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13,8 V idling charging voltage ok ?

850 TDI automatic 1996 with 265.000 km

Last year in summer 2008 before a trip through countries with sparse Volvo-support possibilities I had my mechanic change the brushes-regulator-unit of the alternator at about 240.000 km kilometrage. I was a bit under time pressure so he could get hold only of one from a Volvo dealer, cost about 100 Euros more than from a "normal" shop, though probably the same product. I had bought the car with about 210.000 km kilometrage and had no idea whether the unit had been changed before. I did not want to get stuck because of worn brushes. Befor winter I changed the battery - put in a new 75 Ah unit.

Now during summer I have the Eberspächer engine preheater on for about half an hour in the morning, drive to work about 1 hour 80 km, then back home without engine preheating the same distance, headlights low beam on during driving, air condition fan, too. In my opinion that driving should be enough to charge the battery after the engine preheating current loss in the morning. I was curious how "charged" my battery actually was and connected my home charging unit, 10 A max output. I was surprised that it took about 2 hours charging until the charging current dropped to zero, did not measure voltage, but supposedly

14,something Volts.

So I decided to check the voltage at the battery terminals - according to Haynes manual it should be 13,5 - 14,8 V during engine operation. The reading was at idle rpm without anything turned on - 13,8 V, after turning on the headlights

13,7. When turning on all possible stuff - seat heaters, back window heater, fan, high beam light etc, even with highers rpms the reading dropped to 13,4 V.

I tried to increase my wisdom on battery charging voltages:

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V would just fit the 2,3 Volts, but still is the lower limit. Do I have a faulty regulator unit or does it behave as it should even at the expense of submaximal battery capacity? Any other comment on the values measured? Any other check I should do?

Franz47

Reply to
franz47
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"franz47" schrieb im Newsbeitrag news:h6uask$gia$ snipped-for-privacy@news.albasani.net...

In our family we have another Volvo: 745 TD 1989 - I just checked the idle voltage - 14,5.

Franz47

Reply to
franz47

Hi, mine is 850 TDI, manual, 11/1996, 373.600 km.

Last time I was checking the voltage was during last winter at -6 C.

Radings were the following:

-battery itself -- 12,45 V

-preheating glow plugs on -- 11,25 V

-moment of ignition/starting the engine -- 9,80 V

-idling at 1100 rpm -- 14,15 V

-idling at 850 rpm -- 14,26 V

-idling with lots of stuff -- 14,03 V

Srry, I don't know if your regulator is OK, but 13,8 V seems a little bit low. Check the battery terminals and clean them, also check the main cable if its corroded...

Good luck!

Reply to
HAL9000F

It is perhaps a hair low, but I would consider 13.8V to be perfectly reasonable. If it's too high, the battery will overcharge while you drive as it is constantly connected.

Reply to
James Sweet

"HAL9000F" schrieb im Newsbeitrag news:h6up3p$675$ snipped-for-privacy@ss408.t-com.hr...

Sounds reasonabler than my values. Maybe I threw the old battery out prematurely.

Everything is fine there, lubricated with the proper stuff. I actually put the meter´s pins onto metal parts of the cable, too.

I think I will change the regulator again.... Franz47

Reply to
franz47

"James Sweet" schrieb im Newsbeitrag news:h6vhgk$cpb$ snipped-for-privacy@news.eternal-september.org...

My other Volvo, the 745 has a battery (brand Hoppecke - unfortunately they quitted to produce car batteries some years ago) for many years working fine with the higher charging voltage. I do not use theis745 during the winter, keep the battery in the basement with a timer switch attached to a battery charger for 15 min every day. The charging current drops at a voltage above 14 volts with this charger.

Sulfatation is described as a consequence when the battery ist stored not completely loaded for extended time. So that is what I am afraid of. The old battery which I replaced was only about 3-4 years old. It had been bought by the previous owner, he kept the car well in my opinion.

I think I will ask people at a local Volvo forum to measure the voltage on some

855s before buying a new regulator

Franz47

Reply to
franz47

Also are you checking the voltage on the output terminal of the alternator? There may be a bad connection somewhere if it is low elsewhere.

Reply to
James Sweet

"James Sweet" schrieb im Newsbeitrag news:h74shv$qcn$ snipped-for-privacy@news.eternal-september.org...

Good idea. Quite difficult to get there. I had a look today, no nut visible at the alternator terminal, everything insulated. How would I get access there to the terminal? BTW is it necessary to remove the whole alternator to change the regulatur-brushes unit? Franz47

Reply to
franz47

"James Sweet" schrieb im Newsbeitrag news:h74shv$qcn$ snipped-for-privacy@news.eternal-september.org...

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this battery has a "magic eye" visible through a window in the cap of one cell. Should be green when battery fully charge - shows green also. So everything is probably ok anyway and maybe the external battery charger overcharges. The cheapest German made alternator available would drain my pocket by about 300 Euros. The new battery was about 100 Euros. So I will go ahead without doing anything and just regularly check the battery voltage, bull eye and idling charging voltage. Franz47

Reply to
franz47

"James Sweet" schrieb im Newsbeitrag news:h74shv$qcn$ snipped-for-privacy@news.eternal-september.org...

As usual James is right!

I took the time now to have a closer look. The voltage at the alternator terminal was 14-14,1 Volts, exactly as it should be according to the regulator specs. There is a 0,3 V voltage drop between the alternator terminal and the cable terminal at the battery.

Although I removed the cable from the alternator terminal, sprayed it with electrical contact spray, cleaned it with fine sandpaper, the same with the surface of the nut pressing the cable terminal to the alternator terminal - nothing changed. The cable terminal on the alternator is connected with the cable in a way I cannot do much about. Maybe there is a resistance. On the battery side the cable turns into a terminal without much to do either. The voltage drop is already at the battery cable terminal. There is no more voltage drop between cable terminal and battery terminal. The cable disappears form the alternator into the depth of the space - is there a connection at the starter which could be the culprit?

Franz47

Reply to
franz47

There will always be a voltage drop over a length of conductor when there is current flowing, The drop (V) depend on the current (A) and the resistance (Ohm). Do not forget the negative part of the cirquit. I am not familiar with all Volvo solutions at the alternator end, but at the battery end we have the cable from the negative battery terminal to the ground (chassis or transmission). That should be checked at both ends. And for the positive part you probably could run an additional cable directly from the alternator to the battery terminals, that is what the experts did on my Toyota. Any comments James ?

Asbjørn

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Asbjørn

"Asbjørn" schrieb im Newsbeitrag news:h799sg$s2j$ snipped-for-privacy@news.eternal-september.org...

I did not measure current to the battery plus, then I could calculate the resistance. 0,3 V voltage drop still eems to be quite a lot for a thick copper cable connection of such a short distance. I will measure on another car.

I could measure a voltage of 0,3 Volts between positive alternator terminal and positive cable/battery terminal at the battery. Any resistance on the negative side of the circuit cannot influence this result.

I think I will have a look at a possible connection at the starter between alternator and battery, if it is accessible from above.

Franz47

Reply to
franz47

There's a black cap that pops off the back of the output terminal where the big red wire attaches.

Depends on the car, 740 you can easily change the brush pack/regulator with the alternator in place. Most 240s you can too, but the turbos are a lot tighter down there.

I've never had to replace the alternator itself, they're quite dependable.

Reply to
James Sweet

0.3V is not very much given the current potentially involved. The wire does connect to the starter, along with another wire that goes to the battery.
Reply to
James Sweet

The connection at the starter should be accessible, you'll have to refresh my memory as to what sort of Volvo this is. You also might see if you can get a probe in to the exposed copper wire immediately before the terminal and measure between that and the terminal to see if you have a bad connection there.

Reply to
James Sweet

"James Sweet" schrieb im Newsbeitrag news:h7afb0$uq2$ snipped-for-privacy@news.eternal-september.org...

855 TDI 1996 December (in VADIS I find it only under 1997) with D5252T MSA 15.7 diesel engine and AW 50-42 automatic transmission.

Franz47

Reply to
franz47

"James Sweet" schrieb im Newsbeitrag news:h7af57$uq2$ snipped-for-privacy@news.eternal-september.org...

Thanks for the tip. I found that, when I had a look yesterday under better illumination.

In the 855 one has to pay the price for front wheel drive and engine mounting 90 degrees to driving direction. I still have another 745 TD 1989, which I have used many years and my wife now ses in the countryside. I have changed the brush-regulator there, really a breeze. Plenty of space around the engine.

Not me either since my first car with an alternator, a Citroen 2CV in the seventies last century. Not even mechanical parts have failed. I just changed the brushes once a while in these alternators, nowadays including the regulator unit, making it much more expensive. The regulators are overpriced, for the money the tiny little, probably very primitive circuit costs, I can get a b/w laser printer with duplex unit...

Regards Franz47

Reply to
franz47

Ah, I'm not gonna be much help with specifics then, unfortunately the last Diesel powered Volvo to reach this continent was the '86 760.

I'm actually surprised I haven't heard of anyone importing an 850TDI, but I've yet to see one in the US.

Reply to
James Sweet

At least in the case of the older Bosch alternators, you could get a brush pack meant for even older ones that work with an external regulator. I've seen late 80s 700 series cars retrofitted with late 70s style external regulator. I don't know what sort of alternator an 850 uses though.

Reply to
James Sweet

"James Sweet" schrieb im Newsbeitrag news:h7aiqp$el6$ snipped-for-privacy@news.eternal-september.org...

I don´t know which kind of gas guzzlers the gasoline versions of the 850 are, but the 2,5 l Audi TDI diesel runs on about 6,5 - 7 liters/100 km (makes 36 -

33,6 mpg), which was good fuel economy at that time for that car size. Franz47
Reply to
franz47

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