Charging Totally Discharged Batteries

Charging Totally Discharged Batteries

Batteries that have not been used for long periods of time begin to self discharge (e.g. vehicles in storage). Under these conditions, the battery begins to sulfate and the surface area of the battery plates hardens. A battery is considered to be totally discharged if the no load voltage is below 11.6 volts. No load voltage, checking.

On totally discharged batteries, the electrolyte (sulfuric acid/water mixture) is almost all water. When these batteries are exposed to freezing temperatures, permanent damage to the battery plates (and housing) results.

If a totally discharged battery is charged quickly ("quick charged" or "boost charged"), only a surface charge is accepted (if at all). The battery may even test OK immediately after charging. However, in this case the sulfating process continues inside the battery. Once a battery begins to sulfate, it's ability to further accept a routine charge (from the Generator) and provide adequate load and reserve performance will diminish until the battery malfunctions.

Totally discharged batteries must only be slow charged and re-tested.
- Apply a maximum charge current that is no more than 10% of battery capacity, e.g.: for a 60 Ah battery, max. charge current = 6 amps.
- Charge a totally discharged battery for a minimum of 24 hours.

CAUTION: Never "quick charge" a totally discharged battery. Effective charging will not take place, despite what appears to be a sufficient voltage applied. Batteries loaded in this manner may be incorrectly evaluated as OK and battery damage may result.