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Chevy volt battery layout question

2061 Views 46 Replies 10 Participants Last post by  piotrsko
Hi there,

I have a full Chevy volt pack that has 7 12 cell 48 v 50 ah batteries plus 2 6 cell I assume 24 , 25 ah batteries.

for my lay out I would like to have a 144 volt setup.

please confirm if this is correct:

3 rows of 48v batteries in parallel making it 144 v total

theN each row makes a series. If I buy a few more I can have 3 12 cell batteries plus 1 6 cell battery in series, making one string. I think this would be 175 amps 50 + 50 + 50 + 25 = 175 amps around 21kw
Can someone confirm if this assumption is correct ? Many thanks
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Don't know where the 3.5V came from. Seems like you're throwing away a lot of usable SoC.
Yabert - published a discharge test - damn NINE years ago

From his test I decided that 4.1v and 3.5 volts were useful numbers - I think I'm only giving away less than 10% - but with the way I abuse the cells I decided that was safer than trying to get the last drop of blood

Rectangle Slope Parallel Font Plot
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You're giving up almost half the capacity by not taking it to 3V.

That said, with wanting every smidge of power on the track, 14% is a lot to lose there.

For the road, I'd take it to the min V, which should be spec'd somewhere (assuming accurate V measurements). 3.5V leaves a lot of energy on the table (read that as carrying double the weight you need to for the range you're utilizing).
You're giving up almost half the capacity by not taking it to 3V.

That said, with wanting every smidge of power on the track, 14% is a lot to lose there.

For the road, I'd take it to the min V, which should be spec'd somewhere (assuming accurate V measurements). 3.5V leaves a lot of energy on the table (read that as carrying double the weight you need to for the range you're utilizing).
IMO & from my personal experience, there's doesn't hardly seem to be anything left/available in a Chevy Volt pack, when the cells get under ~3.5V

FYI: Here is a video with some Chevy Volt Battery testing info (done by USDOE)
...& re-enforces the notion (like I've been saying for years) that the voltage reading can be used as a "fuel guage"

Its ~7 yrs old but, the test results haven't changed
...& he discusses where the info came from
...& also, where to find more, updated data

* Please analize & provide some commentary for us "pal" ;)
Hi there,

I have a full Chevy volt pack that has 7 12 cell 48 v 50 ah batteries plus 2 6 cell I assume 24 , 25 ah batteries.

for my lay out I would like to have a 144 volt setup.

please confirm if this is correct:

3 rows of 48v batteries in parallel making it 144 v total

theN each row makes a series. If I buy a few more I can have 3 12 cell batteries plus 1 6 cell battery in series, making one string. I think this would be 175 amps 50 + 50 + 50 + 25 = 175 amps around 21kw
Can someone confirm if this assumption is correct ? Many thanks
Any tips on tracking down Gen2 96v modules resellers etc THANKS
Sorry - am swamped today, so no time to watch your video.

I was going off the Yabert chart that Duncan relied upon and posted here. There seems to be an energy measurement error just below 3.5V, then it recovers.

That chart shows 7.2mAh (and more) as total usable "energy" (mAh is a component that needs to be combined with Voltage to get energy) capacity by 3V, with only 3.8mAh used by 3.5V.

If you rely on voltage, maybe your system is not capable of using the available power, or it backs off because you set Vmin to 3.5V, but the energy IS there and is unused if you shut down at 3.5V.

You're carrying double the weight, and spending double the money, for only using half or so of the energy available. At the dragstrip, it's arguable that even 3.75V may be worthless.
Sorry - am swamped today, so no time to watch your video.

I was going off the Yabert chart that Duncan relied upon and posted here. There seems to be an energy measurement error just below 3.5V, then it recovers.

That chart shows 7.2mAh (and more) as total usable "energy" (mAh is a component that needs to be combined with Voltage to get energy) capacity by 3V, with only 3.8mAh used by 3.5V.

If you rely on voltage, maybe your system is not capable of using the available power, or it backs off because you set Vmin to 3.5V, but the energy IS there and is unused if you shut down at 3.5V.

You're carrying double the weight, and spending double the money, for only using half or so of the energy available. At the dragstrip, it's arguable that even 3.75V may be worthless.
What happened to the old - "use 80%" rule??
From Yabert's chart 3.5v is 84%
47 Ah total and 39.5 Ah above 3.5v

As far as the carrying excessive batteries bit is concerned - I'm not F1 - I can't select the correct battery pack for the competition

For Drag Racing - I can do a complete days event - and I have used less than half

The same is true for most of the circuit stuff - there was one event - a dubiously legal "faster" event where I had enough for five runs - three for my son and two for me - I decided that an extra run would possibly be too much - one in the last 10 years

On the road the problem is that I have plenty of range for going "local" (50km) - but the nearest big town is 70 km away - so I would need three times my current range
Sorry - am swamped today, so no time to watch your video.
Well, when you get a minute, you should take the time. (y)
It has a lot of interesting OEM Lithium Battery info
...& discusses the results from multiple tests, over several years, done by the US Dept of Energy
...which should be a "book smart" guys dream "credible data" gathered & maintained in a professional format. ;)

* Here's a quick quote for ya, from the video :)

(~4:25) "Here's the Volt discharge curve. It's not flat like Lithium Iron Phosphate, it's linearly decreasing. At rest I can know what the capacity is based off of the Voltage. Which is handy"

If you rely on voltage, maybe your system is not capable of using the available power, or it backs off because you set Vmin to 3.5V, but the energy IS there and is unused if you shut down at 3.5V.
BS
Do you have any "real world knowledge" about Chevy Volt modules?
I do.
I've even produced & posted several videos, of full rides (discharges from "Full ~49V - Low ~41V") on my ElMoto while gathering power meter readings, that clearly showed the Voltage level (steadily) linearly dropping, as the module was being discharged.

I've also, used Chevy Volt modules (& only Volt modules) on several different "vehicles"
...with different set-ups (Freedom Scooter, Land Speeder, Hell-raiser & ElMoto)
...& different systems (24V 500W & 48V 1,000W, 48V 4,000W & 48V 8,000W)
...& the linear Voltage discharge curve, has been consistent on all of them (24V & 48V &/or small motors & also, the bigger motors)
...& as I said, I use the Voltage Meter as the "Fuel Gauge" on all of them (successfully) :cool:

You're carrying double the weight, and spending double the money, for only using half or so of the energy available. At the dragstrip, it's arguable that even 3.75V may be worthless.
You should know better than most anyone, Lithium batteries need a safety margin (especially here in our DIY world)
...& "if" not it can be dangerous (to work with) &/or detrimental (to the health & lifespan of the cells/module)

So then, were back to:
"Establish safe operating parameters (for whatever specific battery chemistry & system you're working with)
...& then, operate within those parameters"
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Most Lithium cells are rated down to about 2.6-2.8V, so 3V is already margined. 3.5 is ~half capacity for all NMC that I know of, so I had no reason to challenge the data in the chart.

Duncan republished a chart he effectively endorsed as a mechanical engineer. Good enough for me - I interpreted the chart and went on with my full day.

You have changed the subject and ignored the chart - you need to point to the data in the chart, and say where it's wrong. Clearly Duncan relied in it, which was good with me given the limited time I had today.
What happened to the old - "use 80%" rule??
From Yabert's chart 3.5v is 84%
47 Ah total and 39.5 Ah above 3.5v

As far as the carrying excessive batteries bit is concerned - I'm not F1 - I can't select the correct battery pack for the competition

For Drag Racing - I can do a complete days event - and I have used less than half

The same is true for most of the circuit stuff - there was one event - a dubiously legal "faster" event where I had enough for five runs - three for my son and two for me - I decided that an extra run would possibly be too much - one in the last 10 years

On the road the problem is that I have plenty of range for going "local" (50km) - but the nearest big town is 70 km away - so I would need three times my current range
The Yabert curve is a voltage vs capacity discharged curve. The numbers of mAh discharged are as I previously posted. Almost half. Lithium chemistries run down to 2.65V as operating spec (for the Bolt EV iirc). So there is margin at 3V already.

The Yabert curve doesn't make sense, though, looking at it now. If it's a ~48Ah cell, which it roughly should be, why does his chart only discharge to 7.x Ah? There's a scale factor missing on the x axis (8x?). It's a hot mess. Shape is right, but the X-axis numbers seem F-d now that I looked at it again.

Where does the 47Ah come from in that curve?

These are times I wish @brian_ would weigh in...
Different chemistries have different voltages - the curve for the Chevy Volt is completely different to the ones for my old Headway cells - they are fully charged at about 3.5v!!

Yarbert's chart shows a steady increase in amp hours removed - until the wires fall off then he starts at zero again

The important bit is where the voltage goes from a nice linear drop and turns the corner THAT is the bit to be avoided!! - and at 3.35v - 3.5v is a sensible "Do not exceed"
Ah...ok. Now I understand what happened.

I read the discharge as 3900mAh, not 39,000mAh, because of the 7200 at the end of the x axis. I didn't process the restart from zero due to the broken wire.

Apologies - Ignore what I wrote. My brain was still at the dry cleaners' this morning.
Most Lithium cells are rated down to about 2.6-2.8V, so 3V is already margined. 3.5 is ~half capacity for all NMC that I know of, so I had no reason to challenge the data in the chart.

Duncan republished a chart he effectively endorsed as a mechanical engineer. Good enough for me - I interpreted the chart and went on with my full day.
I like & respect Duncan
...but, mechanical engineering & electrical engineering are very different fields of expertise
...& as such, those who are educated in either of those specific fields, have different skill sets
&
I like & respect Yabert too
...but, his info was gathered & composed by a DIY'er in a "home setting"

So, I'd at least analyze & compare his data to the USDOE data (which had multiple test subjects & the tests were performed over several years)
...& "if" the data gathered by the (2) different entities co-oberate's, with each other (then, I'd rely on it) ;)

You have changed the subject and ignored the chart - you need to point to the data in the chart, and say where it's wrong.
I pointed out, that my assertion, about the voltage reading of Chevy Volt modules, can be used as a fuel gauge was co-oberated (y)

So, analyzing (simply looking at) the DOE data, under battery specifications it lists:

Vehicle Details
Base Vehicle: 2013 Chevy Volt

Battery Specifications
Manufacturer: LG Chem
Type: Lithium-Ion
Number of Cells: 96
Nominal Cell/System Voltage: 3.7/355.2V
Rated Pack Energy Capacity: 16.5kWh / 45.0Ah
Min/Mav cell voltage: 3.00V -4.15V (I'm pointing to data on the chart) ;)

Now, let's compare that data, to some Real World Data (posted on Aug. 28, 2022)

"Well, my buddy with the 48V golf cart (converted to Chevy Volt Lithium modules 2- 48V 50AH)
...but, somehow, last week he drained them too low.

* I'm not sure if his low voltage cut-off is not set properly
...or if he just forgot & left the system "on" overnight?

When he brought them to me, they looked like this & showing 37.4V (~3.1V per cell)"


* I don't know for sure but, I'd say he initially/accidentally ran them down to probably ~ 2.5V per cell
Here is a link to the original post
Buying used Chevy Volt battery modules/pack questions

Again, I don't want to argue.
...but, I do want to establish actual facts (parameters)
...specifically about these Chevy Volt modules
...so, (I) we can "safely" work within those parameters (facts)
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Anybody have the pin outs for the bms wire
so I can check voltage without removing the black covers ?
(covers are under the buss bars)
thx
This video has info about the pin outs
...& connecting to the BMS plug on a gen 1 Chevy Volt module(s)

A pic of the BMS plug, wire definition at ~7:30 ;)
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Don't know where the 3.5V came from. Seems like you're throwing away a lot of usable SoC.
From being a longtime member of DIYELECTRICCAR
...& personal experience

but the energy IS there and is unused if you shut down at 3.5V.
Not from my experience

you need to point to the data in the chart,
Analizing the DOE data, in the Voltage verses capacity discharged during the static capacity test (at ~4.25) it shows a relatively wide & flat discharge curve, from ~4V down to ~3.3V
...usually ~10Ah incriments
...then, it suddenly DROPS dramatically, from ~3.3V down to ~2.9V (per cell)
...while only spanning ~5Ah (pointing at data on the chart)
&
To, co-oberate, I have experienced this same effect while discharging my Volt modules ;)
Did you read my retraction or are you going to keep responding after I said my posts were rubbish?
Did you read my retraction or are you going to keep responding after I said my posts were rubbish?
Admitting it is Step 1 :p
...Step 2. (maybe) put your "big 'ol brain & vast education" to good use & really analyze the info
...& then, give us (the entire forum) some good-n-accurate info/commentary ;)
Thanks for the compliment, but if it's not what I already know, takes time to figure out or look into, doesn't interest me, or doesn't apply to what I'm doing or plan to do, don't hold your breath on me me taking on your assignments to me.

The Volt is a dead end. The Bolt, Mach-E, Lightning are all interesting, but few, if any, are deciphering them.
Thanks for the compliment, but if it's not what I already know, takes time to figure out or look into, doesn't interest me, or doesn't apply to what I'm doing or plan to do, don't hold your breath on me me taking on your assignments to me.

The Volt is a dead end. The Bolt, Mach-E, Lightning are all interesting, but few, if any, are deciphering them.
Your welcome (y)
...but, theres so MUCH, MUCH more that you need to learn (or confirm) before you go around correcting folks

TBH (so far) I think I've taught you WAY more than you have taught me :p
&
IMO your FOS
...& BS excuses

SMH (shaking my head)

You directly contradicted this info
...& now, you should take the time to correct the mis-information that you have been spreading

This info is very important to the many, many folks that are using these modules
...& also, the forum as a whole (these modules are still asked about weekly)
...& so, we NEED (& would really appreciate) accurate info ;)
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I like & respect Duncan
...but, mechanical engineering & electrical engineering are very different fields of expertise
...& as such, those who are educated in either of those specific fields, have different skill sets
The "relevant skill set" for this conversation is chemistry - NOT electrical engineering

A bit later you reference an actual manufacturers document - that has 3v as a minimum - which is BOLLOCKS

I have been farting about with these types of cells (lithium ion) for about 15 years now and I have discovered that relying on the manufacturers specifications
- as published to us peons - is a very good way of killing your cells
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