Kev994
Posts: 20
Joined: Wed Aug 28, 2019 6:00 pm
Delivery Date: 14 Sep 2019
Leaf Number: 309727

Re: Rain Sucks

Mon Sep 30, 2019 7:10 pm

I have a TPMS reader, and FWIW it always shows within ~1 psi of my cheap tire pressure gages. I have to tell the reader what car I’m using it on so I suppose the reader could be doing math.
2016 SL Coulis Red

BrockWI
Posts: 795
Joined: Fri Mar 28, 2014 6:28 am
Delivery Date: 28 Mar 2014
Leaf Number: 423875
Location: Green Bay, WI.
Contact: Website

Re: Rain Sucks

Mon Sep 30, 2019 7:18 pm

The TPMS programer I have https://www.amazon.com/Autel-Programmin ... ve&sr=1-12 can also read the temperature of each wheel. I suspect some cars use that as well as a warning, if one of the wheel temps is out of wack from another. It also tells you the battery voltage of the TPMS itself.
3 kw solar pv - XW6048 - eight L16's
4 ton GSHP - 1 ton ASHP
2003 VW TDI 200k miles - 52 mpg lifetime
EVSE level 2 - Clipper Creek HSC-40
2013 S model with QC package Mar of 2013
lost first bar @ 72k
@90k miles - 54.71Ahr - 83.64SOH - 78.44Hx - 237GID

frontrangeleaf
Posts: 46
Joined: Sat Aug 03, 2019 10:07 am
Delivery Date: 08 Jul 2019
Location: Denver Area

Re: Rain Sucks

Mon Sep 30, 2019 8:40 pm

Hmmm. Not following here I’m afraid. I AM at altitude, being in Denver, however.

I can check the car reading again. Car doesn’t report from a standstill, so I have to remember before I drive too far.

Pretty sure standard pressure here is substantially lower than sea level. I know that as a rough rule of thumb one figures 15% less oxygen at 5000 feet above sea level. About 3 % per 1000 feet that is.

It follows that overall pressure would also be lower.

The Leaf is our first car with internal active pressure sensors. All of our other cars monitor indirectly with the ABS wheel speed sensors. Our camper uses external pressure sensors. Both types work well.
Empty-nesters - NW Denver-Boulder Area

2019 Leaf SL Plus
2015 Audi Q5 TDI
2007 BMW Z4 3.0Si
2012 VW GTI

goldbrick
Posts: 617
Joined: Tue Aug 01, 2017 3:33 pm
Delivery Date: 01 Aug 2017
Leaf Number: 311806
Location: Boulder, CO

Re: Rain Sucks

Tue Oct 01, 2019 10:29 am

Do Leaf's use direct pressure measurements? The fact that they only report after being driven for a while would seem to indicate that the sensors use some sort of indirect measurement based on wheel speed, etc.

BrockWI
Posts: 795
Joined: Fri Mar 28, 2014 6:28 am
Delivery Date: 28 Mar 2014
Leaf Number: 423875
Location: Green Bay, WI.
Contact: Website

Re: Rain Sucks

Tue Oct 01, 2019 11:41 am

TPMS are simple and measure the pressure differential between inside the tire and outside at the stem, the temperatur and acceleration. They have a small transmitter that transmits every so often. They "go to sleep" if they don't detect movement after a given time. Acceleration or spinning them is what wakes them up and they start transmitting again.
3 kw solar pv - XW6048 - eight L16's
4 ton GSHP - 1 ton ASHP
2003 VW TDI 200k miles - 52 mpg lifetime
EVSE level 2 - Clipper Creek HSC-40
2013 S model with QC package Mar of 2013
lost first bar @ 72k
@90k miles - 54.71Ahr - 83.64SOH - 78.44Hx - 237GID

GRA
Posts: 11049
Joined: Mon Sep 19, 2011 1:49 pm
Location: East side of San Francisco Bay

Re: Rain Sucks

Tue Oct 01, 2019 6:54 pm

For the curious:
U.S. Standard Atmosphere
Properties of US standard atmosphere* ranging -5000 to 250000 ft altitude
https://www.engineeringtoolbox.com/stan ... d_604.html


*US Standard Atmosphere is the same as International Standard Atmosphere (ISA) up to 32km. Temp and humidity will cause variations from "standard", which is never actually experienced in the real world.
Guy [I have lots of experience designing/selling off-grid AE systems, some using EVs but don't own one. Local trips are by foot, bike and/or rapid transit].

The 'best' is the enemy of 'good enough'. Copper shot, not Silver bullets.

Kev994
Posts: 20
Joined: Wed Aug 28, 2019 6:00 pm
Delivery Date: 14 Sep 2019
Leaf Number: 309727

Re: Rain Sucks

Tue Oct 01, 2019 7:17 pm

GRA wrote:
Tue Oct 01, 2019 6:54 pm
For the curious:
U.S. Standard Atmosphere
Properties of US standard atmosphere* ranging -5000 to 250000 ft altitude
https://www.engineeringtoolbox.com/stan ... d_604.html


*US Standard Atmosphere is the same as International Standard Atmosphere (ISA) up to 32km. Temp and humidity will cause variations from "standard", which is never actually experienced in the real world.
The “standard atmosphere” is just a set of assumptions, it’s useful for keeping airplanes from hitting each other. It doesn’t mean that the pressure is constant from -5000 to 25000 ft.
2016 SL Coulis Red

GRA
Posts: 11049
Joined: Mon Sep 19, 2011 1:49 pm
Location: East side of San Francisco Bay

Re: Rain Sucks

Tue Oct 01, 2019 7:21 pm

Kev994 wrote:
Tue Oct 01, 2019 7:17 pm
GRA wrote:
Tue Oct 01, 2019 6:54 pm
For the curious:
U.S. Standard Atmosphere
Properties of US standard atmosphere* ranging -5000 to 250000 ft altitude
https://www.engineeringtoolbox.com/stan ... d_604.html


*US Standard Atmosphere is the same as International Standard Atmosphere (ISA) up to 32km. Temp and humidity will cause variations from "standard", which is never actually experienced in the real world.
The “standard atmosphere” is just a set of assumptions, it’s useful for keeping airplanes from hitting each other. It doesn’t mean that the pressure is constant from -5000 to 25000 ft.

Yup, an artificial, agreed-upon standard. Now to go dig up my old E-6B computer :D
Guy [I have lots of experience designing/selling off-grid AE systems, some using EVs but don't own one. Local trips are by foot, bike and/or rapid transit].

The 'best' is the enemy of 'good enough'. Copper shot, not Silver bullets.

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