SimpBMS Tesla pack expansion tripping offline

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freds

New member
Joined
Dec 3, 2019
Messages
10
I have been running with SimpBMS in my bus/motorhome for two years with a few problems.

I recently had a malfunction with the pre-charge circuit that caused the positive contactor to weld shut and over discharge my pack.

One of my previous two Tesla modules didn't recover from this event. So I decided to expand my pack to five modules by buying four more modules.

I am running the five modules in parallel as I have a high power 24V inverter.

In the new pack build I switched to Tesla Gigavac contactors.
1637355650099.jpeg

The problem that I am experiencing is that the SimpBMS is tripping the contactors offline when I put greater than a 2KW load on the pack.

On my new pack I added LED indicators to indicate relay status and on startup I see the negative contactor and pre-charge contactor turn on first, followed by pre-charge turning off and the positive contactor turning on.

When the 2KW load is started it runs for about one second and then the indicators for both the positive and negative contactors goes off.

Here's some serial output detail and configuration detail:

BMS Status : 2 Drive | AC Present || Key ON | 30
Out:1001 Cont:1100 In:1010 Charge Current Limit : 174 A DisCharge Current Limit : 300 A

1 - Cell Over Voltage Setpoint: 4200mV
2 - Cell Under Voltage Setpoint: 3000mV
3 - Over Temperature Setpoint: 65.00C
4 - Under Temperature Setpoint: -10.00C
5 - Cell Balance Voltage Setpoint: 3200mV
6 - Balance Voltage Hystersis: 40mV
7 - Ah Battery Capacity: 1200Ah
8 - Pack Max Discharge: 300.00A
9 - Cell Discharge Voltage Limit Setpoint: 3200mV
0 - Slave strings in parallel: 5
a - Cells in Series per String: 6
b - setpoint 1: 3100mV
c - SOC setpoint 1:10%
d - setpoint 2: 4100mV
e - SOC setpoint 2: 90%
g - Storage Setpoint: 3800mV
h - Discharge Current Taper Offset: 300mV
j - Discharge Current Temperature Derate : 40.00C
k - Cell Discharge Voltage Hysteresis: 200mV

Code:
Initial Status on power up:



Modules: 5 Cells: 30 Strings: 5  Voltage: 23.543V   Avg Cell Voltage: 3.924V  Low Cell Voltage: 3.918V   High Cell Voltage: 3.945V Delta Voltage: 27mV   Avg  Temp: 8.267C

Module #1   23.54V   Cell0: 3.92V   Cell1: 3.92V   Cell2: 3.92V   Cell3: 3.92V  Cell4: 3.92V   Cell5: 3.92V  Neg Term Temp: 8.76C  Pos Term Temp: 7.44C
Module #2   23.54V   Cell6: 3.92V   Cell7: 3.92V   Cell8: 3.92V   Cell9: 3.92V  Cell10: 3.92V  Cell11: 3.92V  Neg Term Temp: 8.66C  Pos Term Temp: 7.31C
Module #3   23.55V  Cell12: 3.92V  Cell13: 3.92V  Cell14: 3.92V  Cell15: 3.92V  Cell16: 3.93V  Cell17: 3.92V  Neg Term Temp: 8.99C  Pos Term Temp: 7.35C
Module #4   23.54V  Cell18: 3.92V  Cell19: 3.92V  Cell20: 3.92V  Cell21: 3.92V  Cell22: 3.92V  Cell23: 3.92V  Neg Term Temp: 9.01C  Pos Term Temp: 7.82C
Module #5   23.54V  Cell24: 3.92V  Cell25: 3.92V  Cell26: 3.94V  Cell27: 3.92V  Cell28: 3.92V  Cell29: 3.92V  Neg Term Temp: 9.09C  Pos Term Temp: 8.24C
CANbus   -6498.30mA  75% SOC 4559801.00mAh
 

Status after turning on inverter:


Modules: 5 Cells: 30 Strings: 5  Voltage: 23.523V   Avg Cell Voltage: 3.920V  Low Cell Voltage: 3.914V   High Cell Voltage: 3.940V Delta Voltage: 26mV   Avg Temp: 8.262C

Module #1   23.52V   Cell0: 3.92V   Cell1: 3.92V   Cell2: 3.92V   Cell3: 3.92V   Cell4: 3.92V   Cell5: 3.92V  Neg Term Temp: 8.74C  Pos Term Temp: 7.44C
Module #2   23.52V   Cell6: 3.92V   Cell7: 3.92V   Cell8: 3.92V   Cell9: 3.92V  Cell10: 3.92V  Cell11: 3.92V  Neg Term Temp: 8.66C  Pos Term Temp: 7.31C
Module #3   23.52V  Cell12: 3.92V  Cell13: 3.92V  Cell14: 3.92V  Cell15: 3.92V  Cell16: 3.92V  Cell17: 3.92V  Neg Term Temp: 8.98C  Pos Term Temp: 7.35C
Module #4   23.52V  Cell18: 3.92V  Cell19: 3.92V  Cell20: 3.92V  Cell21: 3.92V  Cell22: 3.92V  Cell23: 3.92V  Neg Term Temp: 9.00C  Pos Term Temp: 7.82C
Module #5   23.52V  Cell24: 3.92V  Cell25: 3.91V  Cell26: 3.94V  Cell27: 3.91V  Cell28: 3.92V  Cell29: 3.92V  Neg Term Temp: 9.08C  Pos Term Temp: 8.24C
CANbus   -16089.37mA  75% SOC 4559754.00mAh


Messages after turning on 2KW load:



Modules: 5 Cells: 30 Strings: 5  Voltage: 23.448V   Avg Cell Voltage: 3.908V  Low Cell Voltage: 3.901V   High Cell Voltage: 3.926V Delta Voltage: 24mV   Avg Temp: 8.246C

Module #1   23.44V   Cell0: 3.91V   Cell1: 3.91V   Cell2: 3.91V   Cell3: 3.91V   Cell4: 3.91V   Cell5: 3.91V  Neg Term Temp: 8.71C  Pos Term Temp: 7.43C
Module #2   23.45V   Cell6: 3.91V   Cell7: 3.91V   Cell8: 3.91V   Cell9: 3.91V  Cell10: 3.91V  Cell11: 3.91V  Neg Term Temp: 8.64C  Pos Term Temp: 7.29C
Module #3   23.44V  Cell12: 3.91V  Cell13: 3.91V  Cell14: 3.91V  Cell15: 3.91V  Cell16: 3.91V  Cell17: 3.91V  Neg Term Temp: 8.96C  Pos Term Temp: 7.34C
Module #4   23.45V  Cell18: 3.91V  Cell19: 3.91V  Cell20: 3.91V  Cell21: 3.91V  Cell22: 3.91V  Cell23: 3.91V  Neg Term Temp: 8.99C  Pos Term Temp: 7.81C
Module #5   23.45V  Cell24: 3.91V  Cell25: 3.90V  Cell26: 3.93V  Cell27: 3.90V  Cell28: 3.90V  Cell29: 3.90V  Neg Term Temp: 9.07C  Pos Term Temp: 8.22C
CANbus   -43369.23mA  75% SOC 4559417.00mAh


Modules: 5 Cells: 30 Strings: 5  Voltage: 23.341V   Avg Cell Voltage: 3.890V  Low Cell Voltage: 3.882V   High Cell Voltage: 3.904V Delta Voltage: 22mV   Avg Temp: 8.249C

Module #1   23.33V   Cell0: 3.89V   Cell1: 3.89V   Cell2: 3.89V   Cell3: 3.89V   Cell4: 3.89V   Cell5: 3.89V  Neg Term Temp: 8.72C  Pos Term Temp: 7.44C
Module #2   23.36V   Cell6: 3.89V   Cell7: 3.89V   Cell8: 3.89V   Cell9: 3.89V  Cell10: 3.89V  Cell11: 3.90V  Neg Term Temp: 8.64C  Pos Term Temp: 7.31C
Module #3   23.33V  Cell12: 3.89V  Cell13: 3.89V  Cell14: 3.89V  Cell15: 3.89V  Cell16: 3.89V  Cell17: 3.89V  Neg Term Temp: 8.96C  Pos Term Temp: 7.34C
Module #4   23.36V  Cell18: 3.89V  Cell19: 3.89V  Cell20: 3.89V  Cell21: 3.89V  Cell22: 3.89V  Cell23: 3.89V  Neg Term Temp: 8.99C  Pos Term Temp: 7.81C
Module #5   23.33V  Cell24: 3.89V  Cell25: 3.88V  Cell26: 3.90V  Cell27: 3.88V  Cell28: 3.89V  Cell29: 3.89V  Neg Term Temp: 9.06C  Pos Term Temp: 8.22C
CANbus   -100246.58mA  75% SOC 4559409.50mAh



Modules: 5 Cells: 30 Strings: 5  Voltage: 23.321V   Avg Cell Voltage: 3.887V  Low Cell Voltage: 3.879V   High Cell Voltage: 3.901V Delta Voltage: 22mV   Avg Temp: 8.252C

Module #1   23.30V   Cell0: 3.89V   Cell1: 3.88V   Cell2: 3.88V   Cell3: 3.88V  Cell4: 3.88V   Cell5: 3.89V  Neg Term Temp: 8.72C  Pos Term Temp: 7.44C
Module #2   23.34V   Cell6: 3.89V   Cell7: 3.89V   Cell8: 3.89V   Cell9: 3.89V  Cell10: 3.89V  Cell11: 3.89V  Neg Term Temp: 8.64C  Pos Term Temp: 7.31C
Module #3   23.31V  Cell12: 3.89V  Cell13: 3.88V  Cell14: 3.88V  Cell15: 3.88V  Cell16: 3.88V  Cell17: 3.89V  Neg Term Temp: 8.96C  Pos Term Temp: 7.34C
Module #4   23.34V  Cell18: 3.89V  Cell19: 3.89V  Cell20: 3.89V  Cell21: 3.89V  Cell22: 3.89V  Cell23: 3.89V  Neg Term Temp: 8.99C  Pos Term Temp: 7.81C
Module #5   23.32V  Cell24: 3.89V  Cell25: 3.88V  Cell26: 3.90V  Cell27: 3.88V  Cell28: 3.89V  Cell29: 3.88V  Neg Term Temp: 9.08C  Pos Term Temp: 8.24C
CANbus   -103156.43mA  75% SOC 4559394.00mAh


Modules: 5 Cells: 30 Strings: 5  Voltage: 23.313V   Avg Cell Voltage: 3.886V  Low Cell Voltage: 3.878V   High Cell Voltage: 3.900V Delta Voltage: 22mV   Avg Temp: 8.250C

Module #1   23.29V   Cell0: 3.88V   Cell1: 3.88V   Cell2: 3.88V   Cell3: 3.88V   Cell4: 3.88V   Cell5: 3.88V  Neg Term Temp: 8.72C  Pos Term Temp: 7.43C
Module #2   23.33V   Cell6: 3.89V   Cell7: 3.89V   Cell8: 3.89V   Cell9: 3.89V   Cell10: 3.89V  Cell11: 3.89V  Neg Term Temp: 8.64C  Pos Term Temp: 7.31C
Module #3   23.31V  Cell12: 3.89V  Cell13: 3.88V  Cell14: 3.88V  Cell15: 3.88V  Cell16: 3.88V  Cell17: 3.89V  Neg Term Temp: 8.96C  Pos Term Temp: 7.34C
Module #4   23.33V  Cell18: 3.89V  Cell19: 3.89V  Cell20: 3.89V  Cell21: 3.89V  Cell22: 3.89V  Cell23: 3.89V  Neg Term Temp: 8.99C  Pos Term Temp: 7.81C
Module #5   23.31V  Cell24: 3.89V  Cell25: 3.88V  Cell26: 3.90V  Cell27: 3.88V  Cell28: 3.88V  Cell29: 3.88V  Neg Term Temp: 9.07C  Pos Term Temp: 8.24C
CANbus   -102507.52mA  75% SOC 4559379.00mAh


Modules: 5 Cells: 30 Strings: 5  Voltage: 23.479V   Avg Cell Voltage: 3.913V  Low Cell Voltage: 3.908V   High Cell Voltage: 3.932V Delta Voltage: 25mV   Avg Temp: 8.252C

Module #1   23.47V   Cell0: 3.91V   Cell1: 3.91V   Cell2: 3.91V   Cell3: 3.91V  Cell4: 3.91V   Cell5: 3.91V  Neg Term Temp: 8.73C  Pos Term Temp: 7.44C
Module #2   23.48V   Cell6: 3.91V   Cell7: 3.91V   Cell8: 3.91V   Cell9: 3.91V  Cell10: 3.91V  Cell11: 3.91V  Neg Term Temp: 8.64C  Pos Term Temp: 7.31C
Module #3   23.48V  Cell12: 3.91V  Cell13: 3.91V  Cell14: 3.91V  Cell15: 3.91V  Cell16: 3.91V  Cell17: 3.91V  Neg Term Temp: 8.96C  Pos Term Temp: 7.34C
Module #4   23.48V  Cell18: 3.91V  Cell19: 3.91V  Cell20: 3.91V  Cell21: 3.91V  Cell22: 3.91V  Cell23: 3.91V  Neg Term Temp: 8.99C  Pos Term Temp: 7.81C
Module #5   23.48V  Cell24: 3.91V  Cell25: 3.91V  Cell26: 3.93V  Cell27: 3.91V  Cell28: 3.91V  Cell29: 3.91V  Neg Term Temp: 9.07C  Pos Term Temp: 8.24C
CANbus   -5991.48mA  75% SOC 4559367.50mAh


Note: The last reported current is after the positive and negative contactors have tripped offline and reflects a smart battery charger and the solar charge controllers that have their own automatic disconnects in my system.

Any ideas on how to diagnose this problem? When I had two Tesla modules I was able to draw much more power with no problems.
 
Last edited:

Redpacket

Member
Joined
Feb 28, 2018
Messages
1,330
Doesn't look like anything under voltage or over current there.
Can you use a smaller load & increase in steps to see if you can catch something different?
Are these with replaced contactors?
Any chance there's a poor junction with bus bars/cables, etc?
Are the connections to the SimBMS controller solid too?
 

freds

New member
Joined
Dec 3, 2019
Messages
10
Doesn't look like anything under voltage or over current there.
Can you use a smaller load & increase in steps to see if you can catch something different?
Are these with replaced contactors?
Any chance there's a poor junction with bus bars/cables, etc?
Are the connections to the SimBMS controller solid too?
Everything is fairly fresh connections and yes this is with the new contactors.

One additional datum immediately after installation it did handle a 4KW load.

The weirdness is that both contactors have gone offline each time.

I am using it with a Victron color computer it's loosing power immediately as the BMS tripped offline. Going to independently power it and see if it catches anything.
 

CarelHassink

Member
Joined
Oct 21, 2017
Messages
154
Hmm, nothing too intelligent, but since this is a new battery pack, and there was this major incident with the old pack>>
perhaps start from scratch with a new flashed firmware. or even a new teensy 3.2, and take it from there to re-build your battery

best Carel
 

Redpacket

Member
Joined
Feb 28, 2018
Messages
1,330
Would the wiring have changed much, eg a ground/0V or +ve rail point for the SimBMS controller have moved eg controller supply picking up inverter noise vs old connections?
+1 having control system powered to stay on is a good idea.
 

freds

New member
Joined
Dec 3, 2019
Messages
10
Ok yes it was ultimately the new pack wiring configuration.

Have a friend who is down on his luck, so can only afford one Tesla module after buying the other stuff needed for his Boone docking/solar system.

Anyway I am working on a discreet wired version of the BMS using stuff ordered from Amazon for approximately 20% of the cost of the SimpBMS once you order it from overseas.

Anyway part of the new layout is using DC to DC SSR's to drive the contactors. Once I changed the contactor configuration PWM value to 255 everything started working as expected and I was able to pull my expected 6KW maximum load. So the DC to DC SSR's didn't like being driven by a PWM signal.

To help my friend; I am doing two stage checkout/development starting with the SimpBMS and then doing the other discreet components to ultimately replace it.

Turns out my other Tesla module starting acting up after a few high power cycles, opps!!! So now running with the four new modules and will order a fifth this week to fill out my rack.
 

Redpacket

Member
Joined
Feb 28, 2018
Messages
1,330
Ok yes it was ultimately the new pack wiring configuration.

Have a friend who is down on his luck, so can only afford one Tesla module after buying the other stuff needed for his Boone docking/solar system.

Anyway I am working on a discreet wired version of the BMS using stuff ordered from Amazon for approximately 20% of the cost of the SimpBMS once you order it from overseas.

Anyway part of the new layout is using DC to DC SSR's to drive the contactors. Once I changed the contactor configuration PWM value to 255 everything started working as expected and I was able to pull my expected 6KW maximum load. So the DC to DC SSR's didn't like being driven by a PWM signal.

To help my friend; I am doing two stage checkout/development starting with the SimpBMS and then doing the other discreet components to ultimately replace it.

Turns out my other Tesla module starting acting up after a few high power cycles, opps!!! So now running with the four new modules and will order a fifth this week to fill out my rack.
Great, glad you got it figured out.
+1 SSR's like DC drive not PWM.
Sucks that the Tesla packs got toasted!
 
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