Lothsahn
Posts: 497
Joined: Thu Apr 05, 2018 4:35 pm
Delivery Date: 04 Jan 2018
Leaf Number: 007797

Re: Leaf range after battery module replacement

Fri Oct 11, 2019 9:51 am

nlspace wrote:
Fri Oct 11, 2019 9:36 am
You have an incorrect assumption--that the BMS balancer pulls current from one cell to charge another.

The bleed resistors (430 ohms) on the LBC board can only burn off excess energy of a higher cell to bring it down to the level of the lower cells. The ASIC chips have internal transistors that provide the switch path for the balancing control of each individual cell in the 4-cell groups that each chip monitors and controls.

There is no shuttling of charge around the board from high cells to low cells.
Yes, if that's how it works, I misunderstood for sure. If it's bleeing the charge off, the best case scenario is a high level SOC (higher voltage = higher bleed at the same resistance) for a long period of time.

If you want to try to balance it with the BMS, charge the car to 80%, leave it running in the garage at minimum power draw (with no heat/AC, etc) for hours until it gets to about 40%, charge via L1, and repeat until balanced. May take many cycles.

Again, I recommend that gary take the car back to the dealer and have it serviced properly.



Edit: Some quick math: 430 ohms at 3.7v = 0.032W power draw. Given a rated capacity of 56 AH, and assuming that the battery is 30% overcharged beyond the other cells (based on the range drop), that's a total of 16.8 extra AH in the battery. At a voltage of 3.7V, that's 62.16 WH in the cell. At .032W balancing draw, the car should fix itself after 1942 hours of operation--80 days nonstop.

Feel free to correct my math. If it's correct, I wouldn't want to rely on the BMS to balance those cells. Take the car to the dealer and have them fix it correctly. :)
2011 Silver SV, purchased 2018, lives in Missouri (previously in CA)
LeafSpy Pro + BAFX Products OBDII dongle
Battery swap 2019/04/24 (87% SOH, 12 bar)

DaveinOlyWA
Posts: 14149
Joined: Sat Apr 24, 2010 7:43 pm
Delivery Date: 16 Feb 2018
Leaf Number: 314199
Location: Olympia, WA
Contact: Website

Re: Leaf range after battery module replacement

Fri Oct 11, 2019 11:37 am

Looks like a piss poor job of matching cells to the existing pack. Give it time, they will eventually self balance. Will likely take at least a month though.
2011 SL; 44,598 miles. 2013 S; 44,840 miles.2016 S30 deceased. 29,413 miles. 2018 S40; 15,000 miles, 478 GIDs, 37.0 kwh 109.81 Ahr , SOH 94.61, Hx 120.15
My Blog; http://daveinolywa.blogspot.com" onclick="window.open(this.href);return false;

LeftieBiker
Moderator
Posts: 13228
Joined: Wed May 22, 2013 3:17 am
Delivery Date: 30 Apr 2018
Location: Upstate New York, US

Re: Leaf range after battery module replacement

Fri Oct 11, 2019 12:46 pm

Edit: Some quick math: 430 ohms at 3.7v = 0.032W power draw. Given a rated capacity of 56 AH, and assuming that the battery is 30% overcharged beyond the other cells (based on the range drop), that's a total of 16.8 extra AH in the battery. At a voltage of 3.7V, that's 62.16 WH in the cell. At .032W balancing draw, the car should fix itself after 1942 hours of operation--80 days nonstop.

Feel free to correct my math. If it's correct, I wouldn't want to rely on the BMS to balance those cells. Take the car to the dealer and have them fix it correctly.
This gibes with what has been stated elsewhere: that the BMS can only manage balancing when there isn't a huge difference in cell voltages. I hadn't realized that this was one of those cases. It would be interesting to see if it would happen eventually with this Leaf, but the best course of action for the OP seems to be to take it back - and warn them not to "fix" it by keeping the car for months of joyrides and L-2 charges.
Scarlet Ember 2018 Leaf SL W/ Pro Pilot
2009 Vectrix VX-1 W/18 Leaf modules, & 3 EZIP E-bicycles.
BAFX OBDII Dongle
PLEASE don't PM me with Leaf questions. Just post in the topic that seems most appropriate.

Lothsahn
Posts: 497
Joined: Thu Apr 05, 2018 4:35 pm
Delivery Date: 04 Jan 2018
Leaf Number: 007797

Re: Leaf range after battery module replacement

Fri Oct 11, 2019 1:10 pm

DaveinOlyWA wrote:
Fri Oct 11, 2019 11:37 am
Looks like a piss poor job of matching cells to the existing pack. Give it time, they will eventually self balance. Will likely take at least a month though.
Yes, but as per my math in an earlier statement, it'll be 80 days of operation (charging or discharging). With typical usage, this could be 2-4 years.
Last edited by Lothsahn on Fri Oct 11, 2019 1:18 pm, edited 1 time in total.
2011 Silver SV, purchased 2018, lives in Missouri (previously in CA)
LeafSpy Pro + BAFX Products OBDII dongle
Battery swap 2019/04/24 (87% SOH, 12 bar)

Lothsahn
Posts: 497
Joined: Thu Apr 05, 2018 4:35 pm
Delivery Date: 04 Jan 2018
Leaf Number: 007797

Re: Leaf range after battery module replacement

Fri Oct 11, 2019 1:17 pm

LeftieBiker wrote:
Fri Oct 11, 2019 12:46 pm
This gibes with what has been stated elsewhere: that the BMS can only manage balancing when there isn't a huge difference in cell voltages. I hadn't realized that this was one of those cases.
This is the "problem" of lithium batteries. Unlike alkaline, they have almost a flat discharge curve before they fall off quickly. A small voltage difference seems like nothing at all--in reality, it can be quite a bit of capacity.

That said, you're also right. While the owner noticed a 30% reduction in range, that should have been 200mv of delta, not 60mv[1]. It's possible the cells are bad too. Either way, take it back.

[1] https://pushevs.com/2018/01/29/2018-nis ... eal-specs/
2011 Silver SV, purchased 2018, lives in Missouri (previously in CA)
LeafSpy Pro + BAFX Products OBDII dongle
Battery swap 2019/04/24 (87% SOH, 12 bar)

nlspace
Posts: 48
Joined: Mon Jun 05, 2017 10:21 pm
Delivery Date: 06 Jun 2017

module charge balancer procedure

Sat Oct 12, 2019 8:39 am

OP @gary , found some info in the 2012 factory service manual that may be related to your issue. i can send you a 2-page .pdf file with this info if you want it.

In the FSM there is a procedure to adjust the voltage of a new module before installation using a special tool called a "module charge balancer" for that purpose.

Image

The procedure involves measuring the Max cell voltage of the pack to determine an adjustment value (AV) for the new module.
Then measure the new module voltage and discharge it below this AV.
Set the AV target value in the tool and start the adjustment.
At the end measure the voltage of the module and it should be equal to the AV target +/-10 mV.
Install the module and measure the difference between the installed module and the Max cell voltage, it should be within +/- 33 mV.

i don't have the 2018 FSM to compare, but it is likely the same sort of procedure. Unfortunately to repeat this would require opening the sealed pack cover.
Last edited by nlspace on Sat Oct 12, 2019 2:19 pm, edited 1 time in total.

DaveinOlyWA
Posts: 14149
Joined: Sat Apr 24, 2010 7:43 pm
Delivery Date: 16 Feb 2018
Leaf Number: 314199
Location: Olympia, WA
Contact: Website

Re: Leaf range after battery module replacement

Sat Oct 12, 2019 9:20 am

Lothsahn wrote:
Fri Oct 11, 2019 1:17 pm
LeftieBiker wrote:
Fri Oct 11, 2019 12:46 pm
This gibes with what has been stated elsewhere: that the BMS can only manage balancing when there isn't a huge difference in cell voltages. I hadn't realized that this was one of those cases.
This is the "problem" of lithium batteries. Unlike alkaline, they have almost a flat discharge curve before they fall off quickly. A small voltage difference seems like nothing at all--in reality, it can be quite a bit of capacity.

That said, you're also right. While the owner noticed a 30% reduction in range, that should have been 200mv of delta, not 60mv[1]. It's possible the cells are bad too. Either way, take it back.

[1] https://pushevs.com/2018/01/29/2018-nis ... eal-specs/
I see balancing in my cells nearly all the time including mid range SOC's when delta top to bottom is 10 mv or less and at lower SOC (below 15%) when deltas are in the mid 150's
2011 SL; 44,598 miles. 2013 S; 44,840 miles.2016 S30 deceased. 29,413 miles. 2018 S40; 15,000 miles, 478 GIDs, 37.0 kwh 109.81 Ahr , SOH 94.61, Hx 120.15
My Blog; http://daveinolywa.blogspot.com" onclick="window.open(this.href);return false;

Lothsahn
Posts: 497
Joined: Thu Apr 05, 2018 4:35 pm
Delivery Date: 04 Jan 2018
Leaf Number: 007797

Re: Leaf range after battery module replacement

Sat Oct 12, 2019 9:53 am

DaveinOlyWA wrote:
Sat Oct 12, 2019 9:20 am
I see balancing in my cells nearly all the time including mid range SOC's when delta top to bottom is 10 mv or less and at lower SOC (below 15%) when deltas are in the mid 150's
Yes, that's normal behavior. At high SOC's, small deltas in voltage indicate large capacity differences. At low SOC's, small deltas in voltage indicate small capacity differences. See the voltage curve of the Leaf cells I linked in an earlier post.

However, the user reported a 30% loss in capacity (based on range). The delta shown was 60mv at 78% SOC. Based on the voltage graph, that should be a 200mv delta for a 30% difference in capacity. That said, 60mv at 78% SOC is a large difference and the cells were either not balanced properly or defective or both.
2011 Silver SV, purchased 2018, lives in Missouri (previously in CA)
LeafSpy Pro + BAFX Products OBDII dongle
Battery swap 2019/04/24 (87% SOH, 12 bar)

coulomb
Posts: 64
Joined: Thu Oct 09, 2014 5:08 pm
Delivery Date: 07 Mar 2015
Leaf Number: 200445
Location: Brisbane, Australia

Re: Leaf range after battery module replacement

Sat Oct 12, 2019 9:12 pm

Lothsahn wrote:
Fri Oct 11, 2019 1:17 pm
This is the "problem" of lithium batteries. Unlike alkaline, they have almost a flat discharge curve before they fall off quickly.
It's LFP (LiFePO4) that has the really flat V vs SOC curve, actually two very flat regions with a small transition between them, which together cover well over half of the SOC range.

The Nissan cells do have more slope at higher SOC, in fact about 3 times (ignoring the knee at very low SOCs, which should be avoided anyway). But it's far from flat (as in horizontal) at any point. So it seems to me that SOC estimation is not terribly hard, given a decent voltage measurement.
At high SOC's, small deltas in voltage indicate large capacity differences. At low SOC's, small deltas in voltage indicate small capacity differences.
Um, at high SOC, a fixed delta in voltage indicates a small change in SOC (delta y fixed, high slope, small delta x). Are you saying that this small change in SOC somehow translates to a large change in capacity? Or did you just switch around the "small" and "large" adjectives by mistake?
2012 Leaf with new battery May 2019. New to me June 2019.

Lothsahn
Posts: 497
Joined: Thu Apr 05, 2018 4:35 pm
Delivery Date: 04 Jan 2018
Leaf Number: 007797

Re: Leaf range after battery module replacement

Sat Oct 12, 2019 11:18 pm

coulomb wrote:
Sat Oct 12, 2019 9:12 pm
Um, at high SOC, a fixed delta in voltage indicates a small change in SOC (delta y fixed, high slope, small delta x). Are you saying that this small change in SOC somehow translates to a large change in capacity? Or did you just switch around the "small" and "large" adjectives by mistake?
By high, I meant 75% (as shown in the picture). The slope of the curve is rather flat there--especially compared to the bottom 10% of the battery.

And I didn't say a small change in SOC translates to a large change in capacity. I said a small change in voltage at high SOC's (50-90%) translates to a large change in capacity. SOC drops linearly as charge is drawn from the battery, as it accounts for the voltage curves of the cells in the battery.

The curve is shown here:
https://pushevs.com/2018/01/29/2018-nis ... eal-specs/

Between 10 and 50 Ah, the voltage changes .3V, but that covers 72% of the capacity of the battery. Between 50 and 55Ah, the voltage changes .9V, despite only covering 9% of the capacity of the battery.
2011 Silver SV, purchased 2018, lives in Missouri (previously in CA)
LeafSpy Pro + BAFX Products OBDII dongle
Battery swap 2019/04/24 (87% SOH, 12 bar)

Return to “Range / Efficiency / Carwings”