Re: Unsmoothed car battery charger - is it crap?

I'm the OP. I think my battery charger is over 30 years old!

I took the casing off (rivetted of course) to see the inside:

front =

It sure looks dated!

Eddie

Ooh, I used to have one of those, don't leave it connected for days or it'll boil your battery.

True, but not a big deal. You might want a new strain relief or grommet on the power cord before you cut the cord by not using one where it goes through the case. The quaint power rectifiers are fine until they are not - if they ever go bad, "modern" replacements are fairly simple to get. You probably have a much better ammeter than you'll get in any "modern" charger.

Nothing wrong with old stuff that works.

If you want a smarter charger, you can start here and add smarts, capacitors, whatever makes you happy - timers, pulsers, voltage regulators, the works. The base it's built on hasn't changed much in 70 years.

Selenium rectifiers are still being manufactured (see eg , which refers to a "continuous research and development programme aimed at reliable, lowcost, compact selenium rectifier elements and stacks") but I presume you refer instead to silicon diodes.

...

Well I'm blowed! I'd have never believed that.

They tend to fail after being stored in damp sheds and garages. The awful smell they then emit is always remembered.

Chris

Hahaha... he said "remembered" and he is talking about Selenium.

Ha!

How does the voltage drop compare between the two? Might have a bearing if swopping them.

Not a problem in one of those "brute force" battery chargers, but in a tooobz circuit it can be.

Ed

Selenium rectifiers had considerable drop; I think it was ~~2v per rectifier, but their PIV was so low that a "12 V" battery charger might have 6+ in series....