[Ovmsdev] Motor temp does not support negative numbers (car_tmotor)
gipmad at gmail.com
Mon Jan 13 22:20:46 HKT 2014
Håkon, it is industry standard to apply an offset of -40C. We should do
that instead of transforming it to signed, as Collin said. That would also
be directly compatible to the CAN message from the twizy. Let's wait for
2014/1/13 Håkon Markussen <hakon.markussen at gmail.com>
> The highest motor temperature I ever have seen on Think City is ~45 C.
> This is the offset for the cooling thermostat
> I cannot even imagine that other EV-motors should reach a temperature near
> 100C? Then the cooling system have to be out of order ... or ...?
> Anybody who knows the expected operation range of motor temp for Roadster,
> Leaf, iMiEV and Zwizy?
> Think City reports temperature in 8 bits - signed.
> When bit8 (msb) is set to "1" it means negative temperature, so when the
> motor temp actually is -1C , OVMS reports 255C. When motor temp is -11 Ovms
> reports 245C ,etc.
> I think that this problem might apply to all vehicles(?).
> Mark, do you have any suggestion for solution?
> 2014/1/13 Collin Kidder <collink at kkmfg.com>
>> I don't think you'd want to do that. 127 deg C really isn't that terribly
>> hot and -128C is extremely cold. If it is necessary to retain use of an 8
>> bit variable then the standard solution is to just offset the temperature
>> stored by -40. That way you can read -40 to 215C which is a pretty
>> reasonable range. Unfortunately, I fear such a change would necessitate
>> many other changes in code. It might be better to expand to a signed 16 bit
>> On Mon, Jan 13, 2014 at 7:50 AM, Håkon Markussen <
>> hakon.markussen at gmail.com> wrote:
>>> Hi (Mark).
>>> In ovms.h the motor temperature is defined as unsigned char
>>> extern unsigned char car_tmotor; // Tmotor
>>> Currently the weather is cold in Norway (-15 C) and I noticed that motor
>>> temp was 244C.
>>> Is it possible to update the car_tmotor to
>>> extern signed char car_tmotor; // Tmotor
>>> in ovms.h?
>>> Best regards
>>> OvmsDev mailing list
>>> OvmsDev at lists.teslaclub.hk
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