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Do you think the vast difference in ambient temperatures have anything to do with the soc? I went from leaving in 108 degree heat to 80ish compton to 74 degree Orange County. I would imagine the bms would handle that with all the cooling tech onboard this ain’t a leaf.
My guess is that there's some variable which accounts for some change in the environment (maybe even temperature change over time). I've gotten this when driving uphill at around +8C (46F), just after dark, and I assume a temperature drop. All of a sudden like 10 percent of SOC disappeared within less than a minute.

How does the battery heater work? Is it separate from the cabin heater? Maybe the PID in the system is predicting that the temperature is going to drop further, fires up the battery heating and adapts the guess-the-soc based on the new conditions?
 

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Do you think the vast difference in ambient temperatures have anything to do with the soc?
Absolutely. SOC is not something that can be directly measured. It is a computed estimation based on a number of factors, and temperature is one of the parameters:

 

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Thanks for the link (haven't read it yet though). Meanwhile...:

Those are good theories, & others have reported suddenly seeing the rapid drop when it's really cold.

HOWEVER that may have just been because they went below their normal % (due to the low temp), putting them below the "rapid drop threshold".

Also, when it happened to me I didn't note the temperatures, but there probably wasn't much ambient difference, since I left mid-morning & returned early evening, with no need for heat or A/C even with a passenger who I didn't want to discomfort.

As for "more complicated", it seems SIMPLER to me for the gauge to just use OBD data, instead of generating its own.
 

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2017 Fiat 500e (Billet Argento), 2015 VW Golf Sportwagen TSI 5MT (Tungsten Silver), 2002 Honda VFR
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Here something I found odd today. I went to a public charger and charged from 40% to 80% ok great I left and I parked the car overnight at Girlfriends house it was parked at 77% next day I get into my car it was showing 84% without even plugged in how does that s**t happen? Something really wonky about the gauge on this think I’m gonna have to go by mileage or something more concrete. Oh and bye the way the ChargePoint charged me for 10.31kw so that’s what it took from 40% to 80% so one of the systems lying? Isn’t 10.31kw like 50% charge?
 

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Sounds like you're a prime candidate for % gauge recalibration via discharge PAST zero (to the 12V warning or 0.00% on OBD) & full nonstop recharge.

Charger meters include waste energy, such as onboard charger heat, antifreeze pump(s), battery heat, etc. A post on a recent thread indicates that the battery heater itself often activates when charging.
 

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What I don't get is how a 1000 watt space heater can heat a entire room yet the tiny fiat takes 7000 Watts of power to heat a area size of a typical office cubicle.
 

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The heater uses 7 kW? That seems excessive
Honestly I don’t know for real but it’s been said on many places I’ve read that’s what it uses up so most people just use the heated seats and bundle up.
 

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In a house a 1,500W heater is just warming the cold room air a bit, therefore the delta is small. In a car, the outside temp might be -35F, therefore the delta is very large. Also a car has practically no insulating value, as it is all single pane glass and steel with no insulation. The Fiat 500e PTC heater is 5kW.
108626
 

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The report I saw said 8kW* (bear with me!) initially, to warm the cabin, then 1kW to keep it warm. I think that was on recirculate, at around either 0C or 0F. Yes, I know that's a pretty big temp difference, but either way it's not a constant 8kW or even 5kW.

* It may have been showing 8kW total including the fan, maybe daytime running lights, & maybe brake lights if they had their foot on the brake when testing.
 

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Hello,

My name is Melvin from The Netherlands.
I bought an 500E from the USA and i have the same problem.
I also saw an other topic about this.

We drive the fiat in normal weather conditions and the range went from 18% to 0 % in just seconds.. We drove 80 KMH on cruise control behind a truck .. So not fast.
When he said it was on 0% i recharged it... And after 2.1hours it said 88% full. But i saw in the app it only loaded 14KWH so thats not from 0 to 88%.

Tommorow i go to the local garage to reset the 12v. And talk about this problem. They import a lot of 500E to The Netherlands and maby we can fix this.
I keep you updated :)
 

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12v reset won't likely help.

What does seem to increase available range & reduce gauge drop is to recalibrate the gauge by discharging until the HV battery stops charging the 12V:
  1. Drive until it hits zero near a charger*
  2. Stop & turn everything on*
  3. Wait for a fairly sudden voltage drop at the 12V battery terminals*
  4. Turn it off, plug it in, & charge until it stops*.



*Details:
  1. Ideal charger is 6.6kW or more with a meter, at the low end of a sloped parking lot so you can keep driving below 0% & then coast to it when it dies. Otherwise, when stopped it takes longer to discharge.
  2. Lights on lowbeam/fogs/dome/hazards/brake, rear defog, & fan on high. Nearly nothing else works besides wipers & windows. Maybe crank the stereo & charge your phone. It can take over 2 hours.
  3. It drops from around 14V to around 12V in just a few minutes. You can use a $10 multimeter, or a $20 OBD Bluetooth dongle with the free AlfaOBD "demo" app. Without either of those, you have to wait until it hits 10V for the car's 12V battery warning to appear.
  4. If you want to check your HV battery health, & this is the ONLY known reliable method, use a metered charger, note how many kWh it takes, & divide by 25 to get your % of original capacity.
 

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12v reset won't likely help.

What does seem to increase available range & reduce gauge drop is to recalibrate the gauge by discharging until the HV battery stops charging the 12V:
  1. Drive until it hits zero near a charger*
  2. Stop with the lights on lowbeam/fogs/dome/hazards/brake, rear defog, & fan on high*
  3. Wait for a fairly sudden voltage drop at the 12V battery terminals, from around 14V to around 12V*
  4. Turn it off, plug it in, & charge until it stops*.
*Details:
  1. Ideal charger is 6.6kW or more with a meter, at the low end of a sloped parking lot so you can keep driving below 0% & then coast to it when it dies. Otherwise, when stopped it takes longer to discharge.
  2. Nearly nothing else works besides wipers & windows. Maybe crank the stereo & charge your phone. It can take over 2 hours.
  3. You can use a $10 multimeter, or a $20 OBD Bluetooth dongle with the free AlfaOBD "demo" app. Without either of those, you have to wait until it hits 10V for the car's 12V battery warning to appear.
  4. If you want to check your HV battery health, use a metered charger, note how many kWh it takes, & divide by 25 to get your % of original capacity.
Thank you very much for the time to give me all this information!
I will take this with me when we look to the problem!
 

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Other forum members really deserve the thanks much more than me.

All the real work of actually performing the above & reporting back was done by others who mostly show by scrolling through the replies above, & other related threads, particularly this one:

 

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If it's not too inconvenient, it's best to avoid frequent deep discharge to near 0%. Best to do it only when you need to regain lost range via recalibration.

If you really DO have to frequently go near 0, as you get close, it helps to try to avoid strong acceleration current.

There is also a protective buffer, stopping discharge at 3.1V/cell instead of 3.0
That may not seem like much until you consider that 100% on the gauge is only 4.1V/cell (average of 10% for every 0.1V)
 

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We are some time furder.. I drove the car to 0 and left everything on for more then an hour. It stayed on 0 and did not went to the 12v like what i read in other topics.
I charged the car and the problem seemed to be fixed.
But today i had the same problem again.
I could only charge it to 99% . And when i stoped with charge it went to 100% very strange. I also really think the calibration isnt what is supposed to be.

I went to a local AlfaRomeo garage early this week. They also sell the 500E from USA. And he did some reading of the carr.

All cells were good but there is off course lost of range ( 2014 model 60.000KM ).
There was one code in the OBCM that is reset :
P1503-00 Control Pilot Cyde out of range.

And this is the rest of the information:
Cell Voltage 3967.00 mV ( all the cells the same )
HV Bat SOH 9.804%
HV Bat SOH-C 75.294%
HV Bat SOH-R 35.294%

The mecanic said this was normall for the age and miles.

For me its all new so i am still discovering a lot.
 

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I have 2 major points that I intend as constructive disagreement:

- We've learned that HV Batt SOH numbers are all extremely unreliable, & therefore essentially meaningless. The best example I can think of right now is that unrealistically-low numbers can sometimes suddenly jump back up to an impossible "100%", & vice-versa. "Normal" degradation seems to be about 6% every 26,000 miles (42,000 km).

- All testimony I've seen so far indicates that the % gauge does NOT recalibrate unless you discharge all the way to 0% on OBD, when the motor shuts itself off shortly before DC-DC cuts off (indicated by 12.xx volts on OBD or multimeter). "More than an hour" seems to usually be insufficient. Here's an analogy: Think of being 10km from a light switch. You could walk for "more than an hour" with your arm extended to flip the switch, & the light still won't go on until you go all the way to the end.

When you do that, if you then charge with a metered charger until it stops, check the meter's kWh, & divide by 25 (the US EPA's spec when new), that is the estimate of your current % of original capacity.
 
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