[Ovmsdev] 12v battery alert threshold?

Michael Balzer dexter at expeedo.de
Sun May 20 14:44:59 HKT 2018


if a car cannot provide the 12v charging flag it has two options:

a) disable the 12v alert system by overriding the methods (as Mark did)
b) provide a suitable reference value at startup.

Option b can be done by yourself / script:

metric set v.b.12v.voltage.ref 12.65

…or you can raise the threshold from 1.6 to whatever fits your readings.

Maybe I'll add a config for the initial reference voltage on startup, as that can also be wrong due to 12v noise.


Am 20.05.2018 um 01:10 schrieb Greg D.:
> 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,
> Greg
> 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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