Correct Battery Voltages, Revisited

[MrAl]

Hello there,

In the past years I had been dealing with battery voltages when the car is charging that I would think would be too low to properly charge a car battery. These was not just the case with the Volvo 1998 v70, but also with my old 1988 Hyundai.
Why do I think this. It's because I have measured other cars (other makes, models, not the same makes and models as above) and their charging voltage is well above 14 volts, while the Volvo was always around 14 volts and no higher, or maybe a tiny bit higher but not more than 14.1 volts ever, and usually just 14 volts, and as the battery charges that goes down too, 13.9 volts, 13.8 volts.

That means that something is not right. I don't think it was just with this Volvo either, but others of that same year, and maybe more years also.

I measured these when the car is just started up after a cold sit overnight:
Chevy 2003: 14.5 volts
Ford 2001: 14.4 volts
Buick 1998: 14.7 volts
Volvo 1998 v70: 14.0 volts
Hyundai 1988: 14.0 volts

This makes it plain to see that the Volvo voltage is lower than any except for the old Hyundai.
I thought it might be related to the year the car was made, but the Buick is also a 1998 and it's starting charge voltage is much higher.

Any thoughts on what is going on? Could it be because of alternators or voltage regulators that are not working right anymore, or maybe the wiring resistance went up too much (which can cause this because the voltage regulator is remotely located away from the battery by around 2 feet or so).
I know one problem is the ground terminal on the alternator can be less than tight. With the Hyundai, I had to tighten the main bolt of the alternator as tight as I could get it in order to even get that 14.0 volts. If it was not super tight, I would get even less charging voltage at the battery terminals.

[abscate]

These are small, 5% differences in the design voltages of the charging system. It may be the Volvo alternator output current is higher than these other models, so you can return charge faster at lower voltage.

I don’t think the differences mean there is an inherent problem.

[Sveedy]

Agreeing with abscate. This is just due to different manufactures cars / systems. 13.9 - 14.1 is normal, for these cars.

[MrAl]

Agreeing with abscate. This is just due to different manufactures cars / systems. 13.9 - 14.1 is normal, for these cars.

Hello,

Well 'normal' doesn't necessarily mean 'good'. That could be part of the whole point.
The problems i had with the Volvo and Hyundai charging told me something was wrong long ago. That's what made me look into this so intently.

[MrAl]

These are small, 5% differences in the design voltages of the charging system. It may be the Volvo alternator output current is higher than these other models, so you can return charge faster at lower voltage.

I don’t think the differences mean there is an inherent problem.

Hi Steve,

Well from what I have found in the past, the charging voltage is very critical. To get the battery fully charged, the voltage has to be high enough to get current to pass through the internal resistance, which goes up with age. I know that 0.7v does not seem to mean that much around 14 volts, but it could make all the difference in the world. That's what makes me concerned about this. It could be a general whole class thing, where batteries are not being made as good as they used to be. After all, who would question it if it seemed 'normal'.

One battery I had I used to charge with a heavy duty power supply that could put out 10 amps at 30 volts if needed. I used to turn it up to almost 15 volts to get the battery to work right after some time.

It may be true that some batteries can take current better at 14v than others, but from what I have seen now with several cars that behavior does not last very long. Eventually, and it could be just a few months, they start to need a higher voltage. It is then that the extra small difference means the battery charges all the way or just part way.

I wonder if anyone would even notice this. If they go to work every day and the car starts every time and the battery lasts for 3 years, are they going to argue with that. For people that don't go to work every day but only drive maybe once every three days, it could mean that the battery runs down too low over a short time period.

Is it any wonder that i had to connect up the solar panel to the Volvo.

So far the general consensus here is it seems 'normal' to charge at 14.0 volts, and that is probably because they didnt have a problem yet.

Also, note that some people on the web have now talked about altering their alternators with that series diode pair fix. It forces the charge voltage to be a little higher, maybe just 0.5v, but they do it. It involves getting the alternator and/or voltage regulator off of the car to work on it though, so for some cars this can be a big job.

What else i suspect is that a lot of people are able to start their car with a battery that is not fully charged but maybe as low as 50 percent. That would still start the car, so they may not notice anything. I found that i was able to start the Volvo with a voltage as low as 11.8 volts. That's far, far too low for a car battery, yet it started. Come winter though it may be a problem.

What i am after i guess is to understand this to the fullest extent. That may be hard to do though because it's kind of hard to test the state of charge of a car battery especially while it is still in the car.

[dikidera]

A couple of threads ago a user was also bothered by this and he went and gave the connectors a grind until they were shiny and saw an immediate improvement. Not just at the alternator, but fuse box too.

[scot850]

Alternator and starter cable resistances and bad grounds also affect charging capacity. I once asked the question of a Master Volvo mechanic I trust. He answered anything above 13.5V is good. The bigger issue is giving the car time to recharge after a start. My wife had an 99 Audi A4 that regularly would get starting issues in the winter. She started the car and ran it about 2-3km to the station and back in the winter. Naturally, all the charge drawing items were on. Lights, heated mirrors, rear screen, heater at full blast, heated seats on. It was hardly surprising at -30C it would struggle after about a week of these runs. That was when I first bought a trickle charger over here.

Neil.

[MrAl]

Alternator and starter cable resistances and bad grounds also affect charging capacity. I once asked the question of a Master Volvo mechanic I trust. He answered anything above 13.5V is good. The bigger issue is giving the car time to recharge after a start. My wife had an 99 Audi A4 that regularly would get starting issues in the winter. She started the car and ran it about 2-3km to the station and back in the winter. Naturally, all the charge drawing items were on. Lights, heated mirrors, rear screen, heater at full blast, heated seats on. It was hardly surprising at -30C it would struggle after about a week of these runs. That was when I first bought a trickle charger over here.

Neil.

Hi there Neil,

Well I think a trickle charger is a really good idea for these cars, maybe many types of cars.

I hate to say this because I don't want to dissuade anyone from taking advice from known good people, but there are some differences between a "master mechanic" and an electrical engineer.
A master mechanic will have good knowledge of vehicle operations and some knowledge of electrical systems. An electrical engineer will have good knowledge of electrical systems and some knowledge of vehicle operations depending on his or her specialty.
An electrical engineer who specializes in battery charging systems and related would be the person to ask. Perhaps a battery manufacturer who is not afraid to tell the truth about the batteries it makes.

I guess we do have to be careful who we ask because different people have different experiences and they would provide information based on those experiences, not necessarily on scientific fact. Then again as i was saying before, it's hard to tell sometimes what is actually working right and what is actually working just OK or just because of certain habits that favor a system that is not even working correctly. That is, a system that is not working right may seem to be working right just because of the habits of the owner and their opinion of the system function.

I can tell you one thing is absolutely certain. If you don't drive much, 14.0 volts is not enough. I've proved this with two vehicles now. That is however assuming that batteries are still made well.
With the Hyundai I had to bring the battery into the house to charge about once every three months, and that charge voltage was also 14.0 volts, and the battery was not even a year old yet. With the Volvo I had to install a solar panel charger with enough power to charge the battery effectively every time the sun was shining.
I also suspect that many owners out there right now have batteries in their cars right now that are not fully charged. They may be 50 percent, 60 percent, 70 percent, etc., but i suspect they are not all the way to 100 percent or near that. This can still work because in many cases the car will still start up and it will seem like everything is normal. This is probably why so many batteries fail in winter and not in the warmer months.

The conclusion therefore I would have to say is if something works for you then I guess you can stick to it. I had to investigate because I am an infrequent driver who sees the battery voltage drifting down farther and farther over time unless I charge it with another method or drive all over the country (ha ha).

One person who has a mechanic friend said that this friend said that "you have to drive the car". I thought that was sort of funny because who wants to drive their car for the sole purpose of charging the battery. What, I am supposed to drive around the block 100 times just to charge the battery ... I don't think so (ha ha).

We also come to the idea of just starting the car every now and then to keep the battery charged. This would mean staying in the driveway with the engine running.
The problem here is you have to keep it running long enough to properly charge the battery, and I don't think 14.0 volts will do this well enough either.

I also think that maybe the in-car battery drain is enough to cause a problem too, even though it is a small drain current. I say this because I can keep a battery for a Volvo inside my house for three months and it still measures above 12 volts. That would not happen if it was installed in the Volvo. Maybe even a 5ma current draw is enough to drain the battery down significantly over several days.

I'll be looking into this more and more as time goes on. If I can find anything else out about this I'll yell.

Oh BTW, I asked another seasoned mechanic who has been around for at least 25 years before he sold his station recently. I needed a jump one day (no surprise there) and he came over and I told him I think the battery is not being charged enough because the charge voltage is too low. He replied that "you don't want to cook the battery".
While that's true, if you only go on short runs you wont cook the battery, but he did not take my drive habits into account. Yes, you don't want to cook the battery, but you also don't want it to go dead and not start the car (ha ha).

[MrAl]

A couple of threads ago a user was also bothered by this and he went and gave the connectors a grind until they were shiny and saw an immediate improvement. Not just at the alternator, but fuse box too.

Hi,

Oh that's very interesting. That shows that we should do a "voltage drop" test on all the wiring and connectors. This would mean measuring the voltage drop across all the wires related to the battery charging system. That may point out the problem component. The trick is to get enough current flowing to do the test properly.

[Sveedy]

Agreeing with abscate. This is just due to different manufactures cars / systems. 13.9 - 14.1 is normal, for these cars.

Hello,

Well 'normal' doesn't necessarily mean 'good'.

Took my temperature today, and it was......normal. Hmm. Guess now I have something else to worry about.