Battery/alternator

Hi guys, after a bit of help with a problem I'm having. 2.5na running a good size battery, trouble being is battery reading 12.40 on multimeter, when i go to start it (usually on jump leads as its never enough on its own) the reading does climb upto 13+ but only at high revs, when i go to put lights & heater on it drops to 11.40. I would be one happy chappy if this gets sorted. Cheers

First thing I would do is put the battery on an overnight trickle charge and then check its voltage and see if it will start the engine.

Voltage should rise to 14V , with mine fully loaded voltage drops to 13.3V then gradually rises. Switch the loads of and it will go to 14V then settle back to 13.8V as the alternator regulator catches up.[My voltmeter is a digital and quite accurate checked against a Fluke meter]
Fully charged battery should read around 12.6V

Blackburn said:

Voltage should rise to 14V , with mine fully loaded voltage drops to 13.3V then gradually rises. Switch the loads of and it will go to 14V then settle back to 13.8V as the alternator regulator catches up.[My voltmeter is a digital and quite accurate checked against a Fluke meter]
Fully charged battery should read around 12.6V

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Had 12.60 after battery had an over night charge. Should i be seeing it rise as engine is ticking over?

tottot said:

First thing I would do is put the battery on an overnight trickle charge and then check its voltage and see if it will start the engine.

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Hi, tried all that and yeh it does work on initial start up, providing its not freezing out, otherwise its jump leads out again

I would not expect to see much happening at tickover. It may be worth going over battery to starter and earth connections. Could be that battery and/or starter motor are a bit tired.

tottot said:

I would not expect to see much happening at tickover. It may be worth going over battery to starter and earth connections. Could be that battery and/or starter motor are a bit tired.

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Nice one, I'll give that ago. Thanks for your help mate

taylorslandy72 said:

Hi, tried all that and yeh it does work on initial start up, providing its not freezing out, otherwise its jump leads out again

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It sounds to me very much like your battery is kaput - It should hold charge for a week without issue...

IIRC, Halfrauds do a free check .... or you might find a supplier locally that will do a proper drop test.

Disco1BFG said:

It sounds to me very much like your battery is kaput - It should hold charge for a week without issue...

IIRC, Halfrauds do a free check .... or you might find a supplier locally that will do a proper drop test.

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Yeh i did think about a proper check as only done the basic one with the multimeter. Just that they cant check the alternator can they?

Old and tired battery and/or duff alternator or set-point on Alternator too low?

DanClarke said:

Old and tired battery and/or duff alternator or set-point on Alternator too low?

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Thanks will check over

taylorslandy72 said:

Yeh i did think about a proper check as only done the basic one with the multimeter. Just that they cant check the alternator can they?

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If they have a DC clamp meter they can ! - mind you they start at about £25 on the web .... so put it on your Christmas list

start up, trun evetything on and see if th eheadlight get brighter when you rev, if yes then alernator is ok, prpbably duff battery. If no, alterntor is duff and probably battery too.

rob1miles said:

start up, trun evetything on and see if th eheadlight get brighter when you rev, if yes then alernator is ok, prpbably duff battery. If no, alterntor is duff and probably battery too.

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That sounds an easy way to tell, will give it a go tomorrow, if it is the alternator what kind do i buy? as this engine is 2.5n/a and im unsure of the year etc.

I've just gone out and checked the belt on the alternator, to be honest i can move it up and down about 6"

Well there's your problem then,but still get the batt checked.

Hi, just an update to let the people no who commented on my post. Tightened the alternator belt and yes the reading went up to 13.20 on multimeter. Another discovery was the 2 wires from the alternator that go to the battery. I fitted a new inline fuse box about 6 months ago and only 1 of those wires were fussed, the other was in place but no fuse installed which meant it was doing nothing. Joined them both together with a 35amp fuse and ha ho it then read 13.60+ on multimeter. Still going to get battery checked tho, just for piece of mind but i am pleased with the outcome. Thanks everyone

Do you have an ign light that goes out when the engine gets going?

rob1miles said:

Do you have an ign light that goes out when the engine gets going?

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Yeh, that is the 3rd wire from the alternator, that one was right.

Like I say give your batt a good overnight charge on a mains charger. May well get it back to a usable level. Good your charging problem is solved but alternators are not good at getting low battery's back up to full charge.