nuggetgalore wrote:Because Kenny mentions a faulty cell, I add here that I manually balanced the cells before putting them back , my scanners (i909 and also Vident) agree max cell is 3.82 V and min cell 3.81V, so not an obviously faulty cell. All other data read on the BMU appears to be normal.
What is this leakage actually? First thought it may be something similar to an earth leakage or residual current detection to stop people getting zapped, I obviously have no idea.
You're not far off. The official fault code description isn't too helpful:http://mmc-manuals.ru/manuals/i-miev/on ... 700ENG.HTM
But what it is is an insulation test failure between the chassis/12v system and the HV system. All EV's have the DC high voltage system essentially "floating" relative to the chassis and 12v system. (In reality there is probably a very high deliberate resistance in the order of megohms to prevent static build up)
All communications between them, such as between the BMU - which is connected to the 12v system and thus chassis referenced, and the CMU boards in the battery pack - which run off the cell module voltages and are thus referenced to the HV system are done via optocouplers, transformers etc... so that there is no galvanic connection between the the low voltage and high voltage system.
One of the safety checks performed when you turn on the car is an insulation test between low voltage and high voltage systems, if this test fails you get P1A44. I was hoping the fault code description would list the minimum allowable resistance/leakage current between the two systems to set the fault unfortunately it is not that specific. My guess is the insulation should be at least a few megohms.
There are some troubleshooting steps listed:http://mmc-manuals.ru/manuals/i-miev/on ... 300ENG.HTM
Anywhere the high voltage and low voltage systems interface is a potential suspect, for example on another thread in here someone found a problem with insulation in the A/C compressor - since the compressor runs from the isolated HV system but has a grounded chassis:viewtopic.php?t=4439
If you've had the battery pack apart to swap cells and the problem is new since then the obvious place to look first would be at the CMU boards that were disturbed, because they connect to the HV system (the entire board runs from the cell module it is connected to) and have optocouplers that connect to the external CAN bus which is 12v/chassis referenced.
A faulty optocoupler or a short on the board between the HV and low voltage sides would trigger this fault. Likewise damaged can bus wiring inside the battery enclosure could cause it - any short between the can bus wiring and one of the battery posts or bus bars would cause it - check for pinched wires.
As to which ECU performs the insulation test I'm not sure but the link above suggests it might be the BMU.