R

redrange

New Member
anyone know what voltage i should have at the battery when engine running?
i have 13.5v at batt and i think that a little low!! 13.8v at alternator output cable.
battery is only 3 or 4 months old but it seems a little slow when starting from cold!!
anyone got any figures?

thanks in advance..

p.s. its the r/r in my sig!!
 
13.5 is fine in my opinion. Without wishing to patronise you if you consider your battery to be a reservoir of water, the height of which is 12 inches and have another reservoir which is connected via pipe with a level of 13.5 inches then the original reservoir will be topped up without any problem. Anywhere between 13.2 and 14 volts is generally acceptable. Have you tried the same test under load? Try it again with heater and lights on. If you receive a similar value then all is well.

Hope that helps.
 
Courageous said:
13.5 is fine in my opinion. Without wishing to patronise you if you consider your battery to be a reservoir of water, the height of which is 12 inches and have another reservoir which is connected via pipe with a level of 13.5 inches then the original reservoir will be topped up without any problem. Anywhere between 13.2 and 14 volts is generally acceptable. Have you tried the same test under load? Try it again with heater and lights on. If you receive a similar value then all is well.

Hope that helps.
Click to expand...

thanks for that but i have since found that im looking for 14.2 idealy if not more. new 120amp alternaor is £95 so not the end of the world. will double check tomorow but think its on the cards....

thanks again though.
 
had a day on looking into this and im after 14.2 to 14.8 volts, anything less isnt good enough, and bearing mind the battery is 13.2 volt you can see why! anyway a 120 amp alternator can be picked up for £95, not bad........
 
Why stop at the 120amp, With all the toys on your HSE and this being winter, I'd see what a 150amp costs. Looked at mine the other day, and although I never checked the voltage its rated at 150amp.......................so aren't I the lucky one!!!!!!!!!
 
Dorset VogueSE said:
Why stop at the 120amp, With all the toys on your HSE and this being winter, I'd see what a 150amp costs. Looked at mine the other day, and although I never checked the voltage its rated at 150amp.......................so aren't I the lucky one!!!!!!!!!
Click to expand...

150amp .....what accesories do you have in your car, a Tig welder!!!:D
 
Geekfreek said:
150amp .....what accesories do you have in your car, a Tig welder!!!:D
Click to expand...

Some of the bigger Merc vans have 150amp alternators and I've been told their an easy swap. Haven't seen or done this swap me sen so can't vouch for the info. but it's worth a visit to a breakers to find out.
 
Can check the part no. on mine if you want and post back if its of any use. I'm sure its a 'standard' item either maked LR or Lucas.
 
well i was going to run till hot today then check the voltage output at rear of alt and alt body for earth.........

all did not go well as it was dead!! g/box fault, srs fault, abs fault then the alarm sounding then keycode lockout! all down to the 5 month old battery being knackered.
changed that and all is well again but for 13.9 to 14.1 volt at alternator still!!
one fault has been diagnsed and rectified but.........
should i renew alternator? be piece of mind but £100, think i will?

what would you guys do?

edit, i brought it anyway! best be safe than sorry.........a wise man once said!
_________________
 
Have you tried just removing the cables and cleaning all the contact surfaces at both the alternator and battery? Any resistance there wil lead to a volt drop occuring.
 
micko2602 said:
Have you tried just removing the cables and cleaning all the contact surfaces at both the alternator and battery? Any resistance there wil lead to a volt drop occuring.
Click to expand...

yes i have as it goes, the earth cables from battery and engine where they bolt onto the chassis was very loose, i still only have 13.9 volt across back of alternator and body of alternator using digital mutimeter!
 
Have you tried checking the voltage with the engine at idle and at say 2000rpm to see if this makes any difference? Also what have you got switched on when you do this? If you can get your hands on a clamp on ammeter you could see what current you are pulling, it may be that there is something else pulling a bit of load.
 
the AA man who jumped me had a clamp on amp meter and reconed it should have been showing many more amps than it was. i cant remember exactly how many it was now, i think maybe 15 or so, AA man reconed should have been more like 30 with battery in that condition.....anyhow new alt tomorrow hopefully, its been fine today with just the battery but how long for?
 
new alternator fitted and voltage at battery is up to 15.2 when its just been started from cold, im very happy.....
 
Hi there, been racking the grey stuff on this one - trained as an autoelectrician 20 odd years ago. Lucas alternators should be charging anywhere from 13.6 to 14.2 volts. Hope this helps. Cheers, Ian.
 
I agree Ian - my training in engineering stems from 1975 and 13.5 volts (given an acceptable tolerance in multimeters) to me would figure as acceptable. Ok my analogy used 12v instead of 13.2 as redrange quite rightly stated but the principle still remains - 13.5 volt will top up a 13.2 volt reservoir. Obviously a 14-15 volt one is going to do it quicker but there is a risk of overcharging too! I'd still have liked a reading under load as requested but he's happy now anyhow so all's well!
 
Courageous said:
I'd still have liked a reading under load as requested but he's happy now anyhow so all's well!
Click to expand...

sorry guys, i forgot all about you....... how rude! il get you one if you want but it will be with new alternator!!
the old one was at times 13.3 at battery, even though it may charge it up it was way too low.
 
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