Houston, we have a problem! This message greeted me one day when I turned the car on . Everything turned on except the loud clunk of HV contactor was missing. Considering the car had 8k miles, that was “exciting”..

Once I was done panicking, I hooked up LeafSpy Pro app to the BLE OBDII dongle and scanned for codes.I also checked the 12V battery but that looked fine.

So we have codes:

P31E7 000B	Restart Inhibition	EVC-310
P0AA6 1A08	Hybrid Batt Volt Sys Isolation	EVC-157

P31E7 basically means the HV system detected an error (in this case P0AA6, or HV leak) and disabled car’s restart. Per EVC section of a Gen1 Leaf service manual:

The list of likely culprits made me realize this was not something you fix at home, so I called to have the car towed. I also asked the dealer to arrange for a car loaner. That proved to be a very good idea. It took a few days to diagnose the issue, but almost four weeks to get it back..Meanwhile I was stuck in brand new but slow, loud and miserable ICE Rogue.I called it my tractor..

Timeline:

• April 3 Car throws the error and refuses to start
• April 5 Dealer calls back saying they completed diagnostic and battery cell replacement will be needed
• April 18 New sells and most parts have arrived. Some small parts are still coming
• April 23 Cell re-balancing and pack reassembly stared
• April 25 Car returned. Just a few days short of triggering state’s Lemon Law..

Repair pictures

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Repair invoice

Battery stats: before and after

As soon as I got the car back, I grabbed LeafSpy screenshot of the battery state. The new cells could be identified very easily- their voltage was above the rest. When I checked with the dealer, I was told that’s normal.The cells were balanced using Nissan procedure prior to install and nothing else could be done.It did not seem ok to me, but I figured I’ll keep an eye on it and see if the BMS will eventually bring things closer. That was in April 2019 and 8k miles.

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I’ve logged battery stats monthly since then, and except for an odd cold day in winter, the cells never got close to the old ones.

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Balancing details from EVB manual:

Reading through the EVB-72 section of a Leaf service manual, the balancing procedure is as follows. Find a max cell voltage in the pack, double it and bring the new module (two cells in series) to that value +/-10mV either by charging or by first discharging to 5V and then charging. End result should be within 33mV from highest cell. These are 2014 specs, so they may have changed with newer chemistry. It does seem to match the description on the invoice “Replace both cells as a pack and balanced to 2 times max cell voltage”

Summary:

• It appears my car was affected by an early cell failure- shorted to case.
• Reports of similar issues are starting to pop in on forums, usually with sub 10k miles and on 2018-2019 models.
• Balancing may or may not be done correctly during replacement.
• My pack’s imbalance is likely limiting the range since new cells hit top voltage limit before the rest. In fact I am yet to see GOM go back to 150 miles on full charge, like it used to.(see first picture). So far I am mostly stuck at 130 miles or so. If a DCFC ever appears in the area, I might try a few cycles to see if that brings the cells closer during rapid charge.
• If you car throws this error:
  • Make sure you get a loaner car
  • Get the codes and give them to dealer. Might save a bit of time if they know what they are dealing with in advance
  • Get ready to wait. Cells alone take weeks to ship ground. It took almost 4 weeks to get car back

Resources

My Nissan Leaf forum thread