[Electric Tire Shredder]

I'm a firm believer that we should not be engaging in self-fixes for this car.

Sorry, no offense, but if you don't want a theoretical self-fix, don't discharge PAST zero, & don't unplug the humidity sensor . Just take it to a dealer where they will almost certainly say nothing's wrong.

Discharging only TO zero has been reported unsuccessful, so you'd want to park by the charger with all the lights on, rear defog, & maybe fan on hi (heater & A/C won't work) for a while, preferably until OBD shows 0.00%, or you get a 12V battery warning: Regain Lost Range for Free!

 

[Electric Tire Shredder]

Thanks, that's kind of nice to know, IF by "distance calculation" you mean what we personally estimated prior to the drive.

However if you mean the GOM most of us ignore for good reason, then it doesn't help as much.

 

[Electric Tire Shredder]

Except that your VW probably does that consistently, much like an eGolf by the way.

The problem with the 500e is that it normally does NOT do that, & then all of a sudden one day you're 28 miles from home with a reasonably-comfortable 30%, & it suddenly drops to an "I won't make it" 22%.

Maybe less stressful if we try to always remember Abe's advice above, so when it does happen, just try to ignore it, because it's just the gauge that's messed up. Then try to recalibrate the gauge with "past zero, then charge non-stop to full". Then it might not do it again for a few years.

 

[Electric Tire Shredder]

What I most found peculiar is discharging like that while Regen braking and stopped at a light

Thanks for the reports.

It's not actually "discharging" *. It's the gauge.

& if a driver doesn't happen to be watching the gauge during the 30 seconds when it drops, they might understandably think (& even report) that it's range loss from battery degradation, even though it's not.

It seems to have happened to me recently too, but I just didn't happen to be looking at the gauge: I needed to drive about 65 miles roundtrip, partly on light-traffic freeway, so I charged to full. Based on nearly 5 years experience with this as my only car, I expected to get back with at least 20% (80% used).

I got home with only "11%" on the gauge (89% used) but it does NOT seem to be from range loss. OBD showed 95% at "full" charge, & 18% when I got home (77% used). Since then I've driven several of my standard 32 mile commutes using 32%, same as always.

So here's a question: It seems like we can recalibrate our % gauges with discharge past zero & non-stop full charge, but if OBD can get a better reading of % charge, why doesn't the display gauge just show that?


* Someone please check my math: 7% discharge in 30 seconds would be about 529 amps, which would almost certainly have destroyed the battery, with lots of smoke & probably fire.

 

[Electric Tire Shredder]

Right. My point is it's "just" the gauge, not actually the battery discharging or losing range.

I'm still wondering why the gauge doesn't show the seemingly-more-accurate OBD %.

 

[Electric Tire Shredder]

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.

 

[Electric Tire Shredder]

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.

 

[Electric Tire Shredder]

How does the battery heater work? Is it separate from the cabin heater

The battery heater heats the antifreeze which flows through the battery pack.

I'm 99% sure the cabin heater is completely separate, heating only the air in the cabin.

 

[Electric Tire Shredder]

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.

 

[Electric Tire Shredder]

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.

 

[Electric Tire Shredder]

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:

0 to 100 percent experiment

So out of curiosity, I've discharged the vehicle to what is 0% on the guess-o-meter and charged it to a 100%. Here are my observations at 0 percent: 1) When you reach 0 percent on the guess-o-meter, the heaters shut off (seat and cabin). Cabin fan and rear window defroster still works. 2) The...

www.fiat500owners.com

 

[Electric Tire Shredder]

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)

 

[Electric Tire Shredder]

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.

 

[Electric Tire Shredder]

SOH values are calculated based on AmpH.

If this is true, it could explain why SOH & AmpH values from OBD are often* so unreliable.

The faster you draw power from a battery, the more energy is wasted as heat, so any battery will supply less AmpH (or kWh) when discharged fast, & more kWh when discharged slow**.

Driving so slow that discharge is very slow, available kWh will increase, possibly even higher than the original specs. That would explain readings of "100%" after tens of thousands of miles. However when "kids" like me are racing "too much" the higher discharge speeds, will make it read unrealistically low.

So I wonder why OBD wouldn't simply measure the capacity while charging, like we now do. At that time the current flow is relatively stable at either 1.4 or 6.6kW (L1 or L2). While driving it can oscillate from 83kW discharge when floored, to 72kW charge on regen.

*Kiesling's may be more reliable if his driving habits consistently match the EPA test.
**A more knowledgeable member may view this as overly-simplistic, but I believe it is at least valid as an analogy.

 

[Electric Tire Shredder]

when it's on zero i need to get it on the mode where the battery comes in and say's only 12V availeble right?

Yes, you need to take the HV battery to 0.00% on OBD, which is reportedly when the motor will no longer propel the car, slightly before the DC-DC cutoff when the 12V battery will suddenly drop from 14.xx v to 12.xx volts on OBD or multimeter. Without either of the latter, you'd have to wait for the 12V batt to drop all the way to 10V for it to activate the warning on the speedo display.

Auxiliaries do not shut off when the HV battery is empty - they keep running.

Reportedly, A/C doesn't actually work after the car's gauge hits 0%, & neither does heat, but the lower-power vent fan works, and rear/mirror defog, low-beams-with-fogs, dome light, hazards, hatch light (& windows & wipers, but I don't recommend those!). Still, as reported above, it can take over 2 hours to go from 0% on the gauge to the required 0.00% on OBD, so driving around a LEVEL PARKING LOT would work, or better yet a sloped one with a charger at the low end.

Alternatively you could get the free AlfaOBD "demo" app & a $19 eBay dongle.

Then you can drive past 0% on the car's gauge, drive around a charger's parking lot until it's near 0.00% on OBD, stop, turn everything that works on, & then plug in after OBD hits 12.xxV.

 

[Electric Tire Shredder]

So it seems like auxiliaries shut down incrementally as the drive battery discharges past 0% on the gauge, taking longer to reach the required 0.00% on OBD. This would tempt me to keep driving until reaching the latter, HOWEVER...:

If the transmission ends up in Park, the parking pawl will be set and you won't be able to push the car.

THANK YOU!!

If you try to save time by driving ALL the way to 0.00% OBD, at your own risk, once you approach that, you can unlatch your seat belt to deactivate auto-park.

 

[Electric Tire Shredder]

Okay, so you went all the way to the 12V warning. Did you then use a metered charger to check the total input kW?

Either way, please let us know if it did in fact correct the sudden drop "from 18% to 0 % in just seconds" that you reported in post #33 above.

 

[Electric Tire Shredder]

No problem. We're here to help

Thanks for the idea about checking total kW input from an app, even if there's no meter on the charger. For example, there's no meter on my local Volta chargers, but their app may show it.

I don't think you can go by an OBD app, since it wouldn't include the EVSE's own power used. The 25kWh EPA spec that we're comparing to is the user's home utility meter reading. OH, WAIT! Now I wonder if metered chargers show their input, or their output! We need input, to compare to EPA's 25kWh input spec.

The difference in total kWh to charge (& your gain in range) should be proportional to what was required to get it from 0% on the gauge to the 12V warning. So I'm curious what you did for that.

 

[Electric Tire Shredder]

No "soft" reset that I know of* BUT the % shown on OBD is reportedly what the motor goes by, stopping only when IT reads 0%**, regardless of what the car's display says. So when it gets low, you could just go by OBD instead of the car's gauge. Last time I checked when my uncalibrated gauge unexpectedly dropped to 11%, OBD showed 18%.

If you do try this, please let us know how it goes.


*OBD text pretty strongly implies its "goal" of 0.00% is required in order to recalibrate SOC.
**Someone (above?) doing a full-discharge recalibration reported that the motor kept running after the GAUGE hit 0%, & didn't stop until OBD hit 0%.

 

[Electric Tire Shredder]

That all makes sense. Also maybe tires being stiffer in cold. I assume you would have mentioned if you were using any heat (cabin or seat). Getting dark earlier can mean more headlight use though.

Less power available from the colder battery shouldn't affect miles/kWh, but would still leave you with less % at the end of the day, since it's effectively like the battery temporarily shrinking.