FAQ #125
LV DC-DC Converters and Energy Meter

Last Updated On 11/04/2013 12:25 PM by

mhadngad

Question
EV 4.9.1 states that the energy meter must be wired in such a way that all of the energy “supplying the tractive system” must flow through it. However, if we are using a DC-DC converter to draw LV power from the battery (but not go to the tractive system) can we wire it before the energy meter so the energy used for powering LV electronics does not count towards our efficiency score? Similarly, can we wire the DC-DC converter in such a way that it is always powered by the accumulator thus eliminating the need for an LV battery entirely? This would require putting it before the AIRs but it will be disconnected whenever the LV master power switch is off.
Answer
As the rule says: Only the energy using to propel the car must be recorded by the EnergyMeter, therefore you may wire the DC-DC prior the EnergyMeter. As the DC-DC will always be live with HV, you need to place it within the battery/accumulator container and also fuse it appropriately.
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Rule Numbers
2014:EV4.9.1