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Tri-Quad digital battery pack monitor

Functional Artist

Jul 21, 2018
18
Joined
Jul 21, 2018
Messages
18
I have designed & assembled a digital battery pack monitor
...to monitor the 2kWh section of a Chevy Volt lithium battery pack, on my electric motorcycle

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


SAM_1532.JPG SAM_1655.JPG I got the Tri-Quad mounted on to the bike & got everything connected up

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

Everything is a "go"

Plugged the BMS connector in/on the battery
...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
...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"
...so, I 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 (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?
 

kellys_eye

Jun 25, 2010
5,306
Joined
Jun 25, 2010
Messages
5,306
The device you show in:

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

looks to have THREE wires (red, black and white) for the input (3rd and 5th picture where the displays show 120V) - perhaps a separate display power input (max 32V) and the white wire as the measurement input???

Either way, I've ordered various version of those meters in the past and in many cases they sent the wrong model! They've always rectified their errors (since they hate negative feedback) but it pays to test them as stand-alone devices before putting them to use.

I also wouldn't be happy with your switching the 'common' power lead - use a double pole switch and switch them both off simultaneously.
 

Functional Artist

Jul 21, 2018
18
Joined
Jul 21, 2018
Messages
18
Wow!, good "eye" LOL
I didn't even notice the white wire
...both meters (with & without the third wire) are (3) digit LED voltage meters
...but, it looks like the ones for 100V+ don't have the decimal

The meters I have, only have (2) wires (red & black)
...& they only show (2) values, a decimal & (1) more value (up to 99V) I would think?

I agree, severing the common power lead doesn't seem like such a good idea.
…& I did test them first (I'll admit, only on a 24V battery pack)

Here is what the meter(s) do now
SAM_1644.JPG
 

Functional Artist

Jul 21, 2018
18
Joined
Jul 21, 2018
Messages
18
Well, I still have not heard back from that ****** eBay seller

Not one to wait around, I have done some more R&D

The Amp/Volt meter functions of the Tri-Quad seem to work fine. It's the balance monitoring function that "failed"

So, I went ahead & drew up a "new" schematic
SAM_1778.JPG

& assembled just a "Digital Battery Balance Monitor"
...for testing purposesSAM_1722.JPG

& then, tried/tested it on the 45V battery pack, on my motorcycleSAM_1743.JPG

Here is a video with more info, if interested

 
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