larryh Posted May 31, 2015 at 04:31 PM Report Share Posted May 31, 2015 at 04:31 PM (edited) The following chart is a plot of Voltage vs. ETE for my 60 mile commute from last year and this year. The blue markers are from the commute last year. The red markers are for the commute this past weekend. In both cases, I assumed an internal resistance of 0.12 ohms, otherwise the markers would be spread out much more than they already are. HVB voltage drops with increasing current. I see no significant difference. The BECM can only estimate ETE--it cannot provide an accurate measurement. If the battery were significantly degraded, the red markers should be below the blue ones. I don't know why the BECM suddenly estimated that battery had 7.06 kWh of energy when I started the commute. Normally, it says I only have about 6.85 kWh. I am assuming it changed its mind at the end and corrected the error in the original estimate. Edited May 31, 2015 at 04:33 PM by larryh Hybridbear 1 Quote Link to comment Share on other sites More sharing options...
rbort Posted May 31, 2015 at 05:04 PM Author Report Share Posted May 31, 2015 at 05:04 PM Hey Larry, In both cases, I assumed an internal resistance of 0.12 ohms, otherwise the markers would be spread out much more than they already are. The IR of the battery will change over time and go higher. I'm not sure if you have a way to measure it, some chargers do measure IR and report it with every charge and you can use that to gage how good the battery is and how its changed over time. -=>Raja. Quote Link to comment Share on other sites More sharing options...
larryh Posted May 31, 2015 at 07:08 PM Report Share Posted May 31, 2015 at 07:08 PM I don't know how to measure resistance reliably. There are no PIDs that I see that will help. About the best I can do is the chart above, which doesn't have enough accuracy to detect small changes in degradation. Quote Link to comment Share on other sites More sharing options...
larryh Posted May 31, 2015 at 11:48 PM Report Share Posted May 31, 2015 at 11:48 PM (edited) I'm not sure what to think of the measurements the car is reporting for plug-in energy consumed. For my 60 mile commute this weekend, I recorded the energy consumed and regen'ed to the HVB. The total amount of energy extracted from the HVB was 7.74 kWh. Regen added 1.99 kWh of energy back to the HVB. That's a net 7.74 - 1.99 = 5.75 kWh of plug-in energy consumed from the HVB. During that trip, I recorded the second highest MPGe I have measured for my 60 mile commutes. According to the BECM, the HVB started with 7.074 kWh of energy and ended up with 1.184 kWh of energy (I had about 0.184 kWh of energy left before the ICE would start). That would suggest the HVB provided a net 7.074 - 1.184 = 5.89 kWh of plug-in energy. The car's trip odometer reported the car consumed 5.6 kWh of energy. Last year, the three different computations all matched closely for the commutes I recorded. This year, for some reason, they are all out of sync. I think the BECM is confused. For my commute home today, the recorded power output by the HVB, ETE, and the energy reported by MFM all agreed. I did not note any significant discrepancies. However, this time, the ETE was 6.75 kWh rather than 7.07 at the start of the trip. In addition, the HVB temperature was 73 F rather than 97 F at the beginning of the commute. I probably haven't had enough commutes when I started out with a HVB temperature of 97 F for the BECM to accurately compute ETE for that temperature. Edited May 31, 2015 at 11:49 PM by larryh Hybridbear 1 Quote Link to comment Share on other sites More sharing options...
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