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Discussion Starter #1
I'm doing pre-buy check of 500e, car has 35k miles, but computer diagnosis saying SOH is extremely low:

  • SOH = 9.8%
  • SOH-R = 58%
  • SOH-C = 72.5%
Is it just computer/calculations glitch? Any ideas?
Owner saying the range is ok and car drives as supposed.
 

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Those look terrible. It could be a glitch, but that's troubling nonetheless. Ask the seller to run it down to zero and charge it back to full again so you can take another reading.
 

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All those readings from any of our OBDs have proven extremely unreliable.

I would take it to my friendly neighborhood metered charger (mine happens to be Greenlots, but I've seen several metered ChargePoints), preferably at low %, & charge till full. Approximate SOH (as a proportion of new) is charger kWh divided by % charged, then divided by 25 (EPA's charger kWh when new). So far, that's the best reading I've been able to find anywhere.

Similar but possibly even less accurate, pre & post-trip % gauge readings, combined with the trip summary that shows at shutdown only momentarily, so have your camera ready, but it shows again on the next full key cycle. kWh used is the miles driven, divided by the mi/kWh reading. Divide that by the % used, & then divide by 21 (approx. new usable kWh).

Those, & any other calculation based on the % gauge, are more accurate after you recalibrate it, as post #2 suggests. However user reports indicate that going "only" to zero on the display seems to do nothing. It seems to be necessary to discharge all the way until the DC/DC converter shuts off, indicated by either the 12V warning on the display, or better to look for a drop from 14.x volts to 12.x volts on OBD, or multimeter on the 12V terminals. Drive to zero near a charger, park at it & turn on all lights & the rear defrost.

Also note that %-gauge-based calculations are more accurate if you measure it from the moment it clicks from one % to the next. For example, record the charger's meter right when the gauge hits say 20%, & if you can't wait for it to go to 100%, record it right when it hits say 85%, so you then know that it put in exactly 65%.
 

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Discussion Starter #4
If I make few FULL change cycles - may AmpH Capacity increase? Currently it's 47 AmpH.
 

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It may or may not increase or decrease, since AmpH from OBD is also extremely unreliable, & therefore pretty much meaningless. I would never trust it, even if it suddenly started reading something reasonable.

If you have access to a metered charger that's the best way to check (detailed above), but even if you don't, you can get a decent reading from the % gauge & trip summary (also detailed above). Either of those is best doing all of the following:

  • % gauge recalibration via discharge to SUB-zero (DC-DC cutoff) followed by non-stop full L2 charge, open/close left door & continue charge til done.
  • Measure over as large a % range as possible. For example charging to full from 10% or even less, or driving from full to 10% or even less.
  • Measure from right when the % gauge changes, so you know it's not mid-way between. This requires a bit of thought though, because when you're driving, the moment it hits 10% it's actually 10.499 & as you charge, the moment it hits 90% it's actually 89.500
  • Do as many tests as practical, preferably several of each, to get a reasonable average &/or ignore any results that are substantially different (mine showed MORE than the original capacity once, on a short trip that wasn't measured exactly from % gauge changes).
 

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What year is the car? Do you know it's history? I assume this car is in Europe? There have been a number of cases where the car was shipped with a low SOC and arrived with a dead HV battery and required extreme measures to recover the pack (disassembly and charging of each individual cell). Li-Ion cells can be damaged if they are completely discharged.
Of course the owner is going to say it it drives fine and range is normal.
Have you driven the car? If the acceleration times are longer than the published values, I would suspect that the pack is indeed not in good condition (high resistance and not able to deliver as much power as a healthy pack).

With a 47 AmpH capacity, the car may appear to have good range if driven conservatively.
To get an idea of what a really healthy pack can do, check out some of Twinturboz posts on this forum. It appears he is able to get close to 100 miles of range driving at freeway speeds (65 mph).
My car is measures around 57.8 AmpH capacity with SOH-R at 99.61%, SOH-C at 89% and SOH at 100%. I can get over 90 miles with mostly freeway driving at 60 to 65 mph and some traffic.
Both cases are at temperatures in the mid 70 degrees F to mid 80 degrees F. Limited or no use of AC.

If you are in Europe, it will not be possible to get the battery replaced under warranty. I suggest proceeding with extreme caution. . .
 

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Thanks Keisling, & I fully agree, with the only exception being the references to SOH numbers from OBD, since they're all extremely unreliable, as actually shown right there with half of the readings being impossible for a used car with thousands of miles (99% & 100%).

Other things to check on OBD that should be more indicative include:
  • Any individual cell voltages being significantly different from the rest, especially after balancing them by charging until it stops.
  • Voltage drop under load. See post #1 at Estimating 500e Battery Health However, like pretty much everything else, it apparently varies by the temperatures of both the air & the batt, & I only recorded the former. I would still check to see if yours is at least close though.
 

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ATM there's no reliable way to check the health status of the battery.

The voltage discrepancies between cells could be a red flag (however, I'm sure PL and UA have shops to deal with that).

However the AmpH or even the SOH percentages are calculated by unknown algorithm and their relevance is unknown. In my case AmpH went up by 0.3 Ah recently, and the GOM range is shooting through the roof.

Charge kWh could be a reliable indicator (25 / actual consumption might be a simplification though). What you have to keep in mind (read PLPs posts in 0-100 percent experiment thread) is that the consumption is dependent on ambient temp - the battery can be additionally heated or cooled while heating, which adds some kWh. Ideally, you should be charging at around +22C (which, again, is also a guesstimate).
 

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Right, it would be nice to know what temp EPA uses. Still, at any non-extreme temp, charging consumption/25 (or driving consumption/21) should at least show that SOH is decent, not really "9.8%".
 

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Discussion Starter #10
Thanks for replies.
Car is 2014, owner measured real range - it's around 87 miles city+highway (not so bad I guess). So I decided to buy it and take all risks.
 

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Please let us know how it goes. Range is VERY dependent on driving style/speed (although there are several other tricks in the recently-updated spreadsheet in the first post here. )

My normal drive is about half 55mph & half slow-&-go* 35mph. It's 32 miles & uses 32%, for a total range of 100 miles.

Yesterday I took the freeway, with ZERO-to-5mph for a few miles, & the rest was 80mph. 23 miles total used 45%, for a total range of only 51 miles!!!

*Lots of stoplights where I can often slow down way in advance to avoid braking below 7mph where regen stops & electric-powered friction-brakes kick in.
 

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Keep track of a couple of your normal drives and calculate the percentage charge used divided by the mileage. THis will give you a realistic way to estimate range. The car's guess gauge is woefully inaccurate. Mine averages 1.6-1.7 percent per mile, and I have been able to use this to routinely and accurately estimate rage remaining.
 

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Right. Personally, I've been getting almost exactly 1% per city mile over the last 15,000 miles.

Stop&go-to-80 was both rare for me AND took my uncalibrated gauge well below 20%, where uncalibrated gauges tend to plummet (adding apparent range loss to the expected real loss at high speed).

The mile gauge IS pretty accurate IF you aren't at either end of a hill (up OR down) or speed change (like city-to-highway, or vice-versa).

Note that an uncalibrated gauge will stop the car from driving when it hits zero, regardless of how much true capacity actually still remains in the battery.
 

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Note that an uncalibrated gauge will stop the car from driving when it hits zero, regardless of how much true capacity actually still remains in the battery.
That was not my experience when I took my car down to zero. I don't remember exactly how far I was able to go, maybe 3+ miles with the gauge at 0%? The limited power mode progressively reduces the available power. I kept driving around my block until the car wouldn't go any more. I would check the OBD SOC values each time I got to my house to see if I dared go for one more lap. The car wouldn't drive anymore when the OBD SOC value got pretty close to zero. I wish I took detailed notes.

I wouldn't bank on it now that I've done it. Having to push the car 75 yards back to my uphill driveway wasn't fun!
 

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Okay, "maybe 3+ miles", but my point is that when the gauge goes out of calibration, the remaining capacity that it's failing to show is unusable, so range drops regardless of battery health. Another forum member gained about 20% range, by going SUB-zero (to DC-DC cutoff) & then 240V non-stop 100% charge.


There may actually be a 1% (3+ miles in turtle mode) "reserve" built into the % gauge, but maybe not...: Consider that it rounds off to the nearest whole number. So as you drive it will show "0%" when it senses 0.4999%, which is good for a few miles at 15mph around the block/parkinglot before it senses 0.000% & stalls.
 

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2017 Fiat 500e (Billet Argento), 2015 VW Golf Sportwagen TSI 5MT (Tungsten Silver), 2002 Honda VFR
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Yes 100miles is easily possible with smooth driving at 65mph (105km/h) and ambient temps above 80f. I could possibly surpass 100 miles if I drafted a truck or van most of that freeway driving I do. I’m happy with with what my Fiat offers for what it is, cheap and fun to drive. So far been totally reliable. Now that I’m going back to work starting Monday it will be piling tons of miles everyday again, 76 miles a day here I come.
 
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