghh this is annoying   any help appreciated!! thank you!

[KernowCooper]

Yes thats the engine earth cable, get the car running and put the multimeter on volts and red on + and black on - on the battery run engine at 2000rpm battery volts  should raise to 13.7-14.2v after 4 hrs + standing the batery voltage should be 12.65v = 100% charged.

[Captain Mainwaring]

as above check the car is charging and also switch you multi meter to amps and check for a current drain

 

ammeters must be fitter in series , so remove a lead and fit the meter between the lead and the battery

 

Yes, but please be careful doing that - to be honest a multimeter in series on car electrics isn't a good idea - the alternator alone is more than capable of taking out the 10A fuse on the current range. Amps go both ways and while the car is running, the battery will be being charged under most circumstances.

 

You really can't add a current loop to a car that's running, it means disconnecting the battery while the car is running and inserting the meter in series You'd need to ensure the alternator had a bit of load on it first before attempting this - for someone not completely confident with electrical systems and in particular, low voltage high current systems, better not to do this.

[KernowCooper]

A good clamp meter that does DC Amps is the way to go, except the cheap ones only do AC Amps and the DC ones may be to expensive for home use

[Captain Mainwaring]

A good clamp meter that does DC Amps is the way to go, except the cheap ones only do AC Amps and the DC ones may be to expensive for home use

 

 

Very few good cheap ones about, in fact very few DC clamp meters about full stop, for obvious reasons. Many years back my ex boss had a tin little clip on one that only read DC amps, where the hell he got it from, I don't know, but it looked cheap but effective and would probably sell well.

[Captain Mainwaring]

Hmm...they got cheaper - not a bad meter for the part time automotive mechanic....

 

http://cpc.farnell.c...7226-tenma.html

[Doovydoo]

Ok, so my readings on the fully charged batter are:

 

Battery out the car -  13.34v

 

Battery in the car, car off  - 13.31v

 

Battery in, car on - 12.28v

 

 

 

So I'm thinking new alternator time.. earth connections seem good too.. although I have gone new on the way in case. How tight is the alternator belt meant to be - someone on the TMF facebook page says if it's too tight it could case the voltage drop as not running round fast enough - and that I should be able to turn it by hand.. I don't think I can do that so it may be a bit tight?!

So many options

[KernowCooper]

Those readings are not after the batteries been standing for 4hrs + though,  12.65v is fully charged and with yours in the car and car on I assume you mean ignition not running that battery voltage is low, now start it up and run at 2000rpm and take a reading it should be be between 13.7-14.2v if the alternators ok.

 

And thats laughable whats on facebook and not correct, if you can turn the alternator by hand with the belt on its to loose look for a deflection on the long side of approx 12mm.

 

Do the test with engine running and see if you have 13.7-14.2v if so the alternators charging, let batter stand a full day test voltage and see if its

 

12.65v =100% charged

12.45v = 75% charged

12.24v = 50% charged

12.06v = 25% Charged

11.89v = 0% Charged and Flat.

[Doovydoo]

Those readings are not after the batteries been standing for 4hrs + though,  12.65v is fully charged and with yours in the car and car on I assume you mean ignition not running that battery voltage is low, now start it up and run at 2000rpm and take a reading it should be be between 13.7-14.2v if the alternators ok.

 

Sorry, I meant when it's in the car connected up with the car running at idle, it was at 12.28v. Will try again at 2000rpm and see..!!

It will have been sitting for more than 4 hours when I test again tonight. Cheers!!

 

 

and will look for about 12mm of play in belt too.

Edited by Doovydoo, 15 July 2013 - 10:30 AM.

[Bungle]

 

as above check the car is charging and also switch you multi meter to amps and check for a current drain

 

ammeters must be fitter in series , so remove a lead and fit the meter between the lead and the battery

 

Yes, but please be careful doing that - to be honest a multimeter in series on car electrics isn't a good idea - the alternator alone is more than capable of taking out the 10A fuse on the current range. Amps go both ways and while the car is running, the battery will be being charged under most circumstances.

 

You really can't add a current loop to a car that's running, it means disconnecting the battery while the car is running and inserting the meter in series You'd need to ensure the alternator had a bit of load on it first before attempting this - for someone not completely confident with electrical systems and in particular, low voltage high current systems, better not to do this.

 

 

you won't find the current drain with the engine running

 

test for the drain with the engine switched off just like it will be over night