Lost polarity of battery charger

rock_breaker

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Both of the original battery post clips have been lost on my battery charger so now that I am replacing them I don't know which wire to put the red clamp on, likewise the black one. About a half century ago I read something about putting the leads in a freshly cut potato, when running the charger one of the leads will turn the potato green. I can't remember which one does this so here I am wondering what wire to put the new red clamp on. I would certainly appreciate some help.
Ray
 
Look at the wire and one usually has a ribbing but it is not always standard.

Just plug it in and measure voltage with a voltmeter.

Sent from my SAMSUNG-SGH-I337Z using Tapatalk
 
A DVM will give you a plus or minus voltage, an analog meter will try to go "backwards" if you hook it up wrong. DO NOT let it go backwards but a second or two on the analog meter if that is what you have. It won't hurt the DVM to have it backwards. If you have neither, now is a good time to go to HF and spend like 10 bucks if it's not on their giveaway list and get a DVM. Everyone should have a means of checking voltage and resistance anyway.
 
Harbor Freight 200 miles round trip, do have a multi-meter that reads the same voltage either way. Not sure what DVM stand for but I will check the meter screen again, will have to chase down a magnifying glass to read the fine print.
Thanks for the help and quick response.
Have a good day
Ray
 
DVM is simply Digital Volt Meter. They display a negative sign by the voltage reading to indicate a polarity reversal. If you get a negative sign, that simply means the red lead is on the negative wire, where the black clamp should go. If you get a plus sign, or no sign at all, then the red lead is on the positive wire. This assumes the test leads are correctly inserted in the meter, however. Something to watch for.
 
For an analog (VOM) meter, set the meter to DC(direct current +) and on a voltage scale at least 15 volts. When you connect
up the meter to the charger, the red lead will be Positive(+) and the meter needle will swing to the right and read the battery
charger output voltage indicating the wire connected to the red lead is positive. Reverse the battery charger terminal wires
if the meter swings to the left(this is harmless).

Option 2: Connect up a 12 volt DC motor to a car battery noting the direction of rotation of the motor and also
noting which wire is connected to the positive terminal. Then take the motor wires and hook up the
motor to the charger so that the motor turns in the same direction. The wire on the + of the battery
will be the + on the charger.
 
If you happen to have an LED flash light perhaps you could hack some wires to that. When the polarity is correct you will have light. You can tell positive from negative by taking note which way the batteries went.
 
Your multimeter should have an indication of polarity.

If it doesn't, You can connect one lead to a terminal on your battery and measure the voltage between the other terminal and the other lead. If the voltage is low (around 0 volts), you have it connected correctly. If the voltage is high (around 24 volts) , you have the lead on the wrong terminal. If you don't have a voltmeter, you can do this check with a 12 volt light bulb. Just touch momentarily to avoid burning out the bulb.

Edit: corrected the error in the connection order in the original post. My bad!
 
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