Whiz Bang Senior

[boB]

https://www.multitel.com/

They already do Float current monitoring. (FCCP)
They also do modbus to snmp conversions. https://www.multitel.com/solutions/modbus-snmp-protocol-conversion/

I know little of communications protocols.

1. If a stand alone "WBsenior" had a modbus connection, could it communicate with MidNite charge controllers?

2. For my own info, could multiple op amps be connected to the same SHUNT. (my best guess is Yes)

Thanks for your input. Barry

Yes and yes

We were thinking about doing snmp at one time

[Barry Fields]

two questions if I may.
1. the WBjr circuit board is designed to work only with a 500a 50mv shunt. I do not see adjustments for other shunts.

2. Am I correct in saying that MODBUS only describes the interconnection of units. SPI and uart can be used on that buss? If so what serial protocol does Midnite use?

Please edumacate me.

Thanks Barry

[boB]

The WbJr has programmable gain and is turned up all the way for 50mV/500A. That means it will work for smaller shunts but adjustments would have to be made on the Classic.

It works the way it is now with any scaling of that 50mV/500A.  We also use 100mV/1000A and 200mV/2000A as is. Good to 2500A DC.

The serial protocol is ours but basically 8 bits 1200 baud command and then the WbJr responds with the values and CRC. Simple. In between commands, the WbJr is powered by the Classic.

[Barry Fields]

I hear you saying that any ADC wishing to communicate would need to be programed with MidNite's serial protocol.
Is the same protocol used with all MidNite's charge controllers?

[boB]

I hear you saying that any ADC wishing to communicate would need to be programed with MidNite's serial protocol.
Is the same protocol used with all MidNite's charge controllers?

Yes and Yep.

If the ADC has an internal processor, then it would have to be programmed to and interfaced like the WB Jr.

[Barry Fields]

Any reason why the attached would not work?

I have attached the LTspice file.

[boB]

Any reason why the attached would not work?

I have attached the LTspice file.

What is the electrical relationship between the separate shunts and batteries ?

[Barry Fields]

As per your request.

[boB]

Ahhh yes.  Thank you.

Yeah, it would probably work fine for that.  But you can't tell which battery you are looking at since they are all combined into one amplifier.

750 uO is kind of high for the typical home or industrial power battery system but will work of course.

boB

[Barry Fields]

Ahhh yes.  Thank you.

Yeah, it would probably work fine for that.  But you can't tell which battery you are looking at since they are all combined into one amplifier.

I will get to individual monitoring in a minute.

750 uO is kind of high for the typical home or industrial power battery system but will work of course.

I use that because I plan to use 100A/75mv shunts. The circuit should work with with any 4 equal shunts. The divider R14/R15 would be select-able for 50mv vs 75mv shunts.

Before I continue, is there any combination of charge current/SOC/Rconnection that would put U1 at risk? Would different resistor values for U1 preclude that? I would not want a poor connection between the shunt and negative buss to smoke U1.
Thanks for your input.

[boB]

Only thing I can think of that would be bad would be HIGH current that would place the input to U1 too far out of its common mode voltage range.  Any battery current that is normal should be OK.  A lower shunt resistance might help but at the expense of lower resolution on the amps being measured.

You could also raise those 1K Ohms to something higher, maybe 5K Ohms

[Barry Fields]

I have added the 50mv/75mv shunt selector switch and changed the R's to 5k.

Just for conversation I added a couple of 3.1v zenner diode with indicator leds.
Would this further protect the excess common mode excursions?

As far as the voltage drop across the Shunt to neg buss connection, I would expect it to be it's worse on a high discharge current (100A-200A). Would this not cause a high negative voltage on the low side shunt signal.

What voltage might one expect or want to limit during a high discharge?

[Barry Fields]

I apologize for thinking out loud as I post.

I have rethought the LED thing, never mind.

I have included the shunt to buss resistance in the schematic. I reckon all the Rconn's have to be the same or very close.

[Barry Fields]

I have attached a schematic and LTspice for a 555 latching ckt which would latch an overly negative voltage across the shunt to buss connection. It would usually  activate on a large discharge current.
The negative voltage at which it would trigger is up to debate.

I chose R5 & R6 for a trigger around -2 volts. Obviously a lower voltage would be necessary for a 12v system.

V1 duplicates a reset signal for evaluation only. I would suggest a manual reset button.

The circuit would be duplicated for each battery bank. I am not familiar with the quad 558 IC which would probably be usable.

C1 could be labeled LLJ1 (little leyden jar)

[Barry Fields]

As I have not received any "OMG you can't do that" responses, let me proceed.

The prior schematics of the bank combiner, the connection monitor and this configuration would all share the same bank shunts.

Below is attached a method for a monthly evaluation of Bank Health. A total KWH charge data for each bank could be compared and reset monthly.

The performance of the WBjr should not be affected (save not needing its large shunt). It would still deliver total Battery array data and still allow for float current controlled Absorb time (nudge,nudge)