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Tamás,<br>
<br>
sorry for not being clear: to set the config, you use the command…<br>
<br>
<font face="monospace"><span style="color: rgb(0, 0, 0); font-size:
medium;">config set vehicle bms.log.voltage.interval 1</span></font><br>
<br>
Regards,<br>
Michael<br>
<br>
<br>
<div class="moz-cite-prefix">Am 02.02.21 um 19:02 schrieb Tamás
Kovács:<br>
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<div dir="ltr">Michael</div>
<div>i think the logging enable command is not good : "<span
style="color:rgb(0,0,0);font-family:-webkit-standard;font-size:medium">set
config vehicle bms.log.voltage.interval 1"</span></div>
<div dir="ltr">"To enable logging, set config vehicle
bms.log.voltage.interval to e.g. 1 to check for new
data every second – it will only log the series when
changed."</div>
<div dir="ltr"><br>
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<div dir="ltr">Config and set not swapped? <span
style="color:rgb(0,0,0);font-family:-webkit-standard;font-size:medium">config
set vehicle bms.log.voltage.interval 1</span><br>
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<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">Michael Balzer <<a
href="mailto:dexter@expeedo.de" moz-do-not-send="true">dexter@expeedo.de</a>>
ezt írta (időpont: 2021. febr. 2., K, 17:44):<br>
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0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex">
<div> Everyone,<br>
<br>
TL;DR: I've extended the BMS cell voltage processing to
check for inconsistent / broken series and skip the
deviation analysis and alerts on such.<br>
<br>
After implementing the BMS cell sensor queries for the e-Up
/ Mii / Go, we got lots of cell alerts even on brand new
batteries.<br>
<br>
These were caused by a combination of a) our need to query
each sensor value separately via OBD request, i.e. 84 (or
102 in case of the former model) OBD requests to retrieve
the voltages, and b) the vehicle BMS probably not caring
about taking a synchronized snapshot and holding that before
beginning to overwrite the data with the next measurements.
Or maybe it's actually got some snapshot/hold feature we
just don't know how to use yet.<br>
<br>
Either way, we're seeing the effect of sudden load changes
on the cell voltages clearly within a series run, even
though all 84/102 requests are done within a few
milliseconds.<br>
<br>
Example:<br>
<br>
<img src="cid:part2.3349AC75.ADAE5D9C@expeedo.de" alt=""
class=""><br>
<br>
This is the effect of a low load being present when cells
1-27 were queried, and an increased load being present
afterwards.<br>
<br>
The cell deviation analysis would see a high deviation here
e.g. on cells 15-17 and 75-77 and trigger an alert.<br>
<br>
The green line shows the linear regression gradient. In case
of a series like this, or vice versa (high → low load during
query run), the regression gradient is a clear sign of an
inconsistent series. We also see series like this:<br>
<br>
<img src="cid:part3.65067DA0.6F0C7359@expeedo.de" alt=""
class=""><br>
<br>
In this case, the regression doesn't help. To cover these as
well, I've added a test for a sudden offset in the stddev
level from the previously observed average.<br>
<br>
Note: the average is built as a running average with
smoothing over 5 samples. The first 5 series taken after a
reboot will not be checked for deviations to get an initial
average.<br>
<br>
For both gradient and stddev deviation, thresholds can be
defined. Defaults can be given by the vehicle (added to the
BmsSetCellDefaultThresholdsVoltage() API call), and users
may overwrite these as needed (these may need some more
explanation though). The system defaults I've chosen from my
tests are:<br>
<ul>
<li>Max gradient: 10 mV (= voltage drop/rise over the full
series)</li>
<li>Max stddev deviation: 10 mV<br>
</li>
</ul>
These may be wrong for batteries with drastically different
sensor (pack) layouts.<br>
<br>
I've also reinterpreted the warning & alert thresholds
as "exceeding the stddev level" (used to be absolute
deviations from the average voltage level).<br>
<br>
The max. stddev deviation must not be chosen too low, or
chances are we won't catch faulty cells anymore. If a faulty
cell causes a high change in the standard deviation, it may
cause the series to be considered invalid now. I assume a
faulty cell will not fail completely within a measurement
cycle, but degrade slowly over time. In that case, it should
still be detected.<br>
<br>
I've done some tests with artificial faults and seen some
warnings getting triggered from actual data, so I think the
defaults should work.<br>
<br>
The gradient is published to a new metric
(v.b.p.voltage.grad), which is also shown now in the battery
monitor.<br>
<br>
I've also added a configuration to enable logging the cell
voltages on demand, so you can load your actual data series
into a spreadsheet from a log excerpt. To enable logging,
set config vehicle bms.log.voltage.interval to e.g. 1 to
check for new data every second – it will only log the
series when changed.<br>
<br>
The logging feature is also available for temperatures, but
temperatures are slow movers.<br>
<br>
Please test and report any issues. If you see issues, please
send me your voltage logs for analysis.<br>
<br>
If you haven't had false alerts yet, chances are your BMS
has a synchronized snapshot of the cell voltages. In that
case, you can set the gradient and stddev deviation
thresholds to some high values to effectively disable the
validity check.<br>
<br>
Regards,<br>
Michael<br>
<br>
<pre cols="72">--
Michael Balzer * Helkenberger Weg 9 * D-58256 Ennepetal
Fon 02333 / 833 5735 * Handy 0176 / 206 989 26</pre>
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-- <br>
<div dir="ltr" class="gmail_signature">Üdvözlettel:<br>
Kovács Tamás<br>
<br>
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<pre class="moz-signature" cols="72">--
Michael Balzer * Helkenberger Weg 9 * D-58256 Ennepetal
Fon 02333 / 833 5735 * Handy 0176 / 206 989 26</pre>
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