Chevy Bolt EV Forum banner

541 - 548 of 548 Posts

·
Registered
Bolt EV, 2019, Premier
Joined
·
11 Posts
I just ran across this thread and I thought I would add my 2 cents to it. I have quite a bit of background designing battery systems.

My best interpretation is that the 57KWh rating on the pack label is a minimum value that LG guarantees. The validity of this number requires additional supporting conditions like temperature, discharge rate and how the battery was charged. Given this, a new battery will always do better. These conditions will only accidently be encountered under actual operation. Now days, these numbers are typically only divulged under NDA. It is a competitive secrete.

Any internally calculated KWh capacity is mainly useful for the DIC. The battery "gas gage" software debits and credits energy (KWh) to some internal reference value as life goes on.
 

·
Registered
Bolt EV, 2019, Premier
Joined
·
11 Posts
Continuing, I believe that the Torque results on capacity are a bit low and should nominally be closer to 60KWh. I like the test of driving at 3.9mi/kwh @ 25C (77F) and seeing how many miles you wind up with. Use that result to calculate your actual KWh capacity.

Actually, just using your actual miles divided by average mi/kwh might be interesting to see.
 

·
Registered
Joined
·
5 Posts
28656


Can someone help me out? I can't get the app to show me the battery's temperature. 2019 Bolt Premier, ELM327 mini
 

·
Registered
Joined
·
4,412 Posts
i also confirm that abnormal cell balance occur while low SOC :
I want to make clear that this wide voltage variation, at very low SOC, is NOT abnormal. It is exactly what you would expect for cells that are not closely matched for capacity. Since batteries in automobiles are top balanced, any variation in cell capacity shows up at the bottom end of charge.

The voltage spread at balanced top of charge is the result of less than ideal battery management circuit design. It reflects the variation in power transistors, and resistors, and doesn't reflect the quality, or capacity of the cells.

I should have made clear that I was joking in my previous post.
 

·
Registered
Joined
·
353 Posts
Can someone help me out? I can't get the app to show me the battery's temperature. 2019 Bolt Premier, ELM327 mini
If the CSV was loaded into any spreadsheet program (e.g. Google Sheets) and then saved, it may have been corrupted, due to some values with an E in them being seen as floating point numbers in scientific notation and being converted to such.
 

·
Registered
Bolt EV, 2019, Premier
Joined
·
11 Posts
Hey ggtronic. Thanks for the battery data! The voltages do tend to diverge some at low soc because the voltage vs capacity remaining is changing very quickly. The curves below assume 3.0 as end of discharge. As you can see, 0.1 volts does not represent much capacity at this low voltage. This is not the Bolt cell but is a similar 48Ah example. Note also that there can be an initial big drop under load at the top end. All of these effects need to be taken into account before getting too concerned about small differences in cell voltage.

28828
 
541 - 548 of 548 Posts
Top