How to test EV battery/warranty

In FL there must be a few HV battery specialists. I'd take to an expert for testing and service. Your warranty is listed in your manual. But I'd prefer using someone who actually knows what they are doing, rather than the dealer.

 

Disconnecting the 12v battery will reset the ECU.

 

The battery degradation is not covered by the warranty. Besides, your number drop does not seem to be out of the normal range. I suspect there is nothing wrong with the traction battery. The EV range on the dash is only a guess. It has very little bearing on the battery's state of health. If you still have the records, check the Eco Diary log on the monthly record, and compare the monthly average miles/kWh for the months when you were getting 25 miles of EV range on the GOM (Guess-O-Meter) vs recent months. I bet your miles/kWh in recent months are down to maybe 3-4miles/kwh or lower.

 

nothing you can do, only warranty is a complete failure. prices are down again, maybe trade up?

 

I don't think resetting ECU by removing the 12v battery reset the number on the GOM. Even if it did, it would not fix anything. As I said, the EV range shown on the GOM is only a guess, and not a very good guess IMHO. Having the number increased to 25 miles by resetting the ECU would not guarantee you that the car will drive 25 miles of distance on the EV mode. The photo below is the GOM number showing 48.4miles on my three-years-old 2017 PP before I traded in last year. The number did not mean much to me since I knew I was only able to drive the car ~18miles on EV mode per full charge at that low temperature of 14F. However, I also knew that the car would drive ~32miles of EV range in the summertime. Still, I could get the number on the GOM to go up if I kept at it up to a max of 50.0 miles. Again, the EV range estimate displayed on the dash of my car had no bearing on the traction battery health, and the number was totally meaningless for estimating the real distance I can drive the car on EV mode.

If you really want to increase the EV range, then you will have to wait for warmer weather and drive more conservatively with slower speed, less acceleration, and less braking.

 

I couldn't believe that statement "Reduction in lithium ion battery capacity is not covered by warranty". So I looked it up and that is exactly what it says in my warranty booklet. Does that mean that if instead of approximately 25 miles I only get 5 or 10 miles that is OK? At what point is it considered a failure of the traction battery? In other words, what is the definition of a failed traction battery?

 

I don’t know of a published definition, beyond what’s in the Warranty & Maintenance Guide. The Toyota Warranty Policy and Procedures Manual for dealers, for example, doesn’t have more specific guidance.

In practice, I imagine most replacements of HV batteries or their stack sub-assemblies—under warranty or otherwise—are done when called for by a Repair Manual (more info) procedure, which would be used after the car’s computers have detected a problem, according to their programming, and stored diagnostic trouble codes (DTCs) such as those for “Cell Circuit Voltage Below Threshold” or “Capacity Decline.” Toyota Techstream diagnostic software also has a Battery Diagnosis utility function, which tests the HV battery and gives a “Normal” or “Replace” result; the latter identifies which stack sub-assemblies to replace.

Toyota hasn’t disclosed specific thresholds for the DTCs or Battery Diagnosis function, however. In the Repair Manual, the phrase “TMC’s intellectual property” is often used, meaning the information has been omitted as a trade secret of Toyota Motor Corporation.

For a rapid and substantial decline in HV battery capacity, even without DTCs or a failed test, one could try to argue—to a dealer, to Toyota, to an arbitrator in the Dispute Settlement Program, or to a court—that this could only have been caused by a defect in material or workmanship that should be covered by the warranty.

 

The batteries (both of them) wear just like tires. And EV range is at the mercy of your right foot. No way could they guarantee that even out the door much less four years down the road. They''d be out of business in no time flat.

You'll see that in your eco page.


You can see above that my 5.8 m/kWh yesterday would have taken me roughly 34-35 miles on my 2017 Prime. A couple day's earlier, my range would have been just over 30 miles. I didn't take a picture, but one day last week I only got 4.5 m/kWh. That would have taken me about 27 miles.

So, to see what's going on with your battery, simply divide the actual EV miles you can drive by the miles per kWh on that day and you'll know the battery's useable capacity. On the rare days that I drive the full EV range before starting the ICE, I usually get 27-32 miles.

Another way to see the capacity is with a Kill A Watt meter. Keep in mind that it will read a little higher than the battery's actual capacity because it's also metering the power used by fans, computers, and heat loss. But that's not very much.

So, @Markelli, if you can show us a picture like the one I just uploaded with similar miles/kWh and you're still only getting 19-20 miles of EV (I do mean "getting" and not predicted.), then we'll know you have significant wear on the battery. But I'm guessing your miles/kWh are closer to 4.0.

 

I feel better having read what Elektroingenieur had to say. At least there is a test and a threshold for traction battery failure. I would not describe the wear "just like tires". I would hope that they would wear just like the engine wears.

 

How often do you charge? Does the battery-pack get many hours to cool prior to charging? What kind of driving is it? If you are flying down the highway at 75 mph with the A/C running, an expectation of 25 miles of EV would never have been realistic. Those conditions are more demanding than what the EPA rating is measured against.

My outcome drops way down when I put demands on it too. It goes up though when I do not. Do you have any type of detailed record of what conditions you had in the past and what you are comparing with now?

 

One test that would help show the difference between gradual deterioration and one or more failed cells would be to run Dr. Prius when the car says that the battery SOC is 0%. If you see many cells that are low it suggests gradual deterioration. If you see just a few low cells with a large voltage difference between them and the other cells it suggests that the lower voltage cells are failing prematurely. I don't know if that info would be helpful when talking to Toyota.

Note that this test requires an OBD2 adapter.

 

Where did that hope come from? It doesn't match up with any battery chemistry or history that I have ever heard of.

My household has kept some cars 17, 23, and 32-and-still-counting years, and they all continue(d) to run well enough to be fully serviceable with MPG similar to new. Dad has farm equipment still on original engines beyond 60 years, certainly quite worn but also still very serviceable. I've never heard of any battery chemistry whose calendar aging function was slow or weak enough to match those engines.

Tires have both shorter distance lives, and shorter calendar lives, than those engines.

 

It was stated that the battery wear is just like tires. Tires last 20 to 50 thousand miles. I would expect an engine to show signs of wear after 150 or 200 thousand miles and I would hope an EV battery would also last that long.

 

Tread depth and traction don't remain constant for the life of the tire, they continually shrink towards zero (at least for tread and wet traction, if not for dry traction). Their also suffer degradation by the calendar when no miles are rolled.

Engine wear is pretty much a function of miles and maintenance diligence, not calendar. Power and MPG don't continually shrink substantially with age, if much at all, until wear is severe.

But batteries very definitely have a calendar element to their capacity shrinkage. My spouse's engine-only daily driver will reach 200k miles shortly, and just passed it 32nd birthday (her commute vanished long ago, greatly reducing its annual miles). Virtually all batteries have shrunk to effectively 0% capacity long before that, due to the calendar element alone, regardless of mileage.

Expecting a traction battery to retain its full original EPA rated capacity, for the life of its hybrid/battery warranty, is just wishful thinking.

 

Exactly. The aging happens in a regular Prius as well as the plugin models. It's just that you can't see it in the regular hybrid until it gets severe enough to affect mpg or power (or throw a code). In a plugin you see it right away as the EV range slowly degrades. This slow reduction in range has been a well-documented fact since EVs first came out.

 

Can we just say they wear like smartphones? It's similar technology though there are obvious differences in construction, scale, charge management etc.

Point is, consumers are familiar with the drop-off in battery performance of their smartphones after a few years- if they've ever kept one long enough, anyway.