3 cells sagging, tortoise at 6 bars

[vh2q]

Tortoise is coming on with 6 bars left. 3 cells are sagging down to 3.5v under normal driving. If I shut her down for a few minutes, tortoise goes away for a while. At rest at 5 bars, all cells are within .05v or so. Car will charge to 16 bars and again, all cells are level within .05v. One cell is consistently a tad stronger than the others.

History: I replaced one cell that lagged the rest quite significantly, preventing the pack from charging more than 4 bars. That cell was a little higher than the rest when I put it in, and is still a tad higher than the rest at full charge, after maybe 12 cycles.

Do I now need to drop the pack again to replace the 3 sagging cells?

 

[MickeyS70]

Do I now need to drop the pack again to replace the 3 sagging cells?

Hi there
Most likely and from experience of other drivers be prepared to do this on a regular basis from now on.
It looks like your traction battery has significantly degraded; how old is your pack, what is the mileage of the car, what the climate you’re driving and do you know the current capacity or SOH?

Mickey

 

[vh2q]

Car is a 2012 and has done only about 26k miles. Climate is warm but hobdrive indicates cell Temps in the high 80s low 90s. I am getting 60 mile range about 4 miles per bar, except the last 5 bars I have to crawl due to the tortoise being triggered by the 3 saggers, or stop periodically. Also, I only get 1.6 miles on the first bar as the replaced cell gets to full volts first and the charger shuts down at that point.

 

[MickeyS70]

Also, I only get 1.6 miles on the first bar as the replaced cell gets to full volts first and the charger shuts down at that point.

Mine does something similar, one cell has a constant high offset (40mV) but I put this down to a CMU problem, however from your description is seems that the replacement cell has a lower capacity and is therefore charged quicker?

At 100% charge what is the voltage difference between the two highest cells? Did you try cell balancing in HobDrive yet?

 

[vh2q]

New cell was higher than the pack when I put it in. It's gradually coming into line. Hobdrive cell Balancing function is inop as best I can tell, get mmessage I have to purchase the full version but I already did that.

After overnight full charge, weakest cell is 4.070, most cells at 4.075, the new cell is at 4.095.. capacity is 36Ah, 75%.

 

[MickeyS70]

Ok, that makes sense. Once your pack is balanced, your sagging cells should get some additional charge which can delay your tortoise problem but don’t expect great improvements, they need to be replaced (but most likely will only give you short term relief, I’m afraid)

What CMU are these problem cells and the one you already replaced on? Just a single one or randomly spread out?

 

[vh2q]

They are spead out. 13 and 38 are the worst saggers. 41 was replaced, it was so far behind the rest of the pack the charger would quit at 4 bars.

I got hobdrive cell Balancing to engage but after a few mins it switches off
My Bluetooth connection cuts in and out.

I would replace the entire pack if I could be sure the replacement was going to last longer than this pack. 25k miles is poor.

 

[MickeyS70]

I would replace the entire pack if I could be sure the replacement was going to last longer than this pack. 25k miles is poor.

25k is certainly below average but unless you know it’s compete history one can only guess as to why..

A 2012 model most likely has a LEV50 pack as there is a good chance it was built before the cells were replaced with improved LEV50N.

There are very few decent original packs still available, a change to LEV50N will require a BMU upgrade…

 

[vh2q]

I am happy to say that after a few more charging cycles and using hobdrive to level the pack, we now have a 98% soc and were able to easily make a 50 mile trip yesterday without a visit from the turtle limiter, albeit on level ground at moderate speeds. We had 7 bars left. So I am thinking my bars are out of whack ie overstating reality. However hobdrive also showed 48% remaining charge after the trip. I will try running it down to empty, that is supposed to recalibrate the bars somehow.

 

[MickeyS70]

I will try running it down to empty, that is supposed to recalibrate the bars somehow.

You’re on the right track, the BMU will re-calculate the battery capacity if

- you first discharge the battery below approximately 339V
- then level 1 charge all the way to 100%
- and leave it sitting idly for a while afterwards

The BMU will only change the value by max +/-1Ah. If you suspected bigger corrections are needed use HobDrive’s battery calibration function.

 

[MickeyS70]

I will try running it down to empty, that is supposed to recalibrate the bars somehow.

You’re on the right track, the BMU will re-calculate the battery capacity if

- you first discharge the battery below approximately 339V
- then level 1 charge all the way to 100%
- and leave it sitting idly for a while afterwards

The BMU will only change the value by max +/-1Ah each time round. If you suspected bigger corrections are needed use HobDrive’s battery calibration function.

 

[Lithim]

Does anyone know the vehicle production date or VIN number as to when the batteries where changed from LEV50 to LEV50N?

Turtle coming on frequently with cooler weather. Max range high 30's, low 40's.

Silver 2012 with QC
Charge at home with original OEM level 1 EVSE
Original owner
61729 miles
Houston

 

[vh2q]

Seems I declared victory too soon. Car sat for a couple months on half charge. Then running local short errands I took it down to 2 bars and did a 110 charge to full bars. Made a longer run 23 miles, getting good range circa 4 miles per bar. However on the way back, at about half charge turtle started coming on. Had to stop periodically and limp home the last 15 miles with 5 bars remaining. Cell profile immediately after getting home was a bit ragged with lowest cell at 3.55v highest about 3.7, this being the replaced cell. Was not able to get a profile while in motion.

 

[MickeyS70]

Unfortunately that is the experience of most owners replacing single cells, it becomes a game of ‘whack a mole’…

 

[vh2q]

Drove today with hobdrive active on cell voltage screen. Three cells sagging badly circa 3v when gauge is on half, three more marginal. The one cell I replaced remains head and shoulders above the rest. I think it may be the later version even though it came out of a 2012. It is a different color and slightly different height. Had to crawl home. Stopping even for a few mins allows weak cells to recover. Their static voltage is in line with the rest of the pack once rested. They just can't put out much amperage when they get to half charge, without sagging below 3v.

Needless to say, I am looking for some good cells. A 6 pack would work.

 

[MickeyS70]

Drove today with hobdrive active on cell voltage screen. Three cells sagging badly circa 3v when gauge is on half, three more marginal. The one cell I replaced remains head and shoulders above the rest. I think it may be the later version even though it came out of a 2012. It is a different color and slightly different height. Had to crawl home. Stopping even for a few mins allows weak cells to recover. Their static voltage is in line with the rest of the pack once rested. They just can't put out much amperage when they get to half charge, without sagging below 3v.

Needless to say, I am looking for some good cells. A 6 pack would work.

LEV50’s came in different colours and heights, your ‘new’ 2012 cell being way above the rest just means your pack isn’t in great shape I’m afraid.

 

[suziauto]

needs a new pack... not sure where you are .. We have installers in quite a few places..www.ozelectricvehicles.com.au

 

[vh2q]

Abaco unfortunately. That's an island in the Atlantic.