Programming Outputs on REC BMS

[areddon]

I have a split bus system for a 12 volt, 400 Ah LiFePO4 house bank on my sailboat. The bank comprises 16 105 Ah EVE cells, 4P4S (4S4P? ... I can never remember ... anyway its 4 cells in paralell then those joined in series).

I charge to 3.6 volts and then hold there until current drops to 20 Amps (0.05C).

Using the REC BMS I have the CHG relay set up to disconnect the bank from the charge buss if any cell reaches 3.7 volts (14.8 for pack). There is a 6 second delay and I have other means to shut off the field current to the alternator during that delay if ever the REC opens the CHG relay.

I have the REC DCH relay set up to disconnect the pack from the load buss if any cell falls to 2.9 volts (11.6 volts for pack).

All good. Here is my problem:

I want to use one of the octocouplers to trip a high voltage warning buzzer if any cell reaches 3.65 volts and use the other octocoupler to trip a low voltage warning buzzer if any cell falls to 3.15 volts (11.6 pack). Obviously I want to have some notice of impending disconnect.

REC advertising materials say these outputs are "user programmable". I am pretty inexperienced with this stuff and find the REC manual a bit confusing.

Questions:
1) Is there a way to program the two octocoupler outputs in this way?
2) Any comment about or disagreement with the voltage thresholds I am considering?

 

[nebulight]

I assume you have an active BMS. Do you have the wifi module or do you use the PC software for programming? If you have neither, you can get an opensource module from aaronb https://github.com/aaronsb/REC-BMSManager. wifi module will be much easier if you are a novice as it's a whole screen in the wifi module. With the PC software or Aaron's module require a bit more. From the ABMS manual:

ABMS Outputs Settings:System devices can be controlled by digital outputs Charge optocoupler and optocoupler 2 and relay1. Charge optocoupler is already pre-programmed as charge sources control, while optocoupler 2 andrelay 1 can be user programmed. Relay 1 hysteresis RE1H and optocoupler 2 hysteresis OP2H play therole of top disconnect or bottom disconnect. If the hysteresis is set positive the output will bottomdisconnect, while if negative it will top disconnect.Errors 4, 5, 8, 10, 11, 12 and 13 disconnect relay 1 and optocoupler 2.EXAMPLE 1:We want to use relay 1 as battery charge control. Relay 1 should switch off if the highest cell reaches3.65 V with 0.15 V hysteresis. In communicate window we set:RE1L 3.65RE1H -0.15

Also, the optocouplers are VERY low current (I think around 15ma). so you really probably can't power a buzzer directly. You'll need an additional relay or something low current to power the buzzer.

 

[areddon]

Thank you for responding.

I do have active BMS and use the PC software.

Relay 1 and Relay 2 are being used to control main contactors so only the octocouplers are available for warning buzzers.

My manual has language about the optocouplers which differs from the one you quoted. My manual says:

"Charge optocoupler 1
Charge optocoupler 1 may be programmed to function in three ways. As a charger enable signal(Charge optocoupler 1 hysteresis OP1H is set to 0, OP1L is irrelevant in this case). If OP1H hysteresisis set to a positive value, digital output functions as an under-voltage protection – OP1L should be setto a threshold voltage level under which the output turns off.

If OP1H hysteresis is set to a negative value, digital output functions as an over-voltage protection –OP1L should be set to a threshold voltage level over which the output turns off.

Discharge optocoupler 2

Discharge optocoupler 2 may be programmed to function in two ways only. If OP2H hysteresis is setto a positive value, digital output functions as an under-voltage protection – OP2L should be set to athreshold voltage level under which the output turns off.
If OP2H hysteresis is set to a negative value, digital output functions as an over-voltage protection –OP2L should be set to a threshold voltage level over which the output turns off.

If OP2H hysteresis is set to 0, output is disabled."

Q1: Am i right that if i program OP1 with my desired low voltage alarm threshold, and positive hyteresis the output will "turn off" when voltage goes below the threshold?

Q2: Am I right that programming OP 2 with high alarm threshold and negative hysteresis will cause the output to "turn off" the when voltage goes above.

Q3: what does it mean for the output to "turn off"? Does that effectively mean it stops providing a path to ground so that a relay will go to its "normal" position, whether NO or NC?

Thanks for your help