[Ovmsdev] 12v battery alert threshold?

ovmsdev.adelman at adelman.com ovmsdev.adelman at adelman.com
Tue May 22 04:49:54 HKT 2018

> I think this is perfectly normal APS behaviour. The voltage changes
> depending on what parts of the car are switched on/off. I don't
> think we have enough info to alert on APS failure, or even know this may
> be an APS failure based on a simple voltage measurement. My guess has
> been that the different parts of the APS have different output settings,
> and the switchpack may have an involvement as well. It is presumably two
> DC-DC converters in one box (as they can be individually =
> enabled/disabled).

> I=E2=80=99ve never really confirmed 100% what =E2=80=98inhibit APS=E2=80=99=
>  means. I think that it just turns off the part of the APS affecting the =
> PEM (but leaves the car part on - in particular VMS and VDS, and OVMS).

> That 12v battery alert is really intended to alert on little 12v =
> batteries failing. I don=E2=80=99t think it can apply to Roadster based =
> on reading the voltage on the 12v line powering OVMS.

    Perhaps it would be appropriate to change the module's web page
for a Roadster to report "12V bus" rather than "12V battery" voltage.
I was seeing 11.4V and was getting ready to replace my 12V battery
until I (1) calibrated OVMS (187.5 worked for me) and (2) read
further to realize that this wasn't the true battery voltage.


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