linear battery chargers vs CTEKs switch mode battery charger

Comparison between a linear battery chargers and CTEKs switch mode battery charger with respect to current and voltage ripple.

A linear battery charger at 9.7 amps gives a voltage ripple with 2V at a mean voltage of 12.5V. This noise can be heard in a radio, for example. The test was conducted in our own lab.

The noise of CTEKs switch mode battery charger is negligible.

The same linear battery charger as above, has a current ripple of 40 amps at a charge current of 9.7 amps.

The current ripple from CTEKs switch mode battery charger is negligible.

40A peak current and below 10A mean current gives a current ripple above 400%. Most manufacturers of VRLA batteries (see battery types) recommend that this value should be below 5%. A traditional battery charger should therefore not be used for these batteries.

other brands vs switch mode battery charger from CTEK

Comparison between a switch mode battery charger of other brands and a switch mode battery charger from CTEK with respect to high frequency current ripple and EMC.

One reason is the heat factor. A battery charger with 400% current ripple can be regarded as a battery charger that charges 4 times the average current for a quarter of the time and with zero current for the remainder of the time. The result is that resistance heat is four times as high using a battery charger of this type compared to a CTEK switch mode battery charger. Inversely, you can charge at double current with a CTEK switch mode battery charger.

A switch mode battery charger of other brand. The high frequency noise emitted from this battery charger is considerable.

The corresponding graph for a CTEK switch mode battery charger shows a negligible noise level.

Certain EMC requirements apply to an electronic product which must be guaranteed by the manufacturer. The tests may be conducted by the manufacturer.

These graphs are of measurements from a switch mode battery charger of other manufacture. None of the lines must cross the yellow line. The grey line shows the background noise in the room. The red line shows the EMC when charging.