power flow on the ScanGauge II
Is there a way to show the discharge rate of the HV battery on the SGII? I tried the discharge max but it seems to have no relation to the HV battery.
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Re: power flow on the ScanGauge II
Originally Posted by Mark E Smith
(Post 154057)
Is there a way to show the discharge rate of the HV battery on the SGII? I tried the discharge max but it seems to have no relation to the HV battery.
If you take HV battery X HV current, you get what the instrument cluster displays as watts in test mode. The TXD,RXF,RXD are the same whether you want it to display charge or discharge. The difference is in the MTH section. TXD: 0745224915 RXF: 046285490615 RXD: 3010 For correct discharge, MTH: 027108000000 Charging will display a large positive number that is offset by 1999.9. e.g., 20A of charge would display as 1979. For correct charge: MTH: 02710800B1E1 You could program both these, but could only get one to display at a time. The HV current from the TCM is PID 496E and is similar except scaling is different. TXD: 07E122496E RXF: 04628549066E RXD: 3010 For correct discharge, MTH: 027102000000 Charging will display a large positive number that is offset by about 1446. e.g., 20A of charge would display as 1426. For correct charge: MTH: 02710200C781 This is from my memory, so if there are mistakes I will edit the post............ |
Re: power flow on the ScanGauge II
Carl, mine behaves as you describe, and I am getting good at subtracting charge current from 1444 mentally.
I am gong to visit a math professor friend of mine who is also an EE over Xmas. We'll discuss these issues. Also, I have been watching the Max Ch/Dch current statistics. While they do vary based on Battery SOC and temperature, it seems to me the FEH battery does not adhear to them. I think the Max Ch/Dch value is what the generator only is allowed to contribute, and is NOT a HV battery constraint. So if my MAX charge is at 45A for example... cruising, the generator will never contribute more than 45A. However, if I brake hard, the traction motor will contribute up to 70A at this time. Just my observations this week. -John |
Re: power flow on the ScanGauge II
Originally Posted by gpsman1
(Post 154174)
Carl, mine behaves as you describe, and I am getting good at subtracting charge current from 1444 mentally.
I am gong to visit a math professor friend of mine who is also an EE over Xmas. We'll discuss these issues. Also, I have been watching the Max Ch/Dch current statistics. While they do vary based on Battery SOC and temperature, it seems to me the FEH battery does not adhear to them. I think the Max Ch/Dch value is what the generator only is allowed to contribute, and is NOT a HV battery constraint. So if my MAX charge is at 45A for example... cruising, the generator will never contribute more than 45A. However, if I brake hard, the traction motor will contribute up to 70A at this time. Just my observations this week. -John Odd that your professor friend is only an EE over Christmas. I am one year round. |
Re: power flow on the ScanGauge II
Originally Posted by DesertDog
(Post 154191)
Odd that your professor friend is only an EE over Christmas. I am one year round. I'm sure you understand I only visit him over Christmas! |
Re: power flow on the ScanGauge II
Originally Posted by DesertDog
(Post 154191)
Zero MxC happens in my FEH only briefly, but frequently.
I have only seen that once or twice, but I don't have any hills where I'm at in Minnesota, so I hardly ever exceed 53-54% SOC these days. When cold ( 15-25'F ) my MxC is mid-twenties and slowly climbs as the battery warms up. MxD is usually 20 higher ( do we assume amps? ). So when cold ( 25'F ) MxC = 25.0 and MxD = 45.0. When cool ( 45'F ) MxC = 35.0 and MxD = 55.0. When mild ( 65'F ) MxC = 45.0 and MxD = 65.0. I have never seen MxC over 45.0. I don't think I've seen MxD over 69.0. Maybe the scale and/or offset is not correct. When the pack is 65'F and I slam the brake, I get 70A ( a ~1375 reading on the SG for current ) and I think 1445 = zero. -John |
Re: power flow on the ScanGauge II
Has anyone figured out what in the world is going on with these current numbers? It seems like either there is a bug in the SG II, we are using incorrect scaling factors, or something on that order, because these numbers don't make sense to be the result of a binary math error. Unless we should only be looking at 15 bits or 12 bits? If so, that might explain all of the problems.
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Re: power flow on the ScanGauge II
Originally Posted by justindd
(Post 160606)
Has anyone figured out what in the world is going on with these current numbers? It seems like either there is a bug in the SG II, we are using incorrect scaling factors, or something on that order, because these numbers don't make sense to be the result of a binary math error. Unless we should only be looking at 15 bits or 12 bits? If so, that might explain all of the problems.
Reading fewer bits and then adding them back flips the sign and gives wrong values for discharge current. I have tried various other things without success so far. I mentioned this to Ron at Linear Logic in August of 2007 when I was beta testing the xgauges, but he has not had time to look into it due to other pressing concerns. |
Re: power flow on the ScanGauge II
See my post over on the other site:
http://www.cleanmpg.com/forums/showt...?t=5747&page=6 It isn't a limitation of the math on the Scangauge, it is an error in the 2's complement math. Now that I know the error, I have communicated this to Ron so maybe he can fix it. Also, the error factor is really 1999 not 1995. You are absolutely correct regarding the number of bits however, it is definitely 16 bits. I just couldn't see why it turned into 1995 (or 1999) but after playing with it for a couple of hours I finally found the problem. |
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