[Ovmsdev] 12v battery alert threshold?

Greg D. gregd2350 at gmail.com
Sun May 20 07:10:37 HKT 2018

Thanks for the overview, Michael.  I have not experienced the v2 module,
so didn't know how this worked.

If the reference is taken at boot, then plugging the module in with the
car awake would give a too-high value vs when it's asleep.  I guess the
idea is that it should reset itself to a more reasonable value after the
first charging session, yet I'm not seeing that.  It seems to be stuck
at 13v, which presumably was what it recorded at the reboot when I was
playing with the SD card (car was awake and apparently annoyed at the
time).  I'm on the .005 code, which apparently pre-dates Mark's commits,
though the commit was 30-April and the .005 build is dated 1-May...  {shrug}

The algorithm sounds like it is intended to detect a weak battery by
observing its behavior after being charged, but is this sensing
available on all cars?  I'm guessing not, and that the Roadster not one
of them.  For those that aren't, couldn't we just have a configured /
configurable threshold that would trigger the alert?  Regardless of
vehicle type, 12v battery health is an important metric to watch.

Since I'm currently waiting for the modem issue to repeat, I'll just
live with the alerts for now (vs resetting the module to capture a lower
threshold value), and see what happens with the .006 software.  The car
just completed its periodic top-off, generating another pair of events
(12 restored, followed by 12v alert).

Thanks again for the explanation,


Michael Balzer wrote:
> Greg,
> Mark disabled the 12V alerts on the roadster firmware some commits ago.
> Regarding the alert configuration:
> commit 9c1a991a9a27de8afdc9fd408262a2fe0be7aef4
> Author: Michael Balzer <balzer at expeedo.de>
> Date:   Mon Apr 30 22:39:05 2018 +0200
>     Vehicle: 12V battery monitoring & alert
>     New configs:
>     - vehicle [12v.alert] = 1.6       Voltage drop alert threshold in V vs. reference
>     New metrics:
>     - v.b.12v.voltage.ref             12V reference voltage [V]
>     - v.b.12v.voltage.alert           Alert status (bool)
> This works like the old V2 12V monitoring, just a bit improved. The reference voltage is taken after max 15 minutes calmdown time after 12V charging stops. The
> initial reference is the first voltage measured at boot.
> Also, the AD conversion needs to be calibrated for each module, to compensate component tolerances. If you haven't done that for your modules yet, their 12V
> measurements will differ. To calibrate, measure your real 12V level and change config system.adc factor12v accordingly for each module.
> Regards,
> Michael
> Am 19.05.2018 um 02:26 schrieb Greg D.:
>> Hi folks,
>> I'm getting alerts from OVMS that my 12v battery is failing, as it's
>> dropped below the threshold, which is set to 13v for some reason.  So I
>> get a notification every time the car transitions from awake to asleep. 
>> I don't see a configuration item, nor anything in the OVMS v2 app. 
>> Oddly, the threshold is 13.2 for my v3.0 proto module, but I can't find
>> a config item there either.
>> How do I change the threshold? 
>> Greg
>> _______________________________________________
>> OvmsDev mailing list
>> OvmsDev at lists.openvehicles.com
>> http://lists.openvehicles.com/mailman/listinfo/ovmsdev

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