Re: Unsmoothed car battery charger - is it crap?

How long is a piece of string? With a crude transformer/rectifier one, depends on the transformer design. And the type of rectifier. And the device measuring the voltage. ;-) What matters is the voltage under load.

These days silicon diodes. Suitably heatsinked.

TMT is a troll who usually hangs around rec.crafts.metalworking

oad.

=A0 London SW

Thanks...again...what would a recommended OC voltage be for a battery charger for lead acid batteries?

TMT

load.

LOL...TMT is a poster who doesn't take crap from idiots like Michael.

Post any conservative drivel today Michael?

TMT

Depends on the charger, but usually a few percent higher than the voltage rating of the batteries it's meant to charge. It will drop under load, by how much depends on the design.

When the rectifier fails, you replace the rectifier...

Thanks.

The reason why I ask is when I was a kid I repaired a battery charger that had lost its selenium rectifiers with a couple of diodes. I seem to remember it being 14 volt something. While I would have thought it sufficient, the charger seemed to overcharge batteries from then on.

TMT

Of course it overcharges and this has already been discussed in this very thread.

The voltage drop across a modern diode is much less than that across a selenium rectifier so you have to add some resistance to reduce the current.

John G.

oad.

=A0 London SW

IT SEEMS THE PROBLEM WITH THIS CHARGER IS FILTERING IN OTHER WORDS OUTPUT WAVE FORM ATTENUATION RECTIFYING IS NOT AN ISSUE OR IT WOULD NOT ADJUST TO THE CHARGE AT ALL

I AM PROTEUS

load.

AND THAT MAKES YOU THE RESIDENT EXPERT ON TROLLS ????

I AM PROTEUSD

Who apparently can't even shout his name correctly.

--

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW To e-mail, change noise into sound.

His teletype obviously needs adjusting.

nt.

And adjust the OC voltage to what?

TMT

And adjust the OC voltage to what?

TMT

A resistor will not change the opencircuit voltage it will only change the current delivered and you will have to decide what is correct for your transformer and your battery.

If this requires some basic training in electricity well so be it.

John G.

Wrong, you just have to add a diode or three to create a voltage drop.

Dave

You just need the right resistor in parallel :-)

Selenium rectifiers have a much higher voltage drop than silicon diodes. When you replace them with modern diodes, you need a resistor in series for most applications, the value of which depends on the design load.

You don't adjust the OC voltage, you adjust the *amperage* into a load, IE, a battery that you wish to charge.

That depends on the battery & how you're charging it, taper charging a lead acid with an upper voltage limit is the normal procedure.

der

ry

rent.

Why the hang-up over the OC voltage? Read what p[eople are saying.

MBQ