Battery Charger (Which lead is the POS)?

[jw]

I have a battery charger I bought at an auction. It works (lights an auto headlight), but it came without the battery clamps. I bought some clamps, but cant identify which wire is the POS and the NEG. Normally I'd take a multimeter set to DC volts and when the meter shows a + voltage (digital meter), or needle goes up (analog meter), the lead to the +side on the meter would be the POS.

But there's a problem. I cant find my meter, and am tired of looking for it. I need this battery charger now, because my other charger seems to have died. Is there any other way to find which lead is which without a meter?

Yea, I know I could rip the whole charger apart, and usually the POS connects to the internal meter in the charger, but there must be an easier way. Anyone?????

(No, I'm not willing to touch the wires to a battery and hope I get it right or see a shower of sparks, that can damage the charger and/or battery).

Thanks

[micky]

That might only be a couple screws. And the diodes inside might be marked which end is positive also.

Well, if you have a diode, you can put that in the circuit with the headlight and see which way the light lights. If the diode has a |Thanks

[jw]

Come to think of it, I do have some diodes around here, and now that you mention it, I have some LEDS too and resistors. The LED should work well. Now I got to look up which lead is which. I never can remember.

I plan to buy another meter, maybe two more of them. There is no HF around here, but I know Walmart has them for under $10. I'd probably have to pay $10 shipping for a $4 HF meter by mail.

[Stormin Mormon]

You don't have a neighbor who has a meter? Can't take the charger with you to work, and check it there? Take it to TV repair shop, and ask the guy there to check for you? Auto repair garage, and ask them?

I've given it a few minutes thought, and I can't think of another way to determine + and - polarity. Any answer would include a diode, I'm sure.

Might have to wait till your next trip to the city to buy groceries, and buy a VOM there?

Christopher A. Young Learn more about Jesus

.

But there's a problem. I cant find my meter, and am tired of looking for it. I need this battery charger now, because my other charger seems to have died. Is there any other way to find which lead is which without a meter?

Yea, I know I could rip the whole charger apart, and usually the POS connects to the internal meter in the charger, but there must be an easier way. Anyone?????

(No, I'm not willing to touch the wires to a battery and hope I get it right or see a shower of sparks, that can damage the charger and/or battery).

Thanks

[Stormin Mormon]

Ebay, about four bucks, s hippped.

enter the word voltmeter, and then sort by price + shipping, lowest first,

Christopher A. Young Learn more about Jesus

.

I plan to buy another meter, maybe two more of them. There is no HF around here, but I know Walmart has them for under $10. I'd probably have to pay $10 shipping for a $4 HF meter by mail.

[Jules Richardson]

I can't think of any charger I've seen where I couldn't have pulled the case off in the time it must have taken to write that post :-)

An option might be to find something with a 12V DC motor where you know the intended direction of rotation (radiator cooling fan on a modern-ish car, perhaps), and hook it up to that.

cheers

Jules

[Bill Hall]

How close to Texas are you? I could probably drop by on Saturday, with my H.F. meter and we could figure it out in 10-15 minutes! HTH

Sparky

[Stormin Mormon]

15 minutes to determine an A or B polarity output? That's got to be a BIG Texan way to do it?

Less than a minute in NYS. Check one way, then check the other way.

Christopher A. Young Learn more about Jesus

.

How close to Texas are you? I could probably drop by on Saturday, with my H.F. meter and we could figure it out in 10-15 minutes! HTH

Sparky

[mike]

Assuming there's some volts on the battery. Hook one charger wire to ground. Put a light bulb in series with the other wire to the battery. No light, you got it right. If there's light, it's backwards. 12V light will burn out if it lights on 24V. ordinary 120v incandescent should show some glow, but I haven't tried it.

[Joe]

A boy scientist would use the classic water electrolysis experiment and the POS terminal would be the one that has the most gas (Hydrogen) in it...H2), ya know.

Joe

[Percival P. Cassidy]

One of my battery chargers has "figure-8" twin black leads, but the negative has "ribs" running along the side of the insulation, whereas the positive is smooth.

Perce

[JimCo]

A better electrolysis experiment is to use salt water. Chlorine is generated at the positive electrode, and this is easily detectable by its odor. JimCo

[Larry W]

The motor test will only work on permanent magnet motors. If the motor has a would field and wound rotor, it will spin in the same direction regardless of which way you hook it up.

[Stormin Mormon]

You know, it would be interesting if the charger he got has fried diodes, and is delivering AC.

Christopher A. Young Learn more about Jesus

.

A better electrolysis experiment is to use salt water. Chlorine is generated at the positive electrode, and this is easily detectable by its odor. JimCo

[DanG]

Look VERY carefully at the cord. I suspect it is black, flat, kinda divided looking a bit like one of those cheap extension cords your wife uses for lamps, etc. One side of the cord will usually have printing, ridges, or some other identification that is slightly different than the other side. The identified side is the neutral (white in the house, black on 12 volt). The smoother non identified side is the hot (black/red in the house, red or other on 12 volt). The identified neutral is also the larger shaped prong on the male cord cap.

The VOM is still the best way, but I agee with a previous poster that most of the chargers I've opened had as few as one screw and, at most, 4.

[micky]

Good point. I think that it the normal method used.

[HeyBub]

You'll need:

• a large bucket

• two glass quart jars

• water for the bucket

• a couple handfuls of salt

- Put the water and the salt in the bucket.

- tape the leads inside the jars, near the top.

- fill the jars with water and invert in the bucket

- turn on the power

Electrolysis will break down the water into hydrogen and oxygen. Inasmuch as H20 implies twice as many hydrogen atoms as oxygen, one of the jars will fill with a gas twice as fast as the other. That's the hydrogen. It is generated by the negative cathode. Oxygen, conversely, is generated at the positive, anode, terminal.*

Caution: Hydrogen is explosive. Always wear ear, eye, nose, and throat protection. Welder's gloves are appropriate. A lead apron, too.

-------

• I think this is correct. It could be the reverse. Better check first. As some have said, "the facts may be wrong, but the narrative is correct."

[Bernt Berger]

FWIW, I have two Schumachers and an EverStart charger and they all use the ribbed lead for positive and the smooth lead is negative.

[JimCo]

Hide quoted text -

Not quite. If you use salt water, as you said, CHLORINE, not oxygen, will be generated at the POSITIVE anode. HYDROGEN will indeed be generated at the NEGATIVE cathode.. Chlorine is poisonous, and can be detected by its odor. If you collect enough of it, it will be a pale greenish gas. If you use water acidified with a bit of sulfuric acid, then you will indeed get hydrogen at the negative cathode and oxygen at the positive anode. Btw, you really don't need to go so far as to collect any significant amounts of the gases from electrolysis of salt water. By putting your nose close to the electrode that is producing chlorine you should easily detect its distinctive odor. (It smalls exactly like Clorox, which slowly liberates chlorine from the slow decomposition of sodium hypochlorite.)

[HeyBub]

Right. The chlorine comes from the salt (NaCl) used as an electrolyte. In my class we used distilled water and Cobalthorium-g as an electrolyte. No chlorine smell.

But thanks for the correction - it's been a long time and I distinctly remember forgetting the details.