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My regen was limited for no apparent reason?

Discussion in 'Model S: Battery & Charging' started by Trnsl8r, Feb 3, 2014.

  1. Trnsl8r

    Trnsl8r Blue 85kwh since 12/8/12

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    Hi all,

    Just posting this one rare occurrence that I can't make sense of in case it happened to anyone else. Driving down from the Santa Cruz mountains I suddenly noticed that the yellow dashed line in the regen gauge came up, that indicates regen is limited, at around the 30 kw marker.

    I had done quite a bit of regen on the way down, but not non-stop, there was still some up and down.
    The battery was showing 171 rated miles when I started and just popped up to 174, so it wasn't full by any means.
    The downhill wasn't terribly steep, I don't think I would even have maxed out regen, had it not been limited.
    It wasn't hot or cold out, around mid-40's up in the mountains.
    The marker showed up at least twice, both times briefly, for like 5-10 seconds or so.

    Not a big deal, just curious what made it limited. Any thoughts?

    My car is a fairly early production, VIN 17xx, with an "A-battery", and I am on 5.8.4.
     
  2. Zextraterrestrial

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    upgrade time?
    sounds odd. I just drove over Hwy 17 and back on Pescadero/Alpine(FUN!) last week

    I wonder about the when the regen is not showing limiting but it is obviously limited, this seems just wrong. I never really could get a clear answer about this and why they can't show limiting if the battery can't take the power?
     
  3. Trnsl8r

    Trnsl8r Blue 85kwh since 12/8/12

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    Upgrade what?

    Not sure if you misunderstood me. It did show regen limiting (yellow dashed line on the regen meter).
     
  4. scaesare

    scaesare Active Member

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    What SOC did you start with, and what would you estimate the approximate length of time you were descending the mountains and the average amount of regen power (i.e. 15 minutes of 25kW regen)

    -sc
     
  5. Zextraterrestrial

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    I understood, I haven't ever seen regen come and go like that just peak power when you are pushing it up a hill

    upgrade...battery. I think the B's can take more power in over most SOC. just a guess though, not fact of any sort.
     
  6. mitch672

    mitch672 Active Member

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    Sounds like it could have been the motor/inverter not being able to handle the continuous regen down the mountain for an extended period of time (overheat). Just an educated guess. Everything has it's limits.
     
  7. tom66

    tom66 Member

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    The same amount of heat is dissipated in an inverter/motor in regen for equivalent ordinary power. However, li-ion batteries produce more heat charging than discharging, so the battery could have been getting hot.
     
  8. cinergi

    cinergi Active Member

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    Regen limiter will kick in when it's ~50F outside (and the pack has cooled off enough). And I've seen it appear/disappear/reappear when it's on the edge.
     
  9. Musterion

    Musterion 18h 03m 37s −24° 23′ 12″

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    I commute from the peak of the Santa Cruz mountains in Bay Area into flatland and have witnessed all kinds of spurious regen limiters on the way down, that don't seemed obviously tied to temperature. Over time I have been doing experiments and for sure there is a correlation with getting close to a fully charged battery (100%), as everyone expects. However I am increasing convinced there is a correlation with your particular charge setting. Even on something like 80%, I found when getting close to this target value that regen would be limited, although I would consider this a bug. But for smaller charge settings ~50%, getting close to that set point does not trigger the same regen limit. Of course this is hard to do scientifically since it is done over my days and weeks and the temperature is not a controlled variable. I am on 4.5. By the way, you are missing from the battery wiki table.
     
  10. Merrill

    Merrill Active Member

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    I live on a hill at 900 feet elevation and leaving my house driving to close to elevation I have max regeneration if the temp is above 55 to 60f. Anything around the 50's the dotted line goes around 30 and the last few mornings when it was around 40 the dotted line was at 15. So for me the temp is a factor as to how much regen is available. I usually charge to 175 on my 60. If I leave with the 175 I generally do not get any regen no matter the temp. I have to say it is not always the same, the other day I did a range charge to 201 and when I got in the car to leave I had 198 then when I got down the hill it did go back to 201. It is not very consistent.
     
  11. jchangyy

    jchangyy Member

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    I live near San Jose, Ca., and I have S85. Noted regen limit come up to 30kwh with outside temp around 55F. with 186miles rated several times since I've had the car for a year now. Most of the times, I've had full (normal charge) of 220 miles at 48F without regen limit. Seems random for me. I took it in for annual service and asked them to take a look. I took pictures to show them the discrepancy. service guy started to tell me that regen limit kicks in even without full charge if it's cold, UNTIl, he saw my pics where regen limit kicked in at 55F, and another picture showing no regen limit when car reads 45F. both times, cars have been outside. For the high miles, it was not plugged in over night.(since plugging in with full charge may keep the battery warmed).

    will let you know what they find.
     
  12. Trnsl8r

    Trnsl8r Blue 85kwh since 12/8/12

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    Thanks all. Good tip about the low temperature, did not occur to me. Thought that would kick in at much lower temperatures than 43... Also it did put charge into the battery prior to the limiter appearing. I started at 171 and it just went up to 174 when this happened.
     
  13. Cottonwood

    Cottonwood Roadster#433, Model S#S37

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    The fact that your range had just gone from 171 to 174 means that you had accumulated a total of 1 kW-hr of regen. The MS does not display increased battery capacity from regen until you have accumulated a total of 1 kW-hr; this is either 3 or 4 miles depending on the fractional, non-displayed part of a mile when you started the regen session.

    I have found that there is a short term and longer term regen limit. Several times, I have seen regen limits with a warm battery and 200 miles or so capacity after longer continuous regen sessions. This happens even with a warm battery. When I have compared this to the taper of a Supercharger, it is a comparable limit. My theory is that for small amounts of regen, like slowing down or a short downhill, the battery can absorb more than the Supercharger taper limit. However, for long, continuous regen sessions, the longer-term, Supercharger-taper limit comes to play.

    You probably had a cool battery with enough charge combined with enough regen over a moderate amount of time to hit the longer term regen limit.
     
  14. scaesare

    scaesare Active Member

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    This makes sense. We know from supercharging sessions that the higher the SOC on the pack, the lower the current limit it can accept.

    Just by looking at the graph of voltage & current vs. SOC of my last supercharging session, it appears that by 80% SOC the supercharger was down to 40KW or so... which is well under the kW that regen on the car can provide... so limiting is likely a valid factor.
     
  15. cinergi

    cinergi Active Member

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    When it's 55F the car has to sit outside for a while for regen limits to kick in (since it'll take longer for the battery pack to reach 55). Other factors are involved, too -- like wind which will cool things off faster, or the starting temperature of the pack.
    When was the 45F temperature reading taken? The regen limit has changed in later versions of the software.
    A plugged-in Model S does NOT heat the battery pack (in these temperatures). You'd have to turn the heat on for that to happen.
     
  16. Trnsl8r

    Trnsl8r Blue 85kwh since 12/8/12

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    The car had been sitting unplugged in a parking lot at about 42 degree weather in the shade for a couple of hours before I set off down the mountain.
     
  17. jchangyy

    jchangyy Member

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    45F was the next day. outside.

    Tesla engineers said they found no problems and are blaming the "cold" regen limit as normal. They couldn't reconcile the contradictory temperature and mileage (higher temp showing regen limit while lower temp showing no limit). they said likely software glitch.

    will monitor to see if this phenomena continues and collect all other data (windy, rainy, outside/inside, etc)
     
  18. jchangyy

    jchangyy Member

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    Update to the temperature noted on dash and regen limit. Techs told me that the temperature shown on dash is different from the actual battery temperature--so regen limit is based on actual battery temperature of around 55F. seems bit high to me, but oh well.
     
  19. ecarfan

    ecarfan Well-Known Member

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    I thought the temperature value displayed on the center scene was the outside temperature.
     
  20. PhilBa

    PhilBa Active Member

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    I get regen limiting all the time when the temperature is in the 40s. It's completely normal. I believe that 5.6 or 5.8 is more conservative in this regard.
     

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