Low Temperature Charging Prevented (Wakespeed 500+Cerbo+REC Q)

• N

  Nathaniel

  11/29/23, 12:51 PM

  Today I encounted a problem where the wakespeed would not charge under low temperature conditions.  It appears that either the REC is sending a CAN message in error, or the Wakespeed is interpreting a CAN message in error.

  ERROR: Wakespeed was reporting error 61 which the comm spec describes as "A CAN command has been received asking for the battery bus to be disconnected". 

  This error was also being reported on the CERBO coming from the Wakespeed as an ALARM.  The CERBO also a reported a "Low Charge Temperature" WARNING from the REC BMS.  These are stamped to the same minute, which makes me think that the Wakspeed might be misinterpreting a warning as an alarm with a pending disconnect.
  
  Conditions:

  • All battery cell temperatures were >= 7C
  • SOC ≈37%
  • REC BMS was reporting a healthy Current Charge Limit (> 100A) via CAN

  BMS Settings:

  • "Minimum allowed temperature for charging" = 5C

  Wakespeed Settings:

  • CPF Parameter 2 - Value '5' - disables charging if battery temp below 5C (default was 2, set to 5 to match REC)
  • CPF Parameter 5 - Value '7' - if battery temp =< 7C, enter reduced charge mode (default was 5, set to 7 to coordinate with REC)

  In the course of troubleshooting I applied heat to the wakespeed temperature sensor to ensure it was above 7C, to no effect.  I restarted the wakespeed, but the error locked in again, suggesting something was still actively being reported on CAN.  To solve the problem temporarily to allow charge, I dropped the REC minimum allowed temperature to 0C, at which point the error cleared both on the wakespeed and the CERBO and charging commenced.

  I'm hoping @Al Thomason  and/or @Tine Andrejasic  and/or @Rick Admin  can speak to this issue and clarify whether this might lie with Wakespeed or REC. 

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• A

  Al

  11/30/23, 11:45 AM

  Disclaimer -- Al from Wakespeed.
   
  What fun!   OK, to step back a bit:  When it comes to temperature of the battery there are perhaps two details to keep in mind:
  1) Battery Temp may be delivered via CAN, or using a dedicated BTS sensor.   IF a BTS is installed, it will override the CAN delivered value.  That there can cause for issues:  the BMS working with one value (based on the BMS Sensors), and the Wakespeed working with a different value (Based on its BTS).  Perhaps a suggestion is to not install the BTS sensor, instead using the single value from the REC BMS.  (You can also toggle on 'Ignore BTS' if you wish)
  2) With regards to how the Wakespeed works when we are in slave mode:  With the exception of the $CPB parameters, all other Charge Profile $CPx values are disregarded, the BMS controls the shots.   The $CPB is left active as a kind of 'Dbl' check fo the BMS for conditions such as Temperature limits, as well as if the installer wishes to override the BMS C rate ask, with a lower max charge current.  All those are defined in the $CPB command
  Now, to your condition:   IF the Wakespeed has its CPB command with defined tempeture limits, when those are reached and exceeded (High, low), the WS500 will enter a standby state -- disabling charging but not faulting out.  What seems to be happening in your case is the BMS is sending  its Alarms/Warning CAN message Low-temperture bit set.

  
  The REC / Wakespeed CAN communications is based on SMA, and the message in question is the Alarms/Protection message (0x35A).  It is kind of hard to get a spec document, but if you google this I found a PDF that contained the details:  "Technical Information Connecting Batteries with external Battery Management System to SUNNY ISLAND 6.0H-11"
  You want the one that comes up as "sma-can-protocol.pdf"

  
  In there we look at section 5.2, and specifically the Alarm Messages.   -- Packet 0x35A
   
  FLT 61: FC_CAN_BATTERY_LT_DISCONNECTED   is triggered by any of the "Battery Low Temp" condition as sent by the BMS.  Note there are two 'classes':  Alarms, and Warnings   In the case of Alarms, this is intended as a precursor for a BMS disconnect (And where we work with the likes of REC to assure this message arrives in time to allow safe shutdown of the Alterantor).  The WS500 issues a FLT code, and then enteres its fault state.   Requiring power-cycling.  Warning will also cause the Wakespeed to issue a fault, but then auto-reset.

   

  
  Example: 
    Alarm Low Temperature (Byte 1, Bit pair 0/1) will toss a FLT 61 and require power-cycling (Unless you enable 'Promiscuous Mode' to override the Hard Faults and treat them as soft-faults with auto-restart)
    Warning Low Temperature (Byte 5, Bit pair 0/1) will toss a FLT 61, and then auto-restart the regulator.

  In your case, editing the CPB paramaters will indeed have an impact on operations -- but not tossing a fault.  FLT 61 comes from the BMS via CAN You may well be able to tune the REC settings to better match how you want the systm to behave. 

  I hope this gives some insight into how the two products interact, and some idea on how to proceed!

  
   

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• N

  Nathaniel

  12/1/23, 12:54 AM

  @Al 

  A few notes/corrections regarding my post:

  I mistakenly listed my wakespeed settings as CPF parameters...that was a mistake, so they are programmed correctly as CPB.  I think you picked up on that, but to avoid confusion for anyone else reading, corrected they are:

  • CPB Parameter 2 - Value '5' - disables charging if battery temp below 5C (default was 2, set to 5 to match REC)
  • CPB Parameter 5 - Value '7' - if battery temp =< 7C, enter reduced charge mode (default was 5, set to 7 to coordinate with REC)

  During initial system design I decided to use the wakespeed temperature sensor, and those parameters as a "hardware backup" in the event something went awry with CAN communication.  Per my read of the manual (at least back then), the wakespeed will conservatively prioritize its sensor over CAN, in slave mode, and limit/stop charging if its sensor hits the CPB values.  I took this to mean that if either CAN OR the wakespeed temp sensor + CPB call for limit or stop, it will limit or stop.  Is this the case?

  In any case, I'm quite sure that once I had a heat gun on the wakespeed sensor, it was well above my CPB set points.  Meanwhile the lowest BMS sensor was 7.5C, so those were also above my CPB setpoints.  Yet charging would not resume and the wakespeed remained faulted.  When I lowered the BMS minimum charge parameter, while everything was online, from 5C to 0C, the wakespeed stopped flashing the LED code for the fault, and started charging.  I don't recall seeing anything indicative of a reset, but I'm not sure I would have been able to.  Also, I do NOT have promiscuous mode enabled:

  • SCO Parameter 6 - Value '0' - Promiscuous mode, default = 0, 1 allows self reset of many faults without power cycle, new in firmware 2.5

  It seems clear to me from where the temperatures were, the BMS should have been issuing the low temperature WARNING and not the ALARM.  If I understand you correctly, in either case (WARNING or ALARM) the Wakespeed will send the same FLT61 down the CAN, but its behavior will be different in each case (hard fault for the ALARM, auto-recover for the WARNING).  Is that right?

  Can you clarify the operation in the case of the WARNING?  Specifically, does the auto-restart of the regulator occur only after the WARNING clears?  Meaning that while the WARNING is active, it will not charge?  That behavior would be consistent with what I witnessed since I don't have promiscuous mode enabled.

  Thanks,

  Nate

  PS: I recently watched your video on wakespeed history.  Love that the original 100 was for wakeboarding soundsystems.  Great stuff, and a great video!

   

   

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• A

  Al

  12/5/23, 5:41 PM

  @Nathaniel

  CPF vs CPB, lol ..  no worries!   Yes,  when the WS500 is in 'Slave' mode, all the CPx values are ignored, except those of CPB.  You can set the CPB values to 'Don't apply' if wished and just use the BMS directions, or for example sometimes folks want to set a max charge rate less then 0.5C, even if the BMS asks for it, and the CPB lets you.

  Now, in the case of the REC -- kind of not really needed, in that you as an installer have the ability to fully control the REC BMS settings; this whole CPB detail is more for installs where the BMS is closed.  Example, Lithionics installs.

  But back to how the BMS + CPB interact:  If the BMS says 'Stop Charge', we will.  If one of the CPB limits is exceeded, charging will stop - - whoever is more restrictive wins.   Now in the case of Battery Temperature limits being reached, the WS500 (based on a CPB limit) stop the charge process and cycle.  Going back to pre-ramp, and on.  If during that time the battery say warms up, then charging can resume upon recycling.  But if the battery is still too cold (or hot), the charge process will again be cycled.  I hope this makes sense.

  If the BMS is asking for a stop charge, the WS500 will stop charging.  And this is how normal behavior should work.  The CAN messages have in them a 'Allowed to Charge', as well as a way to signal Stop Charging -- think when the SOC reached 100%    In this normal operation, no fault it tossed.  Charging just stops, the reg stays in standby mode until the BMS ask for charging again.

  But there is also a class of Alarms and Protection messages.  Different folks call them by different names:  Warning, Alarms, Protection; but these are all in a class of not normal situations.   The BMS is stressed, something is doing things that should not happen (Common for us is Solar charging past when it should stop).  These cause a Fault.   Either Hard or Soft, but a fault none the less.  Should not happen and largely indicates a deficiency in the system design.  Here is the details Soft vs. Hard Faults differ from each BMS.  For the Wakespeed, we parse ‘warnings’ as soft faults, which toss the error and reset.  Hard’s toss the fault and need power-cycling (unless Promiscuous mode is enabled which will cause hard faults to also auto-reset)

  I would suggest in your case:  Take log files from the Wakespeed and compare things relative to what the BMS is telling ya.   All up to you to set how to define things between the WS500 and the BMS.   Always fun!

  Note sure if this helps ya or not.   Do hope so.

   

   

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