Re: 12 volt power source?

On Wed, 26 Dec 2007 10:35:23 +1300, I said, "Pick a card, any card"
and Greg Procter <procter@xxxxxxxxxx> instead replied:

Ray Haddad wrote:

On Wed, 26 Dec 2007 07:34:12 +1300, I said, "Pick a card, any card"
and Greg Procter <procter@xxxxxxxxxx> instead replied:

Ray Haddad wrote:

On Mon, 24 Dec 2007 11:21:58 +1300, I said, "Pick a card, any card"
and Greg Procter <procter@xxxxxxxxxx> instead replied:

It's fun arguing with Ray because he seems to have it in for me, but I'd
rather real people like you kept the context in mind when getting
involved.

I don't have it in for you at all, Greg. I feel that there is a need
for folk like you who are always wrong. Someday, you will suffer the
fate of most Darwin Award winners and do yourself some real harm
with all of your wacky notions.

A 12 volt battery will never be at a 13.8 volt potential. Can't
happen. Not now or ever.

Even though I cited a manufacturer's data page on their lead acid
batteries floating at up to 13.8 volts?

The nominal voltage is the one you want.

So all the other factual data is meaningless and irrelevant??? I guess
they had to fill the page with something?

It all has its uses, Greg, but not as you believe.

Yeah - well, what do the manufacturers know!?!

Greg, do you know what that means? Clearly not. I'll try to explain.
That rating means that the battery charge voltage may be floated to
13.8 volts safely for long periods of time for keeping the battery
charged.

Go read it again - they said 14.2-14.5 volts.

Greg, that's a theoretical maximum and the 13.8 volt charge limit
has become a defacto standard. This is a red herring here. The
battery itself will not go over 12 volts. You clearly stated that
the voltage on train power supplies was 13.8 volts because that is
what a battery is. It's not. Quit trying to rearrange your own
claim. It's very dishonest, Greg.

It doesn't mean that the battery itself will ever maintain
a potential of 13.8 volts all by itself without an external charger
being applied.

Well, a small change of tack here - I originally stated that a commonly
used circuit for operating a model railway (1930s-60s) was a trickle
charger and an automotive battery - giving 13.8 volts.

For CHARGING, Greg. For CHARGING ONLY. Not for replacement of a 12
volt battery as you originally stated.

<sheesh>
With any electrical/electronics circuit, the _maximum_ voltage is
important.

For charging, yes. For eliminating a 12 volt battery, no. The
voltage that is important is the nominal voltage.

12 volt lead-acid batteries under charge do not limit
the voltage to 12 volts in the overall circuit when external
potential is applied. That's what the "floating" voltage means.

You seem bent on dying in this ditch today, Greg. Press on.

I'm on my 2nd-10th time round with every point - I've given you a
manufacturer's cite,

Which you have misinterpreted.

I've pointed out your mistakes and flawed thinking.

I'm just a lowly electronics design engineer. What would I know?

I'm a practical person rather than an theoretical engineer and I know I
make the occassional mistake, but you're talking a load of bollocks.

What, Greg? That a 12 volt lead-acid battery will actually be a 12
volt power source? That's fact, not your brand of fiction. In your
world, batteries reach any voltage you want even outside of their
physical ability.

The
figure that counts is not the nominal voltage, the average voltage, the
mean voltage, the minimum voltage, the charging voltage or the static
voltage - we were discussing the _maximum_ voltage that could be seen on
a model railway from a supply containing an automotive battery at the
time when "12 volts DC" was set as the norm (by the NMRA)

That would be 12 volts DC. Or, as pointed out by others here, a
maximum of 12.6 volts in an absolutely perfect world. Never will it
reach the 13.8 volts you suggested.

In an automotive or model railway situation the voltage at the battery
terminals and the attached loads cannot be higher than the terminal
voltage - the difference between generator/alternator/charger output and
battery terminal voltage _MUST_ be lost in the resistance of the
circuit. Voltages above 13.8 volts applied to battery terminals will
result in high currents which will cause out-gassing and heating of
battery plates with consequent distortion and probable destruction of
the cells - but what do _I_ know.

So, you can be educated after all. It has to be beaten in, but you
can be helped.

Regards and a Merry Christmas to all!

The same back at you, Greg.
--
Ray
.

Relevant Pages

  • Re: 12 volt power source?
    ... and Greg Procter instead replied: ... 12 volt battery which is never, ever going to be at 13.8 volts. ... The battery is in circuit between the generator/alternator and the load, ... it's an integral part of the voltage regulation circuit. ...
    (rec.models.railroad)
  • Re: Outboard Motor Charging System.
    ... >>> Since the terminal voltage of a good lead acid 12 volt battery doesnt ... >>> missing in the description of the voltage. ... >>> terminal voltage might go as high as 17 volts while the battery ...
    (rec.crafts.metalworking)
  • Re: 12 volt power source?
    ... and Greg Procter instead replied: ... 12 volt battery which is never, ever going to be at 13.8 volts. ... The battery is in circuit between the generator/alternator and the load, ... it's an integral part of the voltage regulation circuit. ...
    (rec.models.railroad)
  • Re: voltage low on car battery
    ... What is the CHARGING voltage at 2.5 amps after several hours? ... A typical auto battery these days has six cells each, nominally, 2 ... Hence such systems are called 12 volts systems. ... Also one bad cell in the series of six can spoil the battery. ...
    (alt.home.repair)
  • Re: voltage low on car battery
    ... What is the CHARGING voltage at 2.5 amps after several hours? ... A typical auto battery these days has six cells each, nominally, 2 ... Hence such systems are called 12 volts systems. ... Also one bad cell in the series of six can spoil the battery. ...
    (alt.home.repair)