DC400 balancer...

[Ed Lee]

For couple of months ( or years), i\'ve been talking (mostly thinking) about fixing my Leaf battery. It reports 60% SOH (State of Health/Capacity), but it\'s based on the lowest cell (#40 of 96). If i fix one cell, it should bring it back to 70%. If i fix five cells, it should be back to 80%. There might be enough room to fix one cell internally by paralleling some 18650s.

However, it\'s probably 4 to 8 hours of mechanic labor/cost just to umount/open/close/remount the battery pack. So, i need to verify all the design before hand.

The Leaf BMS manage well on the high (charging) side, but poor on the low (discharging) side. At \"low battery warning\", #18 to #40 is around 3.7V, while the rest is around 3.8V. It\'s kind of strange to consider 3.7V low, when the nominal voltage is 3.75V according to the spec. So, i am thinking about tapping into 8 sections of 48V, and balancing each 96V segments.

It\'s difficult to find 96V op-amp. I can probably shunt regulate 40V from both rails, and run the op-amp circuit from 20V. The darington or mosfet switches can run directly from 96V. Does it sound reasonable?

With this fix and the three free DCFC coming on I-15 rest stops, i should be able to go to Vegas with the Leaf.

 

[George Herold]

On Tuesday, October 20, 2020 at 1:53:31 PM UTC-4, Ed Lee wrote:

For couple of months ( or years), i\'ve been talking (mostly thinking) about fixing my Leaf battery. It reports 60% SOH (State of Health/Capacity), but it\'s based on the lowest cell (#40 of 96). If i fix one cell, it should bring it back to 70%. If i fix five cells, it should be back to 80%. There might be enough room to fix one cell internally by paralleling some 18650s.

However, it\'s probably 4 to 8 hours of mechanic labor/cost just to umount/open/close/remount the battery pack. So, i need to verify all the design before hand.

The Leaf BMS manage well on the high (charging) side, but poor on the low (discharging) side. At \"low battery warning\", #18 to #40 is around 3.7V, while the rest is around 3.8V. It\'s kind of strange to consider 3.7V low, when the nominal voltage is 3.75V according to the spec. So, i am thinking about tapping into 8 sections of 48V, and balancing each 96V segments.

It\'s difficult to find 96V op-amp. I can probably shunt regulate 40V from both rails, and run the op-amp circuit from 20V. The darington or mosfet switches can run directly from 96V. Does it sound reasonable?

Not sure about battery balancing, but the LTC6090 is a nice HV opamp
if you can afford the ~$10 price.
George H.

With this fix and the three free DCFC coming on I-15 rest stops, i should be able to go to Vegas with the Leaf.

 

[bitrex]

On 10/20/2020 1:53 PM, Ed Lee wrote:

For couple of months ( or years), i\'ve been talking (mostly thinking) about fixing my Leaf battery. It reports 60% SOH (State of Health/Capacity), but it\'s based on the lowest cell (#40 of 96). If i fix one cell, it should bring it back to 70%. If i fix five cells, it should be back to 80%. There might be enough room to fix one cell internally by paralleling some 18650s.

However, it\'s probably 4 to 8 hours of mechanic labor/cost just to umount/open/close/remount the battery pack. So, i need to verify all the design before hand.

The Leaf BMS manage well on the high (charging) side, but poor on the low (discharging) side. At \"low battery warning\", #18 to #40 is around 3.7V, while the rest is around 3.8V. It\'s kind of strange to consider 3.7V low, when the nominal voltage is 3.75V according to the spec. So, i am thinking about tapping into 8 sections of 48V, and balancing each 96V segments.

It\'s difficult to find 96V op-amp. I can probably shunt regulate 40V from both rails, and run the op-amp circuit from 20V. The darington or mosfet switches can run directly from 96V. Does it sound reasonable?

With this fix and the three free DCFC coming on I-15 rest stops, i should be able to go to Vegas with the Leaf.

I mean, nothing about any of this sounds \"reasonable\" from a variety of
perspectives but I suppose that\'s not what you\'re asking.

 

[Ed Lee]

On Tuesday, October 20, 2020 at 12:15:50 PM UTC-7, bitrex wrote:

On 10/20/2020 1:53 PM, Ed Lee wrote:
For couple of months ( or years), i\'ve been talking (mostly thinking) about fixing my Leaf battery. It reports 60% SOH (State of Health/Capacity), but it\'s based on the lowest cell (#40 of 96). If i fix one cell, it should bring it back to 70%. If i fix five cells, it should be back to 80%. There might be enough room to fix one cell internally by paralleling some 18650s.

However, it\'s probably 4 to 8 hours of mechanic labor/cost just to umount/open/close/remount the battery pack. So, i need to verify all the design before hand.

The Leaf BMS manage well on the high (charging) side, but poor on the low (discharging) side. At \"low battery warning\", #18 to #40 is around 3.7V, while the rest is around 3.8V. It\'s kind of strange to consider 3.7V low, when the nominal voltage is 3.75V according to the spec. So, i am thinking about tapping into 8 sections of 48V, and balancing each 96V segments.

It\'s difficult to find 96V op-amp. I can probably shunt regulate 40V from both rails, and run the op-amp circuit from 20V. The darington or mosfet switches can run directly from 96V. Does it sound reasonable?

With this fix and the three free DCFC coming on I-15 rest stops, i should be able to go to Vegas with the Leaf.

I mean, nothing about any of this sounds \"reasonable\" from a variety of
perspectives but I suppose that\'s not what you\'re asking.

Why not? around 10% of the cells are at 70% and 90% at 80%+. I just need to even it out close to 80%.

 

[Ed Lee]

On Tuesday, October 20, 2020 at 12:10:08 PM UTC-7, George Herold wrote:

On Tuesday, October 20, 2020 at 1:53:31 PM UTC-4, Ed Lee wrote:
For couple of months ( or years), i\'ve been talking (mostly thinking) about fixing my Leaf battery. It reports 60% SOH (State of Health/Capacity), but it\'s based on the lowest cell (#40 of 96). If i fix one cell, it should bring it back to 70%. If i fix five cells, it should be back to 80%. There might be enough room to fix one cell internally by paralleling some 18650s.

However, it\'s probably 4 to 8 hours of mechanic labor/cost just to umount/open/close/remount the battery pack. So, i need to verify all the design before hand.

The Leaf BMS manage well on the high (charging) side, but poor on the low (discharging) side. At \"low battery warning\", #18 to #40 is around 3.7V, while the rest is around 3.8V. It\'s kind of strange to consider 3.7V low, when the nominal voltage is 3.75V according to the spec. So, i am thinking about tapping into 8 sections of 48V, and balancing each 96V segments.

It\'s difficult to find 96V op-amp. I can probably shunt regulate 40V from both rails, and run the op-amp circuit from 20V. The darington or mosfet switches can run directly from 96V. Does it sound reasonable?

Not sure about battery balancing, but the LTC6090 is a nice HV opamp

It\'s possible, but 3mA at 96V is a bit high. I can run the shunt regulators and op-amp at 1mA.

> if you can afford the ~$10 price.

Yes, it\'s pricy, but well worth it if it works.

 

[George Herold]

On Tuesday, October 20, 2020 at 5:18:12 PM UTC-4, Ed Lee wrote:

On Tuesday, October 20, 2020 at 12:10:08 PM UTC-7, George Herold wrote:
On Tuesday, October 20, 2020 at 1:53:31 PM UTC-4, Ed Lee wrote:
For couple of months ( or years), i\'ve been talking (mostly thinking) about fixing my Leaf battery. It reports 60% SOH (State of Health/Capacity), but it\'s based on the lowest cell (#40 of 96). If i fix one cell, it should bring it back to 70%. If i fix five cells, it should be back to 80%. There might be enough room to fix one cell internally by paralleling some 18650s.

However, it\'s probably 4 to 8 hours of mechanic labor/cost just to umount/open/close/remount the battery pack. So, i need to verify all the design before hand.

The Leaf BMS manage well on the high (charging) side, but poor on the low (discharging) side. At \"low battery warning\", #18 to #40 is around 3.7V, while the rest is around 3.8V. It\'s kind of strange to consider 3.7V low, when the nominal voltage is 3.75V according to the spec. So, i am thinking about tapping into 8 sections of 48V, and balancing each 96V segments.

It\'s difficult to find 96V op-amp. I can probably shunt regulate 40V from both rails, and run the op-amp circuit from 20V. The darington or mosfet switches can run directly from 96V. Does it sound reasonable?

Not sure about battery balancing, but the LTC6090 is a nice HV opamp

It\'s possible, but 3mA at 96V is a bit high. I can run the shunt regulators and op-amp at 1mA.

There is a nice power pad on the IC... I\'m guessing it can dissipate
~300 mW with a decent size copper pad. (But you\'ll have to read the spec
sheet.)
GH

if you can afford the ~$10 price.

Yes, it\'s pricy, but well worth it if it works.

 

[Ed Lee]

On Tuesday, October 20, 2020 at 10:53:31 AM UTC-7, Ed Lee wrote:

For couple of months ( or years), i\'ve been talking (mostly thinking) about fixing my Leaf battery. It reports 60% SOH (State of Health/Capacity), but it\'s based on the lowest cell (#40 of 96). If i fix one cell, it should bring it back to 70%. If i fix five cells, it should be back to 80%. There might be enough room to fix one cell internally by paralleling some 18650s.

However, it\'s probably 4 to 8 hours of mechanic labor/cost just to umount/open/close/remount the battery pack. So, i need to verify all the design before hand.

The Leaf BMS manage well on the high (charging) side, but poor on the low (discharging) side. At \"low battery warning\", #18 to #40 is around 3.7V, while the rest is around 3.8V. It\'s kind of strange to consider 3.7V low, when the nominal voltage is 3.75V according to the spec. So, i am thinking about tapping into 8 sections of 48V, and balancing each 96V segments.

It\'s difficult to find 96V op-amp. I can probably shunt regulate 40V from both rails, and run the op-amp circuit from 20V. The darington or mosfet switches can run directly from 96V. Does it sound reasonable?

With this fix and the three free DCFC coming on I-15 rest stops, i should be able to go to Vegas with the Leaf.

https://www.youtube.com/watch?v=vYQJatWpBXY (at 18:44)

This guy did a tear-down (running the video backward) and reassembly (normal playing) of the battery pack. Except that the wiring diagram (from Nissan?) seems to be wrong for the left stack. I think all the cell polarities should be reversed.

My wiring diagram (copy to fixed pitch font viewer) is:

*****************
* *
24- 24+ * 36+ 36- * 35+ 35- *
* * * *
23+ 23- ******************* 33- 33+ * 34- 34+ *
* * * * *
22- 22+ 26+ 26- * 25+ 25- 32+ 32- * 31+ 31- *
* * * *
21+ 21- 27- 27+ * 28- 28+ * 29- 29+ * 30- 30+ *
* *
....
* *
4- 4+ 46+ 46- * 45+ 45- * 44+ 44- * 43+ 43- *
* * * *
3+ 3- 47- 47+ * 48- 48+ 41- 41+ * 42- 42+ *
* * *
2* 2- 40+ 40- * 39+ 39- *
* * *
1+ 1- 37- 37+ * 38- 38+ *
* *
*****************

In my case, most of the weak cells are in the back stack. So, lots of work to take them out for replacement. But it might be possible to just attach additional 18650s to the cell terminals (M6 and M4 screws) without removing the modules. Connecting outside the stack also provide better cooling.

Work order:

Attach 4 sets of pre-wired 18650 (2.2Ahr) modules.
60% #40 module 20 right (8x18650)
70% #31 module 16 left (6x18650)
72% #18 module 9 right (5x18650)
75% #68 module 34 right (4x18650)

Attach 7 wires at positive (red) terminals of module 6, 12, 18, 24, 30, 36, 42 for balancing, with 10 ohm, 2W resistors. Four power lines at the contactor input (battery side) and twelve power lines at the contactor output (vehicle side). The vehicle computer will not feed more than 24kwh out, according to another video. So, additional batteries must be attached to the vehicle side.
l
Drill two holes in the upper casing cover (and vehicle side under the back seats) and install two SP21 (12 pins, 5A) base connectors. Double wires (10A) for the internal power lines and 6x wires (30A) for the external power lines.

I\'ll get the parts (including the high voltage glove) ready and get a quote for the job.

 

[Ed Lee]

On Wednesday, October 21, 2020 at 2:14:28 PM UTC-7, Ed Lee wrote:

On Tuesday, October 20, 2020 at 10:53:31 AM UTC-7, Ed Lee wrote:
For couple of months ( or years), i\'ve been talking (mostly thinking) about fixing my Leaf battery. It reports 60% SOH (State of Health/Capacity), but it\'s based on the lowest cell (#40 of 96). If i fix one cell, it should bring it back to 70%. If i fix five cells, it should be back to 80%. There might be enough room to fix one cell internally by paralleling some 18650s.

However, it\'s probably 4 to 8 hours of mechanic labor/cost just to umount/open/close/remount the battery pack. So, i need to verify all the design before hand.

The Leaf BMS manage well on the high (charging) side, but poor on the low (discharging) side. At \"low battery warning\", #18 to #40 is around 3.7V, while the rest is around 3.8V. It\'s kind of strange to consider 3.7V low, when the nominal voltage is 3.75V according to the spec. So, i am thinking about tapping into 8 sections of 48V, and balancing each 96V segments.

It\'s difficult to find 96V op-amp. I can probably shunt regulate 40V from both rails, and run the op-amp circuit from 20V. The darington or mosfet switches can run directly from 96V. Does it sound reasonable?

With this fix and the three free DCFC coming on I-15 rest stops, i should be able to go to Vegas with the Leaf.
https://www.youtube.com/watch?v=vYQJatWpBXY (at 18:44)

This guy did a tear-down (running the video backward) and reassembly (normal playing) of the battery pack. Except that the wiring diagram (from Nissan?) seems to be wrong for the left stack. I think all the cell polarities should be reversed.

My wiring diagram (copy to fixed pitch font viewer) is:

*****************
* *
24- 24+ * 36+ 36- * 35+ 35- *
* * * *
23+ 23- ******************* 33- 33+ * 34- 34+ *
* * * * *
22- 22+ 26+ 26- * 25+ 25- 32+ 32- * 31+ 31- *
* * * *
21+ 21- 27- 27+ * 28- 28+ * 29- 29+ * 30- 30+ *
* *
...
* *
4- 4+ 46+ 46- * 45+ 45- * 44+ 44- * 43+ 43- *
* * * *
3+ 3- 47- 47+ * 48- 48+ 41- 41+ * 42- 42+ *
* * *
2* 2- 40+ 40- * 39+ 39- *
* * *
1+ 1- 37- 37+ * 38- 38+ *
* *
*****************

Show better with \'.\' instead of spaces:

.......................................*****************
......................................*.................*
24-..24+.*..........................36+.36-.*.35+.35-...*.
..*........*........................................*....*
23+..23-...*******************......33-.33+.*.34-.34+...*
.......*........................*.....*...*..............*
22-..22+........26+.26-.*.25+.25-...32+.32-.*.31+.31-...*
..*...............*.................................*....*
21+..21-........27-.27+.*.28-.28+.*.29-.29+.*.30-.30+...*
.......*.................................................*
....
.......*.................................................*
..4-...4+........46+.46-.*.45+.45-.*.44+.44-.*.43+.43-...*
...*..............*................................*.....*
..3+...3-........47-.47+.*.48-.48+...41-.41+.*.42-.42+...*
.......*..............................*..................*
..2*...2-............................40+.40-.*.39+.39-...*
..*.................................................*....*
..1+...1-............................37-.37+.*.38-.38+...*
......................................*.................*
.......................................*****************

In my case, most of the weak cells are in the back stack. So, lots of work to take them out for replacement. But it might be possible to just attach additional 18650s to the cell terminals (M6 and M4 screws) without removing the modules. Connecting outside the stack also provide better cooling.

Work order:

Attach 4 sets of pre-wired 18650 (2.2Ahr) modules.
60% #40 module 20 right (8x18650)
70% #31 module 16 left (6x18650)
72% #18 module 9 right (5x18650)
75% #68 module 34 right (4x18650)

Attach 7 wires at positive (red) terminals of module 6, 12, 18, 24, 30, 36, 42 for balancing, with 10 ohm, 2W resistors. Four power lines at the contactor input (battery side) and twelve power lines at the contactor output (vehicle side). The vehicle computer will not feed more than 24kwh out, according to another video. So, additional batteries must be attached to the vehicle side.
l
Drill two holes in the upper casing cover (and vehicle side under the back seats) and install two SP21 (12 pins, 5A) base connectors. Double wires (10A) for the internal power lines and 6x wires (30A) for the external power lines.

I\'ll get the parts (including the high voltage glove) ready and get a quote for the job.