[Ovmsdev] Moving to a production cycle

[Greg D.]

Hi Steve,

> The problem is that many EV's don't recharge the 12V battery unless
> the car is turned on.  This dates back at least to the 2002/3 RAV4-EV
> (of which we have one) for which "dead 12V battery" was the most
> common cause of failure to run.

Ah, ok.  I wasn't sure of the general case.  There are videos of folks
using the 12v battery in a Nissan Leaf to run an inverter during a power
outage, with the car automatically topping it off as needed.  My own
Roadster seems to keep the 12v battery at a constant 13.77v, no matter
what the car is doing (on, awake, asleep, charging, etc.).  Never seems
to vary more than 10mv or so, which is really odd, given that the car
should be running off just the 12v battery when it's asleep (it's a
2.0).  I asked about it at my last annual service, and the service
manager (one of the original Roadster techs) couldn't explain it.

A small 12v car battery probably wouldn't mind the 60ma the ovms module
draws by itself.  I don't know what a typical hotspot draws, but if it's
similar, bumping that to just over 200 ma with the SyncUp dongle is
probably too much. 

> If OVMS can be the hotspot, then you don't have to buy and install
> a hotspot.  You would need to choose an appropriate SIM card and plan.

Yes, that's the use case.  I guess I'd rather keep the OVMS module's
processor bandwidth focused on its primary task, and not have odd
traffic trying to run through it to the modem, potentially exposing
otherwise-dormant protocol or timing bugs.  Do we really have all that
much extra CPU power?  Is there a way to throttle the pass-through
traffic in order to keep things stable (or is the modem doing enough of
that for us by virtue of its cellular connection)?

Greg
 

Stephen Casner wrote:
> On Sun, 25 Feb 2018, Greg D. wrote:
>
>> Perhaps yes, but why?
>>
>> If the objective is to eliminate having multiple SIMs and associated
>> payment (a worthy objective!), I think it would be better / safer to put
>> the one SIM in a mobile hotspot, and let everyone (OVMS and other
>> clients) connect to that.  That's what I am testing with the SyncUp
>> OBDII Dongle and the OBD2ECU task, and it seems to work.
> If OVMS can be the hotspot, then you don't have to buy and install
> a hotspot.  You would need to choose an appropriate SIM card and plan.
>
>> The only issue I have is knowing when it is safe to turn off the
>> Dongle's power, and then how to turn it back on again.  I'm not sure
>> it's low enough power to just be on all the time, even given that all /
>> most / some EVs (yes?) have 12v systems that are refreshed automatically
>> from the main (BIG) battery pack.  The ovms module seems to run about
>> 60ma; the SyncUp dongle adds another 150ma on top of that.  How much
>> drain is too much?
> The problem is that many EV's don't recharge the 12V battery unless
> the car is turned on.  This dates back at least to the 2002/3 RAV4-EV
> (of which we have one) for which "dead 12V battery" was the most
> common cause of failure to run.
>
>                                                         -- Steve
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