[Ovmsdev] Roadster cooldown again

Mark Webb-Johnson mark at webb-johnson.net
Fri Aug 23 13:16:09 HKT 2019


I’ve been trying to cool down a roadster, and can’t get it below 30C. I suspect the car behaves differently once that limit is hit, and our cooldown tricks are not as helpful.

Glad for you to help improve the error reporting on this. Let me know if you need anything.

Regards, Mark.

> On 22 Aug 2019, at 4:06 AM, Stephen Casner <casner at acm.org> wrote:
> A week or two ago I ran cooldown on the Roadster with the templimit
> set to 30.  The battery temp was brought down to 31 but not 30, so I
> decided to restore the templimit to the default 31.
> Then today the coolant pump was running again, even though the battery
> was at 52% SOC and cooler ambient temps that the heat spell we were
> having.  So I decided to try cooldown again, but got "Error: Could not
> start cooldown" because the battery temp was already 31.  So maybe
> that default is not low enough even though cooldown may not be able to
> push the temp lower.
> I changed the limit to 30 again and this time cooldown ran
> successfully for 2 minutes to cool the battery to 30 and stop the
> pump.
> I think it would be helpful to have a more specific message than
> "Error: Could not start cooldown".  I see that message is printed in
> the vehicle base code where information about the cause of the error
> is not available.  Would it be reasonable to additionally log a more
> specific message within the vehicle_teslaroadster code to distinguish
> the three possible causes of that error message?  If so, I will add
> that.
>                                                        -- Steve
> On Wed, 31 Jul 2019, Stephen Casner wrote:
>> Mark,
>> Thanks.  I've changed the templimit to 30.  The setting of 25 was
>> probably left over from the testing we were doing last winter.
>>                                                        -- Steve
>> On Wed, 31 Jul 2019, Mark Webb-Johnson wrote:
>>> Steve,
>>> The output looks correct. The car just only turned on the HVAC twice (2 cycles detected) in the hour.
>>> The behaviour of the VMS is pretty much voodoo in this. The cycling of RANGE/PERFORMANCE seems to work once every ten minutes or so for hot packs, but In your case it didn't seem to want to go below 30C. That is average temperature - perhaps the control is more on min/max brick temperature? The conjecture Is that too much / quick cooling would be a bad thing as it would cause condensation within the pack/
>>> Below 31C should be fine to turn off the little coolant pump.
>>> Regards, Mark.
>>>> On 31 Jul 2019, at 5:58 AM, Stephen Casner <casner at acm.org> wrote:
>>>> Today my coolant pump was running continuously even though the charge
>>>> level was only 55% and the ambient temperature was only 77F, although
>>>> the battery was at 89F (32C) left over from a drive last evening.  So,
>>>> I decided to try cooldown again.  The log is below.
>>>> This time the charge current was properly managed at 12A and Range
>>>> mode.  The A/C fans came on soon after starting and the battery temp
>>>> was reduced from 32C to 30C in 3 minutes.  However, after that the
>>>> temperature did not drop further, even though the templimit is
>>>> currently set to 25C, except for a brief period at 29C for 3 minutes
>>>> about halfway through the hour time limit before returning to 30C.  I
>>>> didn't monitor the whole time, but I didn't notice the A/C fans on any
>>>> more.  Does the Roadster not try to cool below 30C?  Yet when we were
>>>> testing last winter while the ambient temperature was cooler, I was
>>>> able to set the templimit to 19C and the car did cool the battery from
>>>> 20C to 19C in the test.  Perhaps the car's goal temperature is based
>>>> on some delta from the ambient temperature.
>>>> This time the session correctly did not turn into a regular charging
>>>> session after the cooldown time limit was reached, and the coolant
>>>> pump did stop running.
>>>>                                                       -- Steve
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