Concerned about Ah decrease in HV battery

  • I'm a little concerned about the health of the HV battery in one of my 451's. I bought it new and I typically do a battery check every six months or so. The Ah number has gone down from 53.1 Ah in 2017 to 45.3 Ah now. I know that Mercedes considers the battery "toast" when it gets down to around 43 Ah or so. So do I have to worry or is there something I can do now to stop the decline? And also, once the Ah hits that magic number, what happens? Is the car still functional? As an FYI, the Ah's in my other two 451's have also gone down, but a bit less - they are in the 47 to 48 Ah range.

    Len

    Len

    2014 EV Coupe 22,000 miles

    2014 EV Cabriolet 23,000 miles

    2015 EV Coupe 21,000 miles

  • I know that Mercedes considers the battery "toast" when it gets down to around 43 Ah or so.

    At 80 %, which is 41,6 Ah, they would replace it for free, if it's still unter warranty.


    once the Ah hits that magic number, what happens?

    Nothing. As it did already, you loose range. But the car drives like before and would do so even if you only had 5 Ah left. Of course not as far anymore as when it was new (100 % battery health are considered to be at 52 Ah). When you got your smart, the battery had about 102 % health. Which is rather normal.


    they are in the 47 to 48 Ah range.

    Which is rather normal. :)


    Feel free to post a full battery check, with all the cells and everything. So it's easier to say something about the battery.

    smart BRABUS #1 in gelb, 04/2023; > 20.000 km

    smart fortwo Coupé 451er ED 3,7 kW-Lader, 05/2013; > 280.000km (bei 250.000 km 22 kW nachgerüstet)

    smart fortwo Cabrio 453er EQ 22 kW-Lader, 04/2021 - 08/2023; 42.000 km

    smart fortwo Coupé 453er EQ 22 kW-Lader, 05/2018 - 05/2021; 109.000km


    "Aus Gaspedal wird Spaßpedal"

    - Smart

  • Thanks for the reply. Interesting to note is that this car with the lowest Ah numbers has the best range of my three 451 EV's by about five miles on average. BTW the car is a 2014 and is not under any kind of warranty. But your 41.6 Ah number makes me feel a little better as does your info that the car will still drive even after it hits that number. :)


    Attached is that latest battery report.


    Len


  • Out of curiosity: Why does it say the cable can do a maximum of 204 A?


    What I'd do now:

    drove the car to < 20 %, charge it up to 100 % and leave it plugged in for another 12 h or so. After that check the "Measurement estimation:" and repeat the process if it's still below 0,8. And check the values again, when the estimat is batter. Right now it's rather terrible, meaning rather imprecise measurements. So therefor the smart is going to say less Ah as it might actually has got. Which would also correspond with the good range you are getting.

    smart BRABUS #1 in gelb, 04/2023; > 20.000 km

    smart fortwo Coupé 451er ED 3,7 kW-Lader, 05/2013; > 280.000km (bei 250.000 km 22 kW nachgerüstet)

    smart fortwo Cabrio 453er EQ 22 kW-Lader, 04/2021 - 08/2023; 42.000 km

    smart fortwo Coupé 453er EQ 22 kW-Lader, 05/2018 - 05/2021; 109.000km


    "Aus Gaspedal wird Spaßpedal"

    - Smart

  • Cable max 204 A? Never looked at that number before. My son built the unit and what cable it refers to I have no idea, but looks like every battery test shows the same thing.


    When you say " repeat the process if it's still below 0,8," what are you referring to as 0.8?


    Len

    Len

    2014 EV Coupe 22,000 miles

    2014 EV Cabriolet 23,000 miles

    2015 EV Coupe 21,000 miles

  • When you say " repeat the process if it's still below 0,8," what are you referring to as 0.8?

    The measurement estimation number.

    smart BRABUS #1 in gelb, 04/2023; > 20.000 km

    smart fortwo Coupé 451er ED 3,7 kW-Lader, 05/2013; > 280.000km (bei 250.000 km 22 kW nachgerüstet)

    smart fortwo Cabrio 453er EQ 22 kW-Lader, 04/2021 - 08/2023; 42.000 km

    smart fortwo Coupé 453er EQ 22 kW-Lader, 05/2018 - 05/2021; 109.000km


    "Aus Gaspedal wird Spaßpedal"

    - Smart

  • Thanks - you know there must be so much information on the HV battery read out that I have no idea what it means. This is the first time I ever paid any attention or even looked at "The measurement estimation number." So what exactly is that number telling me?


    Len

    Len

    2014 EV Coupe 22,000 miles

    2014 EV Cabriolet 23,000 miles

    2015 EV Coupe 21,000 miles

  • We're not quite sure how they are calculated. But from experience we can say that you want about 0,8 if you want a rather precise estimation from the BMS.

    smart BRABUS #1 in gelb, 04/2023; > 20.000 km

    smart fortwo Coupé 451er ED 3,7 kW-Lader, 05/2013; > 280.000km (bei 250.000 km 22 kW nachgerüstet)

    smart fortwo Cabrio 453er EQ 22 kW-Lader, 04/2021 - 08/2023; 42.000 km

    smart fortwo Coupé 453er EQ 22 kW-Lader, 05/2018 - 05/2021; 109.000km


    "Aus Gaspedal wird Spaßpedal"

    - Smart

  • Checked previous reports - battery measurement typically read 0.74 to 0.81. In fact the one in May of this year was 0.81. This car rotates use with one of my other 451 EV's. Each of them typically sits unused for three weeks while I exercise the other one. That other one showed 0.59 on its last test. My third 451 EV is routinely used and doesn't sit for periods like the other two do. It's last test a few days ago read at 0.80. Could the lack of use and down time be a factor I wonder?


    Len

    Len

    2014 EV Coupe 22,000 miles

    2014 EV Cabriolet 23,000 miles

    2015 EV Coupe 21,000 miles

  • While we are talking about this, I had one more 451 EV that I wanted to look at. So I ran the battery diagnostics on it and here is what I found.


    Test 6 months ago:

    Measurement estimation: 0.592

    Actual estimation : 0.462

    CAP mean: 16991 As/10, 47.2 Ah

    CAP min : 17045 As/10, 47.3 Ah

    CAP max : 17368 As/10, 48.2 Ah


    Test today:

    Measurement estimation: 0.805

    Actual estimation : 0.805

    CAP mean: 17392 As/10, 48.3 Ah

    CAP min : 17204 As/10, 47.8 Ah

    CAP max : 17541 As/10, 48.7 Ah


    I like the 0.805 number compared to the last one. Why the difference I have no idea. but I feel better about the condition of the HV battery now.


    Len



    Len

    2014 EV Coupe 22,000 miles

    2014 EV Cabriolet 23,000 miles

    2015 EV Coupe 21,000 miles

  • And here are the numbers prior to charging the car overnight. State of charge was about 25%.


    Last measurement : 24 day(s)

    Measurement estimation: 0.819

    Actual estimation : 0.452

    CAP mean: 17354 As/10, 48.2 Ah

    CAP min : 17239 As/10, 47.9 Ah

    CAP max : 17570 As/10, 48.8 Ah


    Len

    Len

    2014 EV Coupe 22,000 miles

    2014 EV Cabriolet 23,000 miles

    2015 EV Coupe 21,000 miles

  • State of charge was about 25%.

    There it's more interesting what the voltage levels of the cells are. :)

    smart BRABUS #1 in gelb, 04/2023; > 20.000 km

    smart fortwo Coupé 451er ED 3,7 kW-Lader, 05/2013; > 280.000km (bei 250.000 km 22 kW nachgerüstet)

    smart fortwo Cabrio 453er EQ 22 kW-Lader, 04/2021 - 08/2023; 42.000 km

    smart fortwo Coupé 453er EQ 22 kW-Lader, 05/2018 - 05/2021; 109.000km


    "Aus Gaspedal wird Spaßpedal"

    - Smart

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