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Discussion Starter #1
I have designed & assembled a digital battery pack monitor

A Tri-Quad - 3 meters/displays that provide (4) different readings

It consists of an Amp/Volt meter, to display the total battery pack voltage & the amperage being drawn by the motor (load)
…& also, (2) voltage meters, to display the voltage in each 1/2 of the battery pack

I got the Tri-Quad mounted on the bike & everything connected

Double checked ALL connections before final hook up (plugging the BMS plug in to the battery)

Everything is a "go"

Plugged 'er in
...still looks good

Went to turn the key on to "power up" the system & turn the meters on
…& noticed Balance Monitor Meter #1 is kinda flickering
(how can it do that? they should be off) Weird/NOT GOOD

Then, I turned the key on & everything worked, as designed
...the Amp/Volt meter "lit up" & displayed 45.9V
...the battery balance meter #1 "lit up" & displayed 22.5V
...but, meter #2 didn't do nuthin', nuthin', nuthin'

I went thru everything (3) times
...WTF everything looks "right"

So, (as a test) I got out (2) other Volt meters & connected them in place of the (2) meters that are GLUED IN (what was I thinkin') to the Tri-Quad
…& it seems to work "as designed"

* I think, I burned out balance monitor meter #2

While connecting the wiring harness that goes from the Tri-Quad to the battery pack, I was thinkin'

The Amp/Volt meter is switched on/off thru it's 12V power wires
...but, the (plain) voltage meters are powered, thru the monitor wires, right from the "source"

We gotta add a switch, to be able to turn the meters on/off

So, I added/wired a relay into the "center tap" connection
...I figured that by breaking that single connection, would turn both meters on/off
(This way I could use the bikes 12V system to switch the "higher" voltage stuff (24V - 48V) on/off)


Now, I'm thinkin' that, ...IDK really?

Basically, I had the (2) meters wired in series
...maybe with the "center tap" connection off (disconnected)
...instead of ~22V goin thru each meter, there was the whole "pack voltage" (~45V) goin thru them

They should of been able to handle it
...the specs say DC5.0V - 120.0V (input voltage limit 132.0V)

Here are the ones that I used
Amp/Volt meter
https://www.ebay.com/itm/DC-300V-500...LH_TitleDesc=0

Voltage meters
https://www.ebay.com/itm/122117143903


But, when I look at other voltage meters
...like this one

https://www.ebay.com/itm/Digital-LED....c100005.m1851

I notice, there is no decimal point (like on mine)

The packages are not labeled so, (maybe) did they send me "smaller" meters?
...how could I tell?
 

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Discussion Starter #2
The Amp/Volt meter part of the Tri-Quad works fine
...it was the balance monitor part that had issues

So, I assembled a smaller version of just the balance monitor part
...for testing purposes

This one is wired/connected differently

It uses a DPST switch, connected to each of the outer legs in the diagram
...to turn the meter on & off

Here is a short video describing it in more detail

https://www.youtube.com/watch?v=uzwUiSl0Azg
 

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Discussion Starter #3 (Edited)
It's very easy to connect these voltage meters to a battery pack

For monitoring the "total" pack voltage
...just use (1) meter

Simply, connect the red, positive (+) wire to the battery pack positive (+) terminal
...& connect the black, negative (-) wire to the battery pack negative (-) terminal

or

To set up a Battery Pack Balance Monitor
...use (2) meters

Connect the red, positive (+) wire from meter #1 to (1) pole the "A side" of a DPST switch
...then, connect another piece of red wire, coming from the other pole of the "A side" of the DPST switch, to the battery pack positive (+) terminal

Connect the black, negative (-) wire from meter #1 to the red, positive (+) wire of meter #2
...& then, connect both of them wires, to the "center tap" of the battery pack

Connect the black, negative (-) wire from meter #2 to (1) pole of the "B side" of the DPST switch
...then, connect another piece of black wire, coming from the other pole of the "B side" of the DPST switch

or

To connect a "balance monitor" to a 2kWh section of a Chevy Volt battery pack
...use (2) meters

Connect the red, positive (+) wire from meter #1 to BMS plug pin #8 (brown wire)
...connect the "junction" of the black, negative (-) wire from meter #1 & the red, positive (+) wire from meter #2 to BMS pin #5 (green wire)
...connect the black, negative (-) wire from meter #2 to BMS pin #2 (black/violet stripe wire)
 

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