Another Battery Degradation Thread

Soon it will be out turn to frigid digits.................

 

It's 0 out now, and after those temperatures I've got a t-shirt and jeans on. Going skiing this weekend, 20+ inches of powder at some of the resorts.

 

Marvelous......

 

Sure you got the powder alert!
Have fun!
Yeah low tonight 1 degree f. here also!

 

the only powder i'll be seeing is on my donut.

 

Yesterday provided new & unexpected data. Clearly, Toyota has a well thought out system.

I went out to plug the Prius, late in the afternoon after having sat outside all day while I was working. The temperature was 19°F outside. I had expected the temperature of the battery-pack to have fallen to below freezing. After all, it showed itself to warm up from outside influence during the Summer. Turns out though, cold apparently has less of an effect. The temperature of the battery-pack was actually 51°F. That's great news for Winter operation. It also explains why EV is so easy, even when very cold out.

That made me quite curious what it would be when I left work 2 hours later, after having fully recharged. To my surprise, it had only risen to 54°F. Though the outside temperature had dropped to 14°F, I still expected the act of drawing electricity to result in more heat.

Later, when cold season eventually takes an icy grip on us and highs stay below 0°F, that should be especially intriguing.

 

It was 14-19F outside but what was the temperature inside the car? This was daytime, I think. Was the car shaded by a roof overhead or was the car out in the Sun with the windows shut? Was the rear hatchback cover shading the hatchback floor from the Sun?

The good news in the winter is that the Prius battery is somewhat exposed to cabin temperatures and solar load which may help keep it warm during the day. Of course, that also exposes it to potential heat during the summer and may lead to more rapid temperature drops in shaded areas with cold outside temperatures or in the evening in the dark.

Some other cars like the Volt have the battery fairly isolated from the cabin. The Volt battery is also additionally insulated and is centered in the vehicle where it is surrounded by lots of vehicle structural mass that is slow to change towards ambiant temperature under all conditions without using its active liquid thermal system.

 

why would you post this in the pip forum?

 

I wondered how the PIP battery was affected by extreme heat or cold because it is not well insulated. I've measured battery temps while driving my old 2012 Three and they can change fairly quickly. Parking in a sunny location during the winter may be advantageous to the PIP battery as it is to the driver.

 

Did you mean "stay below 0 centigrade " ?

 

When temperatures here started to drop below freezing and my EV range also started dropping to around 11 or 12 mi I experimented using a ceramic heater behind the drivers seat to warm the air near the floor battery air intake while charging. But while driving even though the cabin was much warmer than outside temps I could feel the wind chill cooling the floor under my feet and I couldn't get any more EV range than if I had not used the ceramic heater to warm the cabin.
Temps warmed to near 70 F again last week during the day and my EV estimates and range again climbed to the mid 14's but are slowly dropping again with outside temps back into the low 13 mi range.
I'm sure most of this is old hat for you guys that winter EV experience, but it's all new to me.

 

Those of you from down south seem to forget how sharp the angle of the sun is and how short the day is here in the north.

There is very, very little radiant heat available until Spring. How you park basically makes no difference for Sun influence.

No! I mean proper cold. 0°F, which is -18°C

 

Don't worry, I am quite sure that MN is too cold for my tastes.
My 'hood has about 1200 HDD in January. Quite cold enough, thank you.

Out of curiosity though I looked up weather data for Minneapolis. Median HHD for January is about 1600 starting from 65F which means average 24 hour temps are about 10 - 15F. This about matches this graph, grabbed from a NOAA website. An area that routinely stayed below 0F would have around 2000 HDD in a month. Fairbanks AK averages 2400 HDD in January and reached 3000 one year. I feel cold just reading about it.

 

We have been having a cold snap here in So Cal and my range estimate has dropped from 10.1 to 9.7. Today I had a chance to drive in light traffic with less stoplights. Temp was 57 F and my actual was 11.3 miles before the car switched to HEV. Still I do think I am gradually loosing capacity.

 

agreed. i think i've lost about 10%, but the initial loss is supposed to be the biggest, and then it slows down.

 

How many miles do you have on your PiP?

The INL has been testing various plugin cars for battery degradation among other things.

Advanced Vehicle Testing Activity - Plug-in Hybrid Electric Vehicles/Extended Range Electric Vehicles

They have several 2013 PiPs with 20-40k miles that are showing 3-5% battery capacity loss (relative to a base capacity measured with 4-5k miles on the car). Their Volts show similar if slightly better results.

The results are slight enough that many owners with less than 50,000 miles should have difficulty noticing any change by casual observation, especially with simultaneous tire wear leading to lower rolling resistance.

Volt owners may see less degradation than is present in the actual battery because the Volt partially compensates by mildly increasing its usable SOC window over time, according to GM electrification engineering executive Larry Nitz who confirmed this to me at the recent private Volt show-and-tell in Los Angeles.

 

An initial drop in battery capacity in the first days of driving is expected. IIRC it is 5-10%, then the capacity plateaus for a long time (hopefully.)

 

i have 18,000 ev, 8,000 hv. of course, nothing scientific, but my commute is exactly the same 14.4 miles every day. the only variable is the weather. the first summer, i could drive to work and back with 1 0r 2 miles left. now, i can just barely make it, or i have to drive a little slower.

 

It's a shame they're mostly doing mixed mode. In terms of energy storage, the ~19k+ miles the first VIN did in mixed mode is only equivalent to ~2k+ miles in EV.