Study Ideas - Battery Degradation

Your study should probably account for driving climate, too. All through the winter battery power looked bleak, but with the warmer weather my electric range automatically increased by 2 miles.

 

i think someone said to measure the charge amount from empty. the more it takes, the healthier it is.

 

Mine's empty now and a tiny bit into the hybrid portion. I can let you know what the killawatt meter says after it charges in the morning. Most days, though, I still have a mile or so left when I stable it for the night. But I have no comparison to when it was new.

 

I'm back with my hyper-preliminary report. I had forgotten that my previous charge was not at home, so I couldn't just subtract the previous reading on the killawatt meter. But, in looking over the numbers, I would estimate it typically takes about 3.3 kWh for a full charge. I would have to do two full charges in a row at home (rare) or else take my meter with me to work to be more precise. I'm reluctant to do the latter since my outlet at work is outside and it's been raining every day here in the Sunshine State for the past several days.

 

But what's "empty"? Once EV mode disengages (around 23% SOC) then it's running in hybrid mode, and the ICE starts immediately which changes the SOC again. In a recent long journey I took in 100% hybrid mode, the SOC varied between 18-26%. I just don't think there's an easily achievable point of reference here.

Measuring energy consumption at the mains also needs to take into account loss in efficiency, and differences in efficiency of 100-120V vs. 220-240V charging. A lot of "smart" meters are also woefully inaccurate...

 

it doesn't really matter where empty is, as long as you test it the same way every time. you could start from .1 left on ev, but even if you run it into hybrid mode, long term testing should show any major degradation. hybrid segment of battery is pretty small, and generally maintains between 4 and 6 bars.
but you might be right, i haven't done any testing myself. someone here had their whole charging history graphed out. maybe in the battery degradation thread.

 

Are you referring to post #42 here? Good memory!!
Electric battery degradation | Page 3 | PriusChat

 

yes, thanks! and check post #38 as well.

 

So, it looks like mine is taking a little more than giora's was back then. But then I have more charging overhead since he's in Europe and presumably using 220 volts.

I do want to try some experiments of measuring full charges. I'm convinced that's the most accurate way to measure capacity. It's not perfect because you will have to work really hard using a scangauge or something to have a consistent soc when you begin charging. Using the estimated miles is more a measure of the driver's efficiency skills and the driving conditions. I have no way to know what mine was when new, but at least I'll have a baseline for myself.

 

I have some hard numbers now, but not many. I ran HV down to 0.1 miles and did a charge. Next day, I used it all plus a little and did a charge. Here's a screen shot of my spreadsheet. I showed the formulas in the right column. Does this look like good methodology? I wasn't sure what to use for overhead to account for the difference between what the meter sees and what the battery actually gets. It shows a lot more extrapolated capacity than I expected, but 15% overhead also seems like quite a bit.

 

looks good to me. does the 'overhead' matter, when your just trying to determine long term capacity reduction?

 

Good point. We're just looking for a trend and overhead should remain constant. It would influence the percentage of degradation somewhat, but not the amount in kWh.

Edit to add: I will try to get another reading today to get a broader baseline. I Have been recording meter readings, so I might make another sheet to list and graph them.

 

why don't you post it in your other thread where jerry mildred has been doing yeoman's work on testing.

 

hard to believe mark, how many miles of ev are you averaging?