Voltage Guide For 12v Batteries A guide for 12v Car, Commercial, Leisure and Marine batteries |
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A 12 Volt battery contains 6 x 2 volt cells but 12v is the nominal voltage. The actual open circuit voltage of a 100% charged battery is between 12.70v and 12.80v because each cell is approximately 2.13v |
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OCV | ||
12.60v to 12.80v* | ![]() |
Fully charged battery, perfect for fitment to vehicle. |
12.35v to 12.60v* | ![]() |
Acceptable charged battery, acceptable for fitment |
12.00v to 12.35v* | ![]() |
Seriously discharged battery, unacceptable for fitment to vehicle. Action needed - recharge urgently. However, this battery may not fully recover the battery * |
10.60v to 12.00v* | ![]() |
Over used battery, unacceptable for fitment to vehicle. Action needed - recharge urgently However, this may not fully recover the battery * |
10.00v to 10.59v* | ![]() |
Deeply discharged battery or potential faulty cell. Action needed - recharge urgently However, this may not filly recover the battery * |
Less then 10.00v* | ![]() |
Deeply discharged battery, unacceptable for fitment to vehicle Action needed - recharge urgently However, this may not fully recover the battery * |
Notes | ||
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Good Battery. | |
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A flat battery is discharged and NOT a manufacture or warranty battery. Reasons why a battery is 'flat': Over discharged Incorrect charging Malfunction of the charging system Non-approved application Irregular / seasonal use of the vehicle. |
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Probably deeply discharged or potentuly a faulty cell caused by either old age, over use, miss-usage or manufacturing defect. | |
* | At these voltages irreversible sulphation occurs which slowly destroys the active material powering the battery. If discharging has occurred very recently correct charging may partially recover the battery but only if the sulphationlevel is not too severe and even then the level of recover cannot be guaranteed. (The lower the OCV the lower the chances of partial recovery). If the battery will not charge or does not recover after recharing then irreversible internal damage has occurred so the battery will need to be replaced. |