Battery SOS

Post by **GeorgeHurst** » Mon Dec 14, 2009 10:56 am

Hello,

I have just tried starting my car and for the third time in a week I have a flat battery... I have jump started it the first two times and then taken it for a drive for over an hour to make sure it charges fully.

It was dead yesterday, took it for a 1hr drive and then today it is dead again!

I checked to see if it was charging after jump starting it and the voltage fluctuated between 12V and 14V with lights on and off (which means it is charging I believe?)

The fan belt is fine as far as I can see, the battery was bought new 6 months ago and the dynamo was new about 3 years ago... any ideas?!

Alternator conversion is next on my list, but maybe this is a sign of a dead battery?

Any help greatly appreciated!

George

Post by **alanworland** » Mon Dec 14, 2009 11:30 am

Or is something being left on?
Remove earth lead from battery and with nothing switched on there should be no current flow when a ammeter is connected between the terminal and the removed lead. (there might be a few mA flowing, but this would not cause what you have experienced)
If there is remove the fuses one at a time to try and identify where the current might be going.
Or yes, you could have a duff battery - where you got it from should be able to do a battery discharge test.

Post by **mike.perry** » Mon Dec 14, 2009 5:28 pm

Have you still got the guarantee?

Post by **rayofleamington** » Mon Dec 14, 2009 5:36 pm

It's worth checking for current drain, as this is sometimes an issue.
Other than that it's usually easier to charge the battery overnight - it will need to be charged to test the battery anyway.

If you can find a decent garage (or starter motor/alternator/battery specialist) they can do a high-load test on the battery. This will tell if the battery capacity is ok or not.

With a dynamo, you'd need to rev the engine to see if it's charging correctly, as they are weak at idle speed. You should see 13.5 to 15 volts at higher revs, with the lights on or off. If you see over ~16v, then it's overcharging and may have damaged the battery (the same applies to Alternators).

Post by **bmcecosse** » Mon Dec 14, 2009 8:27 pm

Hmm -you say 12 volts with lights ON - and 14 volts with lights OFF ? This suggests a fault with the charging - it should 14 volts with lights ON and OFF! First step - is the fan belt really tight enough ?

Post by **rayofleamington** » Mon Dec 14, 2009 9:02 pm

it should 14 volts with lights ON and OFF!

not with a dynamo and a slow idle speed - hence my comment to check it with higher revs.

Post by **GeorgeHurst** » Mon Dec 14, 2009 10:28 pm

Thanks for all the comments everyone.
I don't have the means to test myself (the test I mention was done by the F.J. breakdown mechanic who jumpstarted, couldn't find anyone to give me a jump so had to call!) As such I think I'll have to take the battery to the garage for a test, I have another battery also so will do an overnight charge on both and take them both down.

Alan/Ray - I don't think there is anything being left on, the only thing I think it could be on that front is my stereo taking a small current to keep its time up to date, though I always turn the main power off when not in the car...

Mike - I think I do have a garauntee but I bought the battery miles from where I live from a small factor, so I don't know if I'll ever be back there!

Roy - Fan belt is really pretty tight, a very small amount of slack if I press it hard, but I think this is simply the fact that it is flexible by nature...

Post by **bmcecosse** » Tue Dec 15, 2009 8:20 am

There would be absolutely no point testing a dynamo at idling speed!
Yes - the fan belt is not meant to be 'bow' tight. Best I can suggest is to check all connections are tight - and get hold of a small voltmeter - Maplins or similar.

Post by **GeorgeHurst** » Wed Dec 16, 2009 1:13 am

Thanks for that Roy. I've been reading other battery related threads on here and connections seem to be a common problem so will double check everything is sound. When you say voltmeter, I presume you mean a multi meter, or would that not do the trick?

Post by **rayofleamington** » Wed Dec 16, 2009 9:45 am

When you say voltmeter, I presume you mean a multi meter, or would that not do the trick?

Yes - any ordinary multimeter will be fine to measure volts. Once upon a time a multimeter was a rare item, and a 'voltmeter' was much cheaper... The term 'voltmeter' is often used in place of 'multimeter set to read volts' as it trips off the tongue a lot easier.

Post by **GeorgeHurst** » Wed Dec 16, 2009 10:37 am

Ok great, I thought as much, thanks for clarifying Ray.

I have now been down to a local garage with my spare battery fitted (which was charged over night) and the voltages at a fast idle read ~14V, and ~13V with the lights on. It reads ~12V at slow idle, but as stated above I understand this is natural. They also did a high load test on it and it was fine.

It therefore appears to be charging correctly, so I can only assume that my 6 month old battery is a duff one. I have it on charge at the moment and will take it down to the get it checked too. Now I need to try and find the guarantee!

Many thanks for the help, very helpful as usual

Post by **bmcecosse** » Wed Dec 16, 2009 2:54 pm

Unless you have just been running around on short trips - with lights/wipers/headlights/heater ALL on ! 13 volts with lights on at fast idle doesn't sound too great - check again with just about everything you can switched on and see what happens. The headlights are supposed to be wired through the A1 terminal on the Reg box - this pulls a higher charge from the dynamo when they come on. Any chance the wiring has been messed about ?

Post by **GeorgeHurst** » Wed Dec 16, 2009 4:45 pm

Thats the thing, I've been doing LONG trips... up to 3 and a half hours at times!
The wiring may well be messed up... when I got the car there was insulation tape and wires not leading anywhere all over the place, I think the previous owner was something of a bodger

Will check that terminal, do you know off hand the colour of the headlight wire?
It is my intention to redo all the engine wiring when I take it out for a repaint and to fit new head etc

Assuming that the voltage is going to drop below 13V with everything on, does that suggest a knackered dynamo?

Post by **bmcecosse** » Wed Dec 16, 2009 5:16 pm

See Barry's diagram at the top of this section - worth printing off a copy to carry in the car. It's the brown + blue wire that should lead to the lighting switch - and should start from the A1 terminal. I would say 13 volts is just about ok - but i wonder if it falls even lower when other things are switched on. I assume you don't have an ammeter? If not - add it to your Christmas list to Santa!

Post by **GeorgeHurst** » Wed Dec 16, 2009 5:26 pm

Thanks for that, will check it tomorrow morning in the light. Yes I wonder too if stereo, wipers, heater and lights will make it drop even further.

I don't have an ammeter, though my Christmas list already consists of LCB, alternator, halogen lights and more Autoglym products than I can list!! Might be a present for myself

Post by **bmcecosse** » Wed Dec 16, 2009 5:28 pm

Well - alternator will likely sort this out anyway. I doubt there is a problem with the battery.

Post by **GeorgeHurst** » Wed Dec 16, 2009 5:33 pm

Yes hopefully! Battery seems to be fine according to the test

Post by **morrisminormad** » Sat Dec 19, 2009 7:34 pm

it could be a problem with the voltage regulator