# Insulation Resistance Test for EV



## gunnarhs (Apr 24, 2012)

birol said:


> I want to measure the insulation resistance of electric vehicle between power conductors and chassis ground with megger. Are there any IEC, ISO, standarts like minimum resistance value for this test ?


Hi,
I assume you are talking about the minimal resistance between Power train Battery (- High Voltage ground) and chassis (12V ground usually).
The nearest I have seen of regulation is in Australia
http://www.infrastructure.gov.au/ro...COP14_Guidelines_Electric_Drive_01Jan2011.pdf

In Europe are different standards and recommendations, all of the I have seen are just guidelines. They are based on the 
UNECE regulation 100. see more here
http://www.unece.org/fileadmin/DAM/trans/main/wp29/wp29regs/R100r1e.pdf

You will find there for example:
500 Ω/volt for the case that AC and DC Bus are both connected.

If charging circuit is not disconnected to power train then:

For the vehicle inlet intended to be conductively connected to the grounded
external AC power supply and the electrical circuit that is galvanically
connected to the vehicle inlet during charging of the RESS, the isolation
resistance between the high voltage bus and the electrical chassis shall be at least 1 MΩ when the charger coupler is disconnected. ​During the measurement, the traction battery may be disconnected.


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## gunnarhs (Apr 24, 2012)

And here some guides for the test of the resistance.

1) DISCONNECT High power battery and Charger BEFORE measuring the resistance.
2) Be sure that you know all components which are connected between High voltage and low Voltage and their isolation resistance (meaning measure each component extra). usually this includes controller, DC-DC-converter and maybe charger.
3) Still disconnected measure the total resistance between High voltage battery - and chassis (12 v ground) when all components have been added to vehicle.
Note that when two components are connected the total resistance can be less (!) than the original of each component. For example if the controller and the DC-DC-converter also and they are both connected to 12V supply and both have an internal isolation resistance of 2 Mohm (very often the case in DIY-equipment) the total resistance will be 1Mohm (two parallel connected resistances).


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