Voltage between HV and Ground [SOLVED]

[Alibro]

Hi guys
During testing I discovered I have approx 70V to 76V between the live terminal of the HV battery connection in my HV junction box and chassis ground.

If I connect between the HV Pos and chassis ground using a 180R 1/4W resistor (so it would pop if there was a real short) The voltage goes to 0V with no current I can measure. When I disconnect the resistor the voltage immediately jumps to 70V then creeps up slowly

I see the same voltage at all times whether the rear battery pack is disconnected or not
It also shows whether all 12V connections are connected or not.

In my setup I have 40 cells in the front of the car so approx 160V and 56 in the rear with the pack positive going from the rear to the front battery box and the pack neg from the rear going directly to the HV junction box.

Any suggestions what is causing it, should I be concerned and could it mess up the VCU coms to the inverter?
Could it be capacitance?

Any help gratefully received thanks

[johu]

That is normal. A 100k or higher resistor should make it collapse, otherwise it's serious

[arber333]

....
Any suggestions what is causing it, should I be concerned and could it mess up the VCU coms to the inverter?
Could it be capacitance?

Any help gratefully received thanks

Do you have any nonautomotive heater that uses liquid for heat transfer? You could have a fault in the heating element which would come in contact with the liquid and HV.

Also i noticed some low voltage mosfet based inverters dont have isolated base cooling plate from the gnd. You can notice that by measuring the negative line to base plate and you can measure resistance in kohms.

[Alibro]

That is normal. A 100k or higher resistor should make it collapse, otherwise it's serious

Thanks mate
I'll try a 100k resistor to confirm but there was no current or spark with a 180R resistor so hopefully it is OK.

[Alibro]

Do you have any nonautomotive heater that uses liquid for heat transfer? You could have a fault in the heating element which would come in contact with the liquid and HV.

Also i noticed some low voltage mosfet based inverters dont have isolated base cooling plate from the gnd. You can notice that by measuring the negative line to base plate and you can measure resistance in kohms.

I have a Nissan Leaf heater but it wasn't connected so shouldn't be the problem. Johu seems to think it's normal.

[RetroZero]

A potential leak through a HV relay/ contactor? Anything higher than 60vdc is considered high voltage in automotive world. Hope you find the source,even if it's ok, always good to watch out for potential short circuits.

[Alibro]

A potential leak through a HV relay/ contactor? Anything higher than 60vdc is considered high voltage in automotive world. Hope you find the source,even if it's ok, always good to watch out for potential short circuits.

I don't think it can be a leak through a contactor as it is only showing on the unswitched side of the contactor. I didn't check the precharge relay so maybe.
As already mentioned Johu thinks it's normal so I'll move on and try to figure out why I'm struggling to get the VCU to behave. It gives me a ground on outputs 1 and 2 occasionally but only when it feels like it.