Battery Glossary – Reverse Polarity

Battery Connector PR326EC
A connector designed for reversing polarity

Reverse Polarity – this is when the positive and negative polarity on the battery is reversed. When connecting a reverse polarity battery to a device, the plug that is factory installed with wires reversed on it by the battery manufacturer will keep you from hooking it up incorrectly.

However, if someone orders a replacement battery without providing its unique part # that tells the battery supplier that it is reverse polarity or the fact that it is reverse polarity, it can result in damage to the device when it is installed.  Usually the only thing that denounces what polarity a battery is its unique part # or if you happen to compare the replacement battery to the old battery and notice the black wire and red wire going into the connector plug are entering in different locations.

Reverse Polarity is also referred to as the concept of taking a secondary battery that is completely discharged and connecting a charger to the terminals the wrong way round so that its negative terminal becomes positive and its positive terminal becomes negative.

Some regard this as a myth while others have noted that when it does happen the battery is only of limited use as the current flows are now acting against the ways the the internal plates were designed to operate. As such it is not possible to fully charge the battery and the overall lifespan is dramatically reduced.

The following home video shows two batteries, one of which appears to have reversed polarity.

Correcting reverse polarity in a battery

Where a battery has reverse polarity by error the following can correct it.

  1. Discharge the battery completely – connecting a low amp rated light bulb with no cut out circuitry should do this.
  2. Correctly connect a charger

If the battery refuses to take the charge try a stronger charger for a few seconds (e.g. a 24 volt charger on a 12 volt battery) and then use the correct charger at its lowest settings.

Note in all cases the life span of the battery will have been reduced as deep discharges damage internal components.

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  1. Samuel johnson

    how does a. car battery installed in a car reverse polarity after long time without use.

    1. BatteryGuy

      Generally it would do so if it was completely discharged and then connected to a charger incorrectly

  2. Augustine Mugwagwa

    I am having the same issue here,I did left my car battery on the charger for 12hours,but to my surprise the time I tested the battery voltage with a multimeter,it gave me a nagative reading of -12,4volts. I did put the negative to the positive on the car to start it and it did start . But now my main worry is ,will this battery work like this without causing any damages. It’s doing everything the normal way while positive is now negative.

    1. BatteryGuy

      Theoretically it should work. However I would replace the battery just in case. If your car is under warranty this may also invalidate it.

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