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Mine was also off by about 1000 miles, meaning battery mileage was lower than ODO.
I never found out why...

What is the problem on your screens? I quickly looked and nothing really popped.
 

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Discussion Starter #62
@twinturboz everything looks good to me, especially the Full Amp Hr, which is almost like new (although I'm not sure about the accuracy of it). Try to measure it after a month or so, and see how it behaves.

Mine also had lower battery mileage, compared to the dash.

What was the dash SOC when you took the snapshot?
 

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@twinturboz everything looks good to me, especially the Full Amp Hr, which is almost like new (although I'm not sure about the accuracy of it). Try to measure it after a month or so, and see how it behaves.

Mine also had lower battery mileage, compared to the dash.

What was the dash SOC when you took the snapshot?
My dash was showing 36% and 44 miles remaining.
 

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Mine was also off by about 1000 miles, meaning battery mileage was lower than ODO.
I never found out why...

What is the problem on your screens? I quickly looked and nothing really popped.
Just wanted to see my battery health but information overload in there jeez. It’s like a list of ingredients on a itch cream.
 

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Discussion Starter #65
36% dash, 41% something in the battery management system. I get an impression that the battery management system just doesn't let you go below 5 percent physical SOC.
 

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Unfortunately, so far it seems nobody has discovered any way to check HV batt health.

I started a thread for that where my first new idea didn't work, but my second one might, if only a user or two would simply report the voltage at full charge here.

Most users check the bottom of your first screenshot, for Full AmpH, SOH, SOH-R & SOH-C, but yours is a good example of inaccuracy, since it's obviously impossible to have "100%" health after several thousand miles, & even "99.xx%" is highly unlikely

I like to look at what shows on your 4th pic, where your cell voltages are imbalanced by a reasonable 8mV. I've seen mine grow to around 20, but fully charging brings it back to 6.

...Full Amp Hr, which is almost like new (although I'm not sure about the accuracy of it)...
I'm pretty sure the accuracy is extremely low. User reports here show Full AmpH of 64.9 on a brand new car with only 33 miles, and on one with 34,000 miles after 4 years. Another shows only 44.9 after just 16.5k mi.
 

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I get an impression that the battery management system just doesn't let you go below 5 percent physical SOC.
There is almost certainly a low-end buffer like that, but it seems to me the gauge-vs-OBD difference is just a calibration error on the car's gauge (not OBD showing the % of full capacity).

It definitely doesn't let you go above about 85%. It only charges to 4.1V/cell. That's around 85% of full capacity, but shows "100%" on the car's gauge, & my OBD usually shows around 95-97%

On the low end, I believe "0%" on the gauge is about 2.75V, however I don't yet know what that means in terms of % of true full battery capacity.
 

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Voltage won't tell you the SOH. Voltage under load can give you a better idea. That is why the SOH-R value is important. You can have a crappy battery and it could still show 4.1 volts fully charged. As soon as you put a load on it, the voltage will drop significantly.

When I took my car down to zero (wouldn't move, left the lights and fan on till AlfaOBd said the SOC was zero), the individual cell voltage averaged around 3.1 volts.
 

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THANKS!

Voltage: Right, in general voltage doesn't indicate SOH, but it is related to SOC. The latter was mentioned & my reply to it stands.

HOWEVER, software could allow the max voltage at full charge to gradually increase as the battery ages. That would retain full range for a while, fooling us into thinking we have less degradation than we really do:

Please check this thread & post a reply if/when you can.
 

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I know some electric vehicles do have a way like the Nissan leaf it expands the state of charge in order to look like the same range but I don’t know if the Fiat employs that as I have not seen any other fiats with more than 4.1
 

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Maybe Fiat software fools us by expanding the BOTTOM end:

OBD shows under-voltage warnings start at 2.7V*, leaving quite a bit of capacity below the 3.1V reported by Kiesling as showing at 0%.

Note that 1 volt constitutes 100% of our cars' range, so this extra 0.4V is pretty significant.

Over-voltage warnings start at 4.15V so there's not much capacity to spare there, above the 4.1 we're seeing.

*2.699
 

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How’s it ok to drop volts to 2.7 isn’t that just as harmful as above 4.1? I don’t what’s optimal for a lithium but I’ve seen my secondary Moto Z3 cell phone go from between 2.9v (3%) to 4.4v (100%) Yea I know cell phones are different but they also ain’t thermally controlled either.
 

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Cell phone batteries are very similar physically/chemically, & you're equally well-advised to avoid extremes of SOC or current, but they're much cheaper to replace, even if it means buying a whole new phone.

2.7V might be as harmful as 4.1V. I just relayed the warning activation voltages from OBD. However generally low voltage is apparently less harmful than high voltage. For example, cycling from 10% to 90% is supposedly better than 20-100%. Of course 20-90 is even better.

My point was that even if Fiat isn't fooling us at the top end, they could still be fooling us on the bottom, by gradually lowering the zero % point (where the car stops) from 3.1 to 2.7V, regardless of how much harm that causes, & the subsequent rapid loss of range after that point.
 

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There is a pretty sharp knee in the discharge curve around 3 volts. So going lower than that isn't going to give you much more capacity. I think the 2.7 volt warning is likely used for triggering a flag that something messed up in the BMS or a cell is bad. Pushing 2.7 volts is probably risking damaging the cell.

My guess is Fiat does nothing to trick us one way or another. It is just a compliance car with no warranty on battery capacity or range. I'm sure they just designed the system to minimize the risk of battery damage to increase the chance of reaching the 8 year battery warranty. Limiting the voltage range to ~3.1 to 4.1 volts along with a thermal management system are likely two significant things for reaching this goal. With a small pack, it is what it is. There isn't really room to add an adjustable buffer, protect the battery, and provide a decent range.

It would be interesting to see more data points on average cell voltage at 0% SOC to see if I'm correct.
 
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