Do I need to install a DC-DC charger?

Do I need to install a DC-DC charger?

Smart Alternators

These alternators are controlled by the vehicles ECU. This allows the voltage to be reduced to a lower level when the battery is nearly full, so that engine loads are reduced, less fuel is used and emissions are lowered. This helps manufacturers meet environmental regulations such as Euro 6.
  1. Reduces voltage when vehicle battery charging is not required.
  2. Leisure batteries can be undercharged when using a split charge relay with a smart alternator.

Regenerative Braking

This system takes energy that is normally converted into wasted heat during braking and converts it into electrical energy to re-charge the starter battery. This is made possible by using ECU controlled smart alternators which during braking can boost the alternator voltage output as high as 15V+ to create a burst of charge into the battery. This high voltage puts an increased mechanical load on the engine, resulting in increased engine braking, meaning less of the kinetic energy is converted to wasted heat in the pads and discs. So, the deceleration of the vehicle is putting charge back into the battery, saving fuel that would otherwise be required to re-charge it.
  1. During coasting a smart alternator supplies a boost voltage of 15V+.
  2. Increased engine braking means less wasted heat in brake pads/discs.
  3. The increased voltage from a smart alternator can overcharge some leisure batteries e.g. Gel.

Lithium Batteries

Lithium batteries have a built in BMS (Battery management system) that sets the maximum charging current amongst other things, that the battery is happy to accept. The maximum charge current could be up to 70A and this can cause fuses to blow on the charging circuits that have been designed to charge a traditional lead acid battery.

How can a DC-DC charger help?

During driving, a DC-DC charger provides a fuller, more rapid charge of the Leisure Battery than would be possible with a split charge relay, particularly when a smart alternator is fitted. It will also compensate for any losses in cabling and connectors, which can occur when the leisure battery is located a long way from the vehicle alternator. The life of the leisure battery is increased by providing multi-stage charging, which on some models can be tailored to suit specific battery types such as AGM, Gel, Lithium etc. A DC-DC charger can also help limit the maximum current when charging a flat battery, which can avoid blown fuses, particularly when charging lithium batteries.
  1. Boosts charging if alternator voltage is too low.
  2. Regulates charging if alternator voltage is too high.
  3. Faster, fuller charging of Leisure Battery during driving.
  4. Compensates for losses in cabling & connectors.
  5. Multi-stage charging with selectable battery types.
  6. Limits current to prevent overcharging and blown fuses.

How does a DC-DC charger work?

A DC-DC charger will take whatever output is available from the vehicle alternator/battery and convert this into the most suitable voltage and current to charge the Leisure Battery. If, for example, the incoming voltage from the vehicle battery was only 13V, then the charger could lift this to a 14.5V boost voltage followed by a 13.6V float voltage to ensure the battery becomes safely charged in the shortest possible time.

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