DC 12 volts to DC 9 volts??????

Saw two cells off it.

thanks

The original post was referring to a 12V lantern battery.

Still, if the OP needs a regulated 9 V output, then the diode method might not be good enough, and some type of regulator might be required. 7809?

But if the OP just needs 9V, more or less, then the diodes should work fine.

--Mac

How much current do you need? How well regulated does the 9V have to be?

Or, if you don't know, then what are you going to do with the 9V?

--Mac

Four 1N400x diodes in series with the battery, that is 4 x 0.7V = 2.8V drop.

Before you do this, make sure tthe 12V is really 12, and not something like

14.5, which is what you would get in a car.12V power supplies sold for use with 2 way radios are set to 13.8. Even 8 new dry cells would be about 12.8. I vote for an LDO series regulator.

Tam

If it is a lantern battery as stated, the maximum voltage using 8 internal Alkaline cells would be 12.48V. A fresh Alkaline cell usually gives 1.56V so 8 x 1.56V would give 12.48V. This would give 9.68V after the diodes, still acceptable. But I agree that a voltage regulator, preferably a low dropout regulator could be better in some cases.

M.S.

Yeah, I saw that the first time I read this, then forgot. Problem with a constant voltage drop is that if 12V gives you 9, then 10V gives you 7, whereas with the LDO anything over about 9.5V will still give you 9 out. Check out national.com.

Tam

The *simplest* way would be a linear voltage regulator like a 7809.

It won't regulate the 9V output as the battery gets exhausted though. A switching regulator is more complicated but is better in this respect.

Graham

saw off the top 1/4th.