Battery degradation

[LeoNicholson]

We have a 2015 SEL hybrid (39K miles). Was wondering about what to expect for impact upon the traction battery and overall mpg over time. I understand that the car should function for quite awhile, even as the battery degrades.

[plus 3 golfer]

See this thread.  IMO, when looking at the INL voltage vs Ah HVB capacity curves (see first chart below),  I wouldn't expect much, if any, loss in the ability to use the HVB available Ah / kWh capacity in the hybrid HVB over the same range for several 100 k miles. The yellow line is data at 160k miles. Thus, FE should not be affected as the HVB loses "normal" capacity.  If you look at the curves, the bulk of the lost capacity is at the far right of the curve or where the knee of the curve is.  In the operating voltage range of the HVB about 30% to 70% SOC (about 272 V to 295 V), the voltage of the different mileage curves are virtually the same.  In addition, 272V is still rather far away from the knee of the curve.  It would take more degradation to reach the knee where I assume the control algorithms would trigger DTCs and not allow the car to start (failed HVB?).  We also do not know whether the algorithms might adjust the minimum votage upwards to accommodate degradation.

 

I also plotted my HVB data at 103k miles from a test run of 57 miles to see how it compared to the INL data (see second chart below).  My data seems in line with the INL data.

 

 

Edited October 10, 2018 by Plus 3 Golfer

[LeoNicholson]

Many thanks.

Good to know.

I would think this would also apply to the Energi as the larger battery degrades and it operates more as the Hybrid (with 800# of additional weight).

Edited October 11, 2018 by LeoNicholson

[plus 3 golfer]

The Energi HVB has over 5X the energy storage as the Hybrid and the INL data for Energi test vehicles shows around 2X the degradation %.  Lastly, the Energi operates over a SOC % range that is about 2X wider.  Thus, when the Energi loses capacity, the lost capacity reduces the usable energy available for EV now operation and EV range is reduced. 

 

For example, the Energi 7.6 kWh of capacity operates down to about 20% SOC in EV mode. or down to 1.5 kWh. Then, about 40% of the Hybrid 1.4 kWh or about 0.6 kWh would be reserved for Hybrid operation which leaves about 5.5 kWh for EV range: (5.5  = 7.6 - 1.5 - 0.6). The 5.5 kWh is about what most see on their Energi when new.  So, a 10.5% loss in capacity (about a 0.8 kWh loss) would reduce the 5.5 kWh for EV only to 4.7 kWh.  EV only range has dropped about 15%.  If one was getting 25 miles of range, one would now gets about 20 miles of EV. 

Edited October 12, 2018 by Plus 3 Golfer

[ptjones]

From what I have seen with 212k mi. on my CMAX is very little if any loss of MPG's and I think the reason is that normal usage range is between 40-50% SOC so a drop in capacity of HVB would really no effect on MPG's. :)

 

Paul 

[mikekoz]

 We have a 2013 Energi. The battery did great until it was just over a year and a half old. The battery capacity started dropping quickly since then. At first I was able to drive 2500 to 3000 miles between fill ups. My avg MPG was about 246!  It has been dropping like a rock ever since. The car is about 5 years old now, and my MPG is showing as 108. That is not the only reason for the MPG drop on the dash as I do not fully charge it any more on some nights. The big difference is seen on my route to work, which is the same every day. I only get about 10-12 miles now on all battery when I used to get 18-22. Ford says the battery is not defective so they will not replace it. It will be out of warranty after about 4500 more miles so I hope the Energi can run on just gas. We cannot buy another car.

[homestead]

How many total miles do you have on the car?

[mikekoz]

How many total miles do you have on the car?

 

   It has about 65500 miles on it. I think the battery warranty is 7 years, so we actually may have a few more years on it now that I think of it. We bought the car in May of 2014.

[bigqueue]

On 5/17/2019 at 9:25 PM, mikekoz said:

 We have a 2013 Energi. The battery did great until it was just over a year and a half old. The battery capacity started dropping quickly since then. At first I was able to drive 2500 to 3000 miles between fill ups. My avg MPG was about 246!  It has been dropping like a rock ever since. The car is about 5 years old now, and my MPG is showing as 108. That is not the only reason for the MPG drop on the dash as I do not fully charge it any more on some nights. The big difference is seen on my route to work, which is the same every day. I only get about 10-12 miles now on all battery when I used to get 18-22. Ford says the battery is not defective so they will not replace it. It will be out of warranty after about 4500 more miles so I hope the Energi can run on just gas. We cannot buy another car.

 

One thing I have always wondered is whether plug-in car drivers understood the "sweet spot" for their plus in batteries. Lithium Ion batteries don't like a few things....first, they don't like heat. I think the Ford products take care of this, unlike Nissan with the Leaf. (but it really only is an issue if you are in a HOT temperature state)

 

The second thing LION batteries do not like is HIGH State of Charge, or LOW State of Charge. I can see how a plug-in driver could charge their battery to 100% and just leave it there. That is not a great state for a LION battery.....just as discharging it to below 30%....another state it is not happy with. I would think the car software would keep that low voltage condition out of your range of possibilities....but I am not sure if you could run the car in electric only mode and run the battery down that low.....charging to 100% seems totally possible though.

 

I assume your difference in MPG is also seen in the amount of miles you drive on ICE vs Electric...I mean you must obviously see that going way up too....if not, then could it be that the engine has suddenly gotten WAY inefficient for some reason. (just a thought...messed up injectors, etc....)

 

Is there a way to get the car battery controller to spit out each of the cell voltages in the battery pack? It would be interesting to see if there are massive cell imbalances when the battery is charged vs discharged, and/or whether there are some all together "dead" cells. (I doubt that because I think dead cells would actually be dangerous and / or cause a very high cell resistance.....which might well be what is going on....losing power inside the battery itself in cell resistance.