12 volt power source?

Man have you asked the wrong group hehehe...

Perhaps Australian batteries have a lower voltage than the rest of the world.

BTW - I started in electronics at much the same time you did, built mr controllers in the 1960s, first computer from Electronics Australia

Regards, Greg.P.

From 12 volts down to 12 volts?

You'd prefer Wikipedia over the manufacturer's data?

The definition of "quickly" and "eventually" will depend upon the age, sulfation and acid percentage, but one could carry the new fully charged battery home from the garage, have tea and then connect it to the layout and still find a voltage between 13.8 and 13.2 volts. The following week, without use it will be at 12.6 volts. If one were to place a 12v car battery between a low amp battery charger and one's rheostat controller, a setup as has often been used in the past, there would be 13.8 volts on the track.

Regards, Greg.P.

I've used computers and PCs for layout operation for years.

Then you're wrong. They are mostly regulated. If they aren't, you aren't opening the right ones.

-- Ray

Lead-acid batteries are 2 volts per cell. World wide. Go measure yours again without the car running.

Definitely not the same as I did, Greg. If so, you'd know about lead-acid batteries, chargers and power supplies.

-- Ray

Lead-acid batteries require a minimum of 10% over nominal. That's why 13.8 volts is used to charge a 12 volt lead-acid battery. Applying any less will cause a drain after a very short time. When a battery goes way down, say to 10 volts or so from use, a 12 volt power supply will work up to a point and then become a drain on the battery. At 10% over battery rating, that's 12.0 volts plus 1.2 volts or a minimum of 13.2 volts to sustain a charge and then a trickle. Obviously, 13.8 volts fits that requirement. A unique thing about a lead-acid cell is that you really can't overcharge it unless you are dumb enough to use a constant current charger. The battery presents a smaller and smaller load to the charger as it gets more fully charged. Nature of the beast.

-- Ray

Clear your mind. That was easy. No thoughts.

-- Ray

well, I just measured 4 Australian batteries with 3 different meters, and all measurements were at least 12.5 volts - which is as I would expect from the basic electrochemistry of lead-acid cells.

Tell me, Ray, what do YOU think the exact potential is across a standard individual lead-acid cell? Are you trying to tell us it is exactly 2.00 volts?

You might like to look at some actual data at

On 12/21/2007 7:03 PM Ray Haddad spake thus:

And how do you know that? Have you cracked any open yourself?

I mean, I've opened literally *dozens* of the little buggers, and never saw a single regulator--78xx or anything similar--in any of them.

And you think that's the only kind of regulator out there? Oh, dear.

-- Ray

Yes? And?

I'm not going to quibble over a half volt. I'll leave that to the rivet counters out there. The battery is still a 12 volt battery not a 13.8 volt battery. That's close enough. If you want to continue this, go right ahead.

I'm right. You're right. So what? The point is already lost. There is no such thing as a 13.8 volt lead-acid battery. The difference of half volt variance is silly to argue over. But do press on if it amuses you. Greg will be along to huff and puff and pretend he never stated his batteries were all 13.8 volts.

-- Ray

"_All_" is irrelevant! Where electronics (or Tortoises running too fast) are concerned, the _maximum_ voltage likely to be met is the relevant figure.

I know you have to disprove everything I say, Ray, but this is getting well out of hand.

Regards, Greg.P.

On 12/21/2007 8:52 PM Ray Haddad spake thus:

No, they can also be made of discrete (i.e., non-IC) components (like transistors). But there has to be *something* there besides a transformer, rectifier and filter capacitors. So what kind of regulators do you think is in those wall warts, eh, Ray?

Greg Procter skriver:

Wouod yo be so kind to ponit me to a data sheet showing tha at lead-acid battey has a nominal voltage of 13,8 volt at full charge.

Klaus

Even a zener diode is a regulator. Play puffery all you want, David. I do know what I am discussing here while you are just guessing after opening a few wall cubes. Enjoy the game.

-- Ray

None of them are, Greg.

Not everything. Just the wrong stuff. Oh. Wait.

-- Ray

I wasn't going to push him for a reference, Klaus. Cornered beasts can be deadly. As long as he doesn't have to prove anything, he's harmless.

-- Ray