Re: Unsmoothed car battery charger - is it crap?

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I am.

And I really don't understand why no one is able to provide a simple number of the OC voltage of the charger when it is not hooked up to the battery.

Simple question...if you measure the OC voltage of a battery charger meant for lead acid batteries...what is it?

A number please.

Or better yet how about reporting what your various chargers show as OC DC voltage.

TMT

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How much resistance?

TMT

It depends on so many things that it's impossible to say. For example the off load voltage of just the transformer varies by the design and quality.

Many have a relay on the output operated by the *battery* - with a diode in the feed to its coil - to prevent wrong connection. So show zero volts when not connected. Side effect is they can't be used to try and charge a totally flat battery.

--
*A journey of a thousand sites begins with a single click *

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

What color is my roof?

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You can\'t have a sense of humor, if you have no sense!

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The only simple thing here is you. There are too many variables to give a 'simple' answer.

Even better, quit trolling.

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You can\'t have a sense of humor, if you have no sense!

Let me rephrase it. Read what people are saying, understand it, and then you'll see why no one is answering your question.

There is no one right answer.

Which charger? Which battery?

42

What knowledge do you hope to gain from that, without knowing the characteristics of the various chargers? What if one was 25V, another

16V and yet another 0V, what would that tell you? Are any of them faulty in any way?

MBQ

That's because there isn't one. It's generally raw pulsating DC from a transformer. The battery itself acts as sort of a capacitive filter; when the xformer's instantaneous voltage exceeds the open-circuit voltage of the battery, charging current flows. When it drops below the OCV, the current simply stops flowing and the voltage is whatever the battery is sitting at at the moment.

About 13.8 is a reasonable voltage for a float charge, and they'll go up to as much as 14.4 for an "equalize" charge. But usually they're charged by constant current, so you either need a timer, watch the clock, or buy an expensive charger that figures out all that stuff for you.

I wouldn't try to use a battery charger as, say, a general-purpose high-current power supply without a MONGO LC filter.

Hope This Helps! Rich

Enough to match the forward drop of the selenium stack under normal operating conditions.

Hope This Helps! Rich

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You seem to be the troll here Michael.

TMT

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=A0 London SW

I understand Dave...and I appreciate your response.

I am attempting to have people measure their battery chargers so I have a target voltage to shoot for.

I realize that I can look up what different sources will say an OC voltage is supposed to be but I would like to know what has been done in practice.

TMT

Because you're asking a question to which there is no standard quantifiable answer. You are asking something akin to "how long is a piece of string?" Simply put, the OCV is whatever that particular charger "wants" to put out with no load, and under load will drop to wherever the battery "wants" it to be. The OCV is not regulated and will float to some arbitrary value anywhere from say 5% to 50% greater than the voltage of the battery it is designed to charge, and this will *not* be affected by any resistance you place in series. In fact, you cannot affect the OCV of any voltage source purely by adding resistance unless you add so much resistance that the voltage is dropped measurably by the impedance of the meter you use to measure it. This is just how electricity works, and I'm sorry if you don't understand. Precisely what the voltage is depends on the design of that particular individual charger and may even vary some between two chargers of the same model. It will be affected by line voltage as well. These are simply not precision devices.

You add resistance in order to adjust the amperage to something appropriate for the battery, and the OCV does under load will drop to whatever the battery voltage is.

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DON'T WORRY ABOUT IT I SHALL DEEP PROBE HIM FOR A SOLID AFFIRMITAVE ANSWER [:-]

I AM PROTEUS

But this won't do anything for you. The output voltage will not be affected by adding resistance unless the charger is connected to a load. If there is am amperage rating printed on the face of the charger, you could hook it up to a load such as a couple of automotive headlamp bulbs and adjust the resistance such that the output voltage under a 5-10A load is in the vicinity of 12V, and into a few hundred mA it should be more like 13.8, this isn't rocket science, and the numbers can be very approximate, it really doesn't matter.

If precision is important to you, buy a fancy smart charger that you can "set and forget" and rest easy knowing your batteries will be properly charged even if you leave the charger connected indefinitely.

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I do understand...thanks.

I was asking for an OCV since I considered it a simple request for the group.

TMT

Thanks for the info...it is appreciated.

TMT

What do you mean? African or European battery charger?

Ben Bradley wrote

Africa? Careful - South of the Equator the polarity reverses.

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Roger Hunt

Then its a good thing that the troll is bipolar.

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You can\'t have a sense of humor, if you have no sense!