Page 3 of 4

Re: Cell Voltage Loss Inspection test (cell-pair test), P33E6

Posted: Sun Jul 21, 2019 11:08 am
by SageBrush
Marktm wrote:Will set up a "test", take data and get back. Fun project for a retired guy! Just hope I don't have to push my leaf for a block to get to the front of my house after I went too far with battery depletion :shock: I was definitely a newbie at that time!

Interesting concept of pushing both "pedals" - it would seem regen and accel at the same time would cancel, or is the CAN system smart enough to only use the disks brakes when accelerating?
^^
Test with the car standing still.

Re: Cell Voltage Loss Inspection test (cell-pair test), P33E6

Posted: Sun Jul 21, 2019 12:02 pm
by Marktm
Got it!

Re: Cell Voltage Loss Inspection test (cell-pair test), P33E6

Posted: Mon Jul 22, 2019 1:20 am
by Dala
Marktm wrote: Quite happy with my 2012 leaf, especially with the "Lizard" replacement battery. However, it does seem that there are two weak cell assemblies - # 75,76. Do you have a recommended procedure that might help rebalance - without "peeling" to the individual cells?

Any success with a replacement business? A company called Fenix Power is working on it in the US - no updates for sometime however :roll:
Only non invasive thing you can do is to keep the car in ON position as much as possible, and charge using the slowest method possible (L1, 110V 6A). That will allow for as much cell balancing as possible.

However, if the cells balance out good at the top SOC, then the situation will not improve. Bottom balancing an EV is inherently much better than top balancing, but the BMS doesn't work that way.

Re: Cell Voltage Loss Inspection test (cell-pair test), P33E6

Posted: Mon Jul 22, 2019 4:17 am
by Marktm
Dala wrote:
Only non invasive thing you can do is to keep the car in ON position as much as possible, and charge using the slowest method possible (L1, 110V 6A). That will allow for as much cell balancing as possible.

However, if the cells balance out good at the top SOC, then the situation will not improve. Bottom balancing an EV is inherently much better than top balancing, but the BMS doesn't work that way.
I will drive to "turtle and beyond" , leaving the Leaf sitting in the on position as much as possible, then charge using my L1 charger (or my OpenEVSE set at 6 amps) - I have the time. Generally, the weak cells #75/76 will be the lowest voltages when at 100% charge, but the differential may only be 20 mv.

Thanks for the advice

Re: Cell Voltage Loss Inspection test (cell-pair test), P33E6

Posted: Mon Jul 22, 2019 4:20 am
by LeftieBiker
This just occurred to me, and it may be nonsense. That said, charging to the EQ stage (all 3 charging lights lit) and then running the heater on Low just might keep the voltage in the EQ stage a bit longer, giving the BMS more time to bring up the weak cells. You might have to turn the heater on and off several times.

Re: Cell Voltage Loss Inspection test (cell-pair test), P33E6

Posted: Mon Jul 22, 2019 2:32 pm
by Marktm
Depleted battery totally today with mix of highway, suburban, sitting with drive on. The final SOC was 2.4% with 4 GIDS. Full power was 80,000 watts right up until turtle. When turtle kicked in, the max was around 7000 watts (LeafSpy battery bar readings). At present L1 charging (for the next 12 hours of so!).

The battery values at shutdown:
Turtle mode capture 7.22.19.jpg
Quite a surprise that the weakest cells are quite different this time - almost a year later than the last "depletion" and that the message is "all cells OK". The only DTCs are the A/C system - it's so hot, it seems 82785 and 6 are thrown regularly.

Re: Cell Voltage Loss Inspection test (cell-pair test), P33E6

Posted: Mon Jul 22, 2019 3:47 pm
by SageBrush
Interesting and good data.
Looks like 3.1 volts -> Turtle

To elicit turtle at a higher SoC due to weak cells you have to stress them, meaning sustained maximum load.

Re: Cell Voltage Loss Inspection test (cell-pair test), P33E6

Posted: Mon Jul 22, 2019 6:06 pm
by Marktm
SageBrush wrote: To elicit turtle at a higher SoC due to weak cells you have to stress them, meaning sustained maximum load.
I actually did the hard accelerations almost until turtle - but of course had to "tool around" close to home right before and during turtle.

Re: Cell Voltage Loss Inspection test (cell-pair test), P33E6

Posted: Mon Jul 22, 2019 6:08 pm
by Marktm
Battery temps went above 100 oF - the highest I've ever seen.

Re: Cell Voltage Loss Inspection test (cell-pair test), P33E6

Posted: Mon Jul 22, 2019 6:14 pm
by SageBrush
Marktm wrote:
SageBrush wrote: To elicit turtle at a higher SoC due to weak cells you have to stress them, meaning sustained maximum load.
I actually did the hard accelerations almost until turtle
Then the weak cells passed the test ... for now

The good news for you is that when those weak cells eventually hobble the pack power, it will be a pack defect warranty rather than a degradation issue