| Totally discharged battery |
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| Batteries that have not been used for an extended period of time, e.g. in vehicles that have been stored, self-discharge. |
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| A battery is considered to be totally discharged if the no-load voltage has dropped below 11.6 V. Initial battery damage can occur below 12.2 V (if vehicle has been stored for a longer period). |
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| On vehicles without battery monitor control unit -J367- or energy management control unit -J644-, measure no-load voltage → Chapter. |
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| On vehicles with battery monitor control unit -J367- or energy management control unit -J644-, perform battery test using vehicle diagnostic tester → Chapter. |
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| In a totally discharged battery the electrolyte (sulphuric acid/water mixture) is reduced to almost all water, as the sulphuric acid content is heavily reduced. |
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| Totally discharged batteries become sulphated, i.e. the entire battery plate surfaces harden. The electrolyte has a slightly milky appearance (instead of being clear). |
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| If discharged batteries are charged directly after being discharged, the sulphation dissipates. |
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| If this is not done, the plates become even harder and the battery's ability to absorb charge is impaired. This results in reduced power output. |
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| Battery temperature must be at least +10 °C. |
WARNING | Risk of explosion due to a discharged battery with „magic eye“. |
| The battery must NOT be checked or charged if the indicator of the „magic eye“ is colourless or yellow. Do NOT boost start the vehicle. There is a risk of explosion when checking or charging the battery or boost starting the vehicle. The battery must be renewed. |
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Caution | Totally discharged batteries: Danger of freezing. |
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| Totally discharged batteries may freeze even at temperatures only slightly below zero, causing the housing to burst. |
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| Never re-use frozen batteries. |
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| Totally discharged batteries (that are also sulphated) must be charged as follows using a low charging current: |
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| Set charging current to approx. 5 % of battery capacity, i.e. for a 60 Ah battery charging current is approx. 3 A. |
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| Battery voltage must be at least 0.6 V. |
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| Battery chargers -VAS 5095A-, -VAS 5900-, -VAS 5903-, -VAS 5904- and -VAS 5906- detect totally discharged batteries automatically and start the charging process gently at a low charging current. Charging current is adapted automatically to battery charge. |
Caution | Danger of damage to totally discharged batteries. |
| Do NOT attempt to rapid-charge totally discharged batteries. |
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| Charging voltage must not exceed 14.4 V. |
Note | Observe disposal regulations if battery has to be renewed → Anchor. |
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