DC400 balancer

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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), bu
t 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%.  Ther
e might be enough room to fix one cell internally by paralleling some 18650
s.

However, it's probably 4 to 8 hours of mechanic labor/cost just to umount/o
pen/close/remount the battery pack.  So, i need to verify all the design be
fore 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, wh
ile the rest is around 3.8V. It's kind of strange to consider 3.7V low, whe
n the nominal voltage is 3.75V according to the spec.  So, i am thinking ab
out 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 s
witches 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 b
e able to go to Vegas with the Leaf.

Re: DC400 balancer
On Tuesday, October 20, 2020 at 1:53:31 PM UTC-4, Ed Lee wrote:
Quoted text here. Click to load it
ut 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 shoul
d bring it back to 70%.  If i fix five cells, it should be back to 80%.  Th
ere might be enough room to fix one cell internally by paralleling some 186
50s.
Quoted text here. Click to load it
/open/close/remount the battery pack.  So, i need to verify all the design  
before hand.  
Quoted text here. Click to load it
 (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, w
hen 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.
Quoted text here. Click to load it
m 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.  
Quoted text here. Click to load it
 be able to go to Vegas with the Leaf.


Re: DC400 balancer
On Tuesday, October 20, 2020 at 12:10:08 PM UTC-7, George Herold wrote:
Quoted text here. Click to load it
bout 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 shoul
d bring it back to 70%. If i fix five cells, it should be back to 80%. Ther
e might be enough room to fix one cell internally by paralleling some 18650
s.  
Quoted text here. Click to load it
nt/open/close/remount the battery pack. So, i need to verify all the design
 before hand.  
Quoted text here. Click to load it
ow (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.  
Quoted text here. Click to load it
om both rails, and run the op-amp circuit from 20V. The darington or mosfet
 switches can run directly from 96V. Does it sound reasonable?

Quoted text here. Click to load it

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

Quoted text here. Click to load it

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

Re: DC400 balancer
On Tuesday, October 20, 2020 at 5:18:12 PM UTC-4, Ed Lee wrote:
Quoted text here. Click to load it
 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 sho
uld bring it back to 70%. If i fix five cells, it should be back to 80%. Th
ere might be enough room to fix one cell internally by paralleling some 186
50s.  
Quoted text here. Click to load it
ount/open/close/remount the battery pack. So, i need to verify all the desi
gn before hand.  
Quoted text here. Click to load it
 low (discharging) side. At "low battery warning", #18 to #40 is around 3.7
V, 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 thinkin
g about tapping into 8 sections of 48V, and balancing each 96V segments.  
Quoted text here. Click to load it
from both rails, and run the op-amp circuit from 20V. The darington or mosf
et switches can run directly from 96V. Does it sound reasonable?
Quoted text here. Click to load it
ors 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
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Re: DC400 balancer
On 10/20/2020 1:53 PM, Ed Lee wrote:
Quoted text here. Click to load it

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

Re: DC400 balancer
On Tuesday, October 20, 2020 at 12:15:50 PM UTC-7, bitrex wrote:
Quoted text here. Click to load it
bout 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 shoul
d bring it back to 70%. If i fix five cells, it should be back to 80%. Ther
e might be enough room to fix one cell internally by paralleling some 18650
s.  
Quoted text here. Click to load it
nt/open/close/remount the battery pack. So, i need to verify all the design
 before hand.  
Quoted text here. Click to load it
ow (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.  
Quoted text here. Click to load it
om both rails, and run the op-amp circuit from 20V. The darington or mosfet
 switches can run directly from 96V. Does it sound reasonable?  
Quoted text here. Click to load it
ld be able to go to Vegas with the Leaf.  
Quoted text here. Click to load it
  
Quoted text here. Click to load it

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

Re: DC400 balancer
On Tuesday, October 20, 2020 at 10:53:31 AM UTC-7, Ed Lee wrote:
Quoted text here. Click to load it
ut fixing my Leaf battery. It reports 60% SOH (State of Health/Capacity), b
ut 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.
  
Quoted text here. Click to load it
/open/close/remount the battery pack. So, i need to verify all the design b
efore hand.  
Quoted text here. Click to load it
 (discharging) side. At "low battery warning", #18 to #40 is around 3.7V, w
hile the rest is around 3.8V. It's kind of strange to consider 3.7V low, wh
en the nominal voltage is 3.75V according to the spec. So, i am thinking ab
out tapping into 8 sections of 48V, and balancing each 96V segments.  
Quoted text here. Click to load it
 both rails, and run the op-amp circuit from 20V. The darington or mosfet s
witches can run directly from 96V. Does it sound reasonable?  
Quoted text here. Click to load it
 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 (norma
l playing) of the battery pack.  Except that the wiring diagram (from Nissa
n?) 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 removin
g 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 cont
actor input (battery side) and twelve power lines at the contactor output (
vehicle side).  The vehicle computer will not feed more than 24kwh out, acc
ording 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 (1
0A) 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.

Re: DC400 balancer
On Wednesday, October 21, 2020 at 2:14:28 PM UTC-7, Ed Lee wrote:
Quoted text here. Click to load it
bout 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 shoul
d bring it back to 70%. If i fix five cells, it should be back to 80%. Ther
e might be enough room to fix one cell internally by paralleling some 18650
s.  
Quoted text here. Click to load it
nt/open/close/remount the battery pack. So, i need to verify all the design
 before hand.  
Quoted text here. Click to load it
ow (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.  
Quoted text here. Click to load it
om both rails, and run the op-amp circuit from 20V. The darington or mosfet
 switches can run directly from 96V. Does it sound reasonable?  
Quoted text here. Click to load it
ld be able to go to Vegas with the Leaf.
Quoted text here. Click to load it
mal playing) of the battery pack. Except that the wiring diagram (from Niss
an?) seems to be wrong for the left stack. I think all the cell polarities  
should be reversed.  
Quoted text here. Click to load it

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+...*
.....................................*.................*
......................................*****************

Quoted text here. Click to load it
k 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 removin
g the modules. Connecting outside the stack also provide better cooling.  
Quoted text here. Click to load it
6, 42 for balancing, with 10 ohm, 2W resistors. Four power lines at the con
tactor input (battery side) and twelve power lines at the contactor output  
(vehicle side). The vehicle computer will not feed more than 24kwh out, acc
ording to another video. So, additional batteries must be attached to the v
ehicle side.  
Quoted text here. Click to load it
k 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.  
Quoted text here. Click to load it
te for the job.

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