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[Skidz]

Few days back I ran into an energy monitor (dlink 215 to be precise) and after finding out you don't need their crappy app and cloud but instead can use python to read and control the box, my inner nerd came out again and I graphed my loading curves for the last few days.

And the graphs made me wonder: Since the battery chemistry requires CC/CV loading, one would expect that as soon as the CV is hit, the current should decrease and a lower current should mean a lower power usage. But... My onboard charger ramps quickly to about 1220W, and the power consumption goes steadily up to 1400 watts untill it is abruptly cut off because it reaches 100%....

Is this expected behaviour?

[BrianTRice@gmail.com]

Well, first lengthen the time axis scaling there so you can see how abrupt it is. Each pixel seems like a half hour on the scale as presented, which will make a lot of behavior seem like a cliff.

Generally the charging cutback behavior I've heard of senses the battery voltage and cuts power back in increments when voltage reaches a certain level corresponding to 100%, and this usually cuts back to zero in a half hour or less.

[clockfort]

You're absolutely right about CC/CV, but you just need to keep in mind that 1.2kW is basically a trickle charge already for a 12kWh battery (~ 0.1C charge rate), which would make it hard to notice the slowdown at the end; it's pretty hard to notice the difference from ~12A from the charger into the battery from normal charging to when it goes down to 10A cutoff taper that it's set to by default.

This is combined with the fact that the Zeros by default don't let you charge the battery quite up to the maximum SoC, which limits the CV charge portion as well.

Battery charging log from MBB:

Code: [Select]

00027     07/20/2016 18:22:59   Module 00 Closing Contactor  vmod: 111.744V, maxsys: 111.740V, minsys: 111.740V, diff: 0.000V, vcap: 100.062V, prechg: 89%
 00028     07/20/2016 18:22:59   DEBUG: Module 00 Contactor is now Closed
 00029     07/20/2016 18:22:59   INFO:  Enabling Calex 720W Charger 0
 00030     07/20/2016 18:22:59   INFO:  Enabling Calex 1200W Charger 1
 00031     07/20/2016 18:22:59   INFO:  Enabling External Chg 0 Charger 2
 00032     07/20/2016 18:22:59   INFO:  Enabling External Chg 1 Charger 3
 00033     07/20/2016 18:23:06   Charging                   PackTemp: h 24C, l 24C, AmbTemp: 24C, PackSOC: 88%, Vpack:112.023V, BattAmps: -13, Mods: 10, MbbChgEn: Yes, BmsChgEn: No
 00034     07/20/2016 18:33:06   Charging                   PackTemp: h 24C, l 24C, AmbTemp: 25C, PackSOC: 89%, Vpack:113.069V, BattAmps: -12, Mods: 10, MbbChgEn: Yes, BmsChgEn: No
 00035     07/20/2016 18:43:06   Charging                   PackTemp: h 24C, l 24C, AmbTemp: 26C, PackSOC: 91%, Vpack:113.782V, BattAmps: -12, Mods: 10, MbbChgEn: Yes, BmsChgEn: No
 00036     07/20/2016 18:53:06   Charging                   PackTemp: h 25C, l 24C, AmbTemp: 26C, PackSOC: 92%, Vpack:114.443V, BattAmps:  -9, Mods: 10, MbbChgEn: Yes, BmsChgEn: No
 00037     07/20/2016 19:03:06   Charging                   PackTemp: h 25C, l 25C, AmbTemp: 25C, PackSOC: 94%, Vpack:115.027V, BattAmps: -11, Mods: 10, MbbChgEn: Yes, BmsChgEn: No
 00038     07/20/2016 19:13:06   Charging                   PackTemp: h 25C, l 25C, AmbTemp: 24C, PackSOC: 95%, Vpack:115.645V, BattAmps: -12, Mods: 10, MbbChgEn: Yes, BmsChgEn: No
 00039     07/20/2016 19:23:05   Charging                   PackTemp: h 26C, l 25C, AmbTemp: 24C, PackSOC: 97%, Vpack:116.317V, BattAmps: -11, Mods: 10, MbbChgEn: Yes, BmsChgEn: No
 00040     07/20/2016 19:33:06   Charging                   PackTemp: h 27C, l 25C, AmbTemp: 23C, PackSOC: 99%, Vpack:117.037V, BattAmps: -10, Mods: 10, MbbChgEn: Yes, BmsChgEn: No
 00041     07/20/2016 19:43:06   Charging                   PackTemp: h 27C, l 25C, AmbTemp: 23C, PackSOC:100%, Vpack:116.966V, BattAmps:   0, Mods: 10, MbbChgEn: Yes, BmsChgEn: No
 00042     07/20/2016 19:53:06   Charging                   PackTemp: h 28C, l 26C, AmbTemp: 22C, PackSOC:100%, Vpack:116.884V, BattAmps:   0, Mods: 10, MbbChgEn: Yes, BmsChgEn: No
 00043     07/20/2016 20:03:06   Charging                   PackTemp: h 28C, l 26C, AmbTemp: 22C, PackSOC:100%, Vpack:116.840V, BattAmps:   0, Mods: 10, MbbChgEn: Yes, BmsChgEn: No
 00044     07/20/2016 20:13:06   Charging                   PackTemp: h 29C, l 26C, AmbTemp: 22C, PackSOC:100%, Vpack:116.813V, BattAmps:   0, Mods: 10, MbbChgEn: Yes, BmsChgEn: No
 00045     07/20/2016 20:23:06   Charging                   PackTemp: h 29C, l 26C, AmbTemp: 22C, PackSOC:100%, Vpack:116.793V, BattAmps:   0, Mods: 10, MbbChgEn: Yes, BmsChgEn: No

Charger information over CANBUS:

Code: [Select]

***********  Charger #1  *************
  - Charger Name              : Calex 1200W
  - Attached                  : Yes
  - Enabled                   : Yes
    CAN RX
    - Status Bits             :   0x0080
       - Charging
    - Present Voltage         : 112.502 V
    - Present Current         :  12.132 A
    - Max Voltage Capable     : 116.400 V
    - Max Current Capable     :  65.535 A
    - Time since CAN RX       :    56 ms
    - Age of status data      :    69 ms
    - Age of max data         :    78 ms
    CAN TX
    - Max Voltage Allowed     : 116.400 V
    - Max Current Allowed     :  65.535 A
    - Current Taper Cutoff    :  10.000 A


[clockfort]

fwiw, chargepoint's current loops do notice the slowdown at the end, but only for a single time period frame.

[BrianTRice@gmail.com]

clockfort's data and description of cutback for the onboard charger looks right to me. Notice the battery voltage reading just as current goes from 12A, to 11A, then 10A, and then cuts out entirely.

Anyway, I wrote this up for the manual now: http://zeromanual.com/index.php/Unofficial_Service_Manual#Charger

[Skidz]

Ow crap, didn't calculate the scale of things into the equasion I have experience with a bit smaller LiPo chemistry batteries (66Ah range) so indeed 12 amps looks like 0.1C charging... I just sort-of expected the cell balancing to use more than the 3 watts I'm reading after the charge finishes. Guess the BMS balances the cells during the charging then.

Ow, and about the scale: I log the watts going in every 5 minutes, and over the course of 10 minutes the charging goes from 1400 to 600 to 0 watts.

[nigezero]

Yep, I log my circuits every 5 seconds and this image shows the same rapid drop off but also a few more changes. There's also a recurring bump for a few hours afterward but can't tell if that's the charger.

[BrianTRice@gmail.com]

Yep, I log my circuits every 5 seconds and this image shows the same rapid drop off but also a few more changes. There's also a recurring bump for a few hours afterward but can't tell if that's the charger.

That is definitely the charger, waking up once in a while to balance the cells by applying current in a directed way through the interconnects inside the monolith casing that reach into each brick.