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Re: Unsmoothed car battery charger - is it crap?

Eddie coughed up some electrons that declared:

My car battery is oversized for the car. The battery is a bit old > but usually works fine. The battery is flat (I left the lights > on). > > My fancy new modern charger senses a poor battery and only puts in > very little charge. > > I used to use a really old charger to charge this battery > successfully. I opened up the old charger and saw it was only a > transformer and a big rectifier. That's it. No soothing. > > Is this ok for a car battery or is it way too crude?

Well, it always has been OK - never seen a car charger that was anything but a transformer and some rectifiers - but then I haven't actually bought a new one for 20 years!

The only concern is for the electronics in the car, but generally the battery itself will do the smoothing, which only leaves over-voltage to be a problem, so don't over charge the battery, which would be bad for the battery anyway.

If you're paranoid you could disconnect the +ve and charge the battery in isolation.

Cheers

Tim

Reply to
Tim S
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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 =

formatting link
transformer =
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rectifier =
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It sure looks dated!

Eddie

Reply to
Eddie

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

Reply to
Duncan Wood

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.

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Reply to
Ecnerwal

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.

...

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jiw
Reply to
James Waldby
[...]

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

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Remove prejudice to reply.
Reply to
Chris Whelan

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

Ha!

Reply to
TheQuickBrownFox

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

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    Dave Plowman        dave@davenoise.co.uk           London SW
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Reply to
Dave Plowman (News)

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

Ed

Reply to
ehsjr

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....

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Reply to
David Lesher

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