Darkflow wrote:

OK, so latest update over at youtube unplugged EV is that the BMU calculates SOH by applying just two fixed degradation factors:

-0.3% for every month

-1.0% for every 6200 Ah in/out of the battery.

That's if the BMU is set to think that the starting battery capacity is 38 Ah.

Mine is, and that calculation closely matches my current BMU reported SOH.

Apparently someone has been looking directly at the BMU code, which is not sophisticated.

Now I have already replied to some of this post above about it being old news from my previous research but I will now discuss the so called % values that is mentioned here.

It appears to me they are trying to get formulas to match the values for the Secular (calendar or age) and cycle deterioration as shown on the MUT-III reports.

Now I have at least 3 of those MUT-III reports (that I can find at the moment) for my oldest PHEV which I still own.

From what I can see from my quick appraisal of those reports those values are not always lining up with what I am seeing. For example:

1st report with BMU data list number 396 of 35 months I should see according to their so called 0.3% for every month formulae 10.5 %. Secular (calendar or age) deterioration on my report is 12.83% (.273%/month)

2nd report is showing 47 months with Secular (calendar or age) deterioration of 14.55% (.309%/month) their formulae 14.1% Ok closer

3rd report is showing 59 months with Secular (calendar or age) deterioration of 16.06% (.272%/month) their formulae 17.7%

Now lets get to the cycle (or Cyclic) deterioration and their 1.0% for every 6200 Ah in/out of the battery formulae.

1st report in the same order as above Charge and Discharge intergrated current 47,652 Ah actual report 9.25% their formulae 7.69%

2nd report Charge and Discharge intergrated current 65012 Ah actual report 10.76% their formulae 10.48%

3rd report Charge and Discharge intergrated current 75332 Ah actual report 11.89% their formulae 12.15%

Not sure I trust their formulas so far.

though they got close a couple times I suppose.

Now as for adding those values together to get the so called BMU reported degradation of our batteries lets see what we get.

Now none of these reports have a BMU recalibration (or "Auto Capacity Measured Procedure") done to them so it will not screw up the measurement.

1st report Battery current capacity 100-(32.7 Ah/40 Ah) x 100 gives 18.25% add their formulas together 18.19%. Ok this is close.

1st report Battery current capacity 100-(32.7 Ah/38 Ah) x 100 gives 13.95% add their formulas together 18.19%. Not so close as seen by the apps.

2nd report Battery current capacity 100-(29.9 Ah/40 Ah) x 100 gives 25.25% add their formulas together 24.9%. Ok close again.

2nd report Battery current capacity 100-(29.9 Ah/38 Ah) x 100 gives 21.32% add their formulas together 24.9%. Not so close as seen by the apps.

3rd report Battery current capacity 100-(26.8 Ah/40 Ah) x 100 gives 33.00% add their formulas together 29.85%. Not so close.

3rd report Battery current capacity 100-(26.8 Ah/38 Ah) x 100 gives 29.47% add their formulas together 29.85%. Close as seen by the apps.

So all in all IMHO it is ok in some parts but it has very mixed results for "apparently someone has been looking directly at the BMU code".

I think that so called person might be having us on and is just guessing or "winging it" probably using just one report IMHO.

But I will check those calcs later to make sure I have entered them correctly as I was in a hurry.