Today i was working on a machine with 4 6v batteries connected in series.

It was in a building that was very dark and the batteries were covered in dirt and i briefly accidently fitted one of the batteries the wrong way around.

After i corrected the mistake i couldnt get 24v across the four batteries, only 18v, from wherever that battery was out of the voltmeter circuit. Yet the same battery measured 6v on the meter, and load tested ok.

Could the polarity have been reversed on that battery after connecting it the wrong way around?

If so, does charging the 4 batteries in series correct this reverse polarity.


  • 1
    \$\begingroup\$ Can you check the voltage on each battery individually when out of the circuit? Can you measure them when they are all connected? \$\endgroup\$ – Justin Aug 12 '20 at 17:48
  • \$\begingroup\$ Yeah, they all show 6v individually. \$\endgroup\$ – Jo Smit Aug 12 '20 at 17:54
  • \$\begingroup\$ Can you measure them when they are in the circuit? Anyway, it sounds like something is wrong with that battery. Unless the battery was completely empty to start with, you shouldn't have reversed the polarity, but you may have overcharged it. If the battery has a built-in protection circuit, the protection circuit may have tripped. \$\endgroup\$ – user253751 Aug 12 '20 at 17:55
  • \$\begingroup\$ In series: 6V + 6V + 6V - 6V = 12V \$\endgroup\$ – Bort Aug 12 '20 at 18:12
  • \$\begingroup\$ Can you load test all 4 batteries? \$\endgroup\$ – Justin Aug 12 '20 at 18:33

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