VS - Electrical Systems From Stop-Start to Hybridization

Evolution of Cranking Capability at Low Temperatures

The figure below shows that @ Low temperature, where the cranking demand is high:

1 For the battery in brand NEW condition the maximum depth of discharge allowed for cranking needs is higher than the usual Depth Of Discharge range. 2 For the battery in some USED condition at low temperatures, the maximum depth of discharge allowed for cranking needs can be lower than the usual Depth Of Discharge range. This demonstrate that cases will exist where, according to electrical load events on the board net, the battery will not be charged enough to secure the next cranking demand.

As already mentioned, the cold crank current (and so the power) is one of the toughest condition that the battery must withstand. The battery type and size must be defined so that in worst case conditions the maximum depth of discharge allowed to crank the engine is higher than the usual battery Depth of Discharge range (green area).

Evolution of cranking capability at low temperatures

Battery power

Usual DoD

1

NEW battery USED battery

2

The red area illustrates a risk

25°C

zone where crank breakdown may occur by lack of power when the battery performances drop.

Aging

Depth of Discharge

In the red area, the maximum Depth of Discharge do not allow to re-crank securely at low temperatures

The red area illustrates a risk zone where crank breakdown may occur by lack of power when the battery performances drop.

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