What is your SOH? Milage? and how do you use your Battery?

[Zprime29]

I hear heat is the enemy. I had a sudden drop after a hot day when the truck was under the sun followed by a short fast charging session (dropped to 98.5% when I was under 10K). It went down to 98% later and came backup to 98.5% where I am now at 16K and 26 months. I didn’t plug in the truck in last two winters. Not sure how much damage cold does.

People say it drops faster at first and then slows down but even if you go down linearly, you will be at 91% SOH at 100K. Not too bad.

SOH is not a useful metric in my opinion, since we don't know how its computed. Linear degradation would mean 94% of capacity at 100k. That to me, is a much more tangible metric.

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[Maxx]

SOH is not a useful metric in my opinion, since we don't know how its computed. Linear degradation would mean 94% of capacity at 100k. That to me, is a much more tangible metric.

That number definitely sounds better. It would be cool to know how they calculate SOH. If they just make a guess based on the number of months, how often battery has gone over and under a certain temp, how often it has gone through high current change and discharge over certain temps, .... or they actually have a way to measure internal resistance of the cells.

Keep in mind the energy presented to ODB-II by BMS is just as much of a guesswork as SOH if not more. My guess is energy is calculated using parameters like SOC (which has been inconsistent and unreliable). Historical data (which can be reset). Current battery temperature and most likely SOH itself as well; since energy has to account for available capacity. So if SOH is unreliable, any calculation using energy is bound to be as unreliable or even more unreliable.

Of course as you mentioned, I don't know any of this for a fact. Anything we read from ODB-II is what Ford is telling us and much of it is calculated not direct measurment. It is all a mater of faith and we can all chose our GODs with little to no proof.

 

[Zprime29]

That number definitely sounds better. It would be cool to know how they calculate SOH. If they just make a guess based on the number of months, how often battery has gone over and under a certain temp, how often it has gone through high current change and discharge over certain temps, .... or they actually have a way to measure internal resistance of the cells.

Keep in mind the energy presented to ODB-II by BMS is just as much of a guesswork as SOH if not more. My guess is energy is calculated using parameters like SOC (which has been inconsistent and unreliable). Historical data (which can be reset). Current battery temperature and most likely SOH itself as well; since energy has to account for available capacity. So if SOH is unreliable, any calculation using energy is bound to be as unreliable or even more unreliable.

Of course as you mentioned, I don't know any of this for a fact. Anything we read from ODB-II is what Ford is telling us and much of it is calculated not direct measurment. It is all a mater of faith and we can all chose our GODs with little to no proof.

I think that's backwards. SoC is based on a combination of voltage and energy spent.

I charged to 100%, giving the BMS a known reference point. Then drove until I hit 14% without charging. I then charged it back to 100%. This gives the BMS a very good estimate of the energy in the pack via coulomb counting. The total energy, I believe is the reference value for determining what % our SoC is.

Maybe @MickeyAO can set us straight on the general concept between SoC and SOH.

 

[Maxx]

I think that's backwards. SoC is based on a combination of voltage and energy spent.

I charged to 100%, giving the BMS a known reference point. Then drove until I hit 14% without charging. I then charged it back to 100%. This gives the BMS a very good estimate of the energy in the pack via coulomb counting. The total energy, I believe is the reference value for determining what % our SoC is.

Maybe @MickeyAO can set us straight on the general concept between SoC and SOH.

On second thought what you are saying about Energy makes sense.

 

[Firn]

I dont believe SOC is based upon capacity. We see a wide variation in calculated capacity for any given temp, if soc was based on capacity we would see less than 100% soc for cold batteries.

I believe that soc is just voltage as I see ~4.09v per cell at 100% soc regardless of temp.

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In other news.

Having just had my high voltage contactor replaced i did notice a change in capacity, previously 100% was a capacity of around 126kwh, now it topped out at 131.07. What was interesting was that it continued to take in a lot of energy even after reaching 131.07, but the capacity didn't change.

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