PRIME is the third worst in the battery degradation. How is yours holding up?

That article has already been proven very misleading. The method used for data collection was poorly considered... so bad in fact, I have continued my push to document "degradation" in great detail to address such claims.

3 years (close to 46,000 miles now) into ownership, I'm still not seeing any. The same route driven the same way under the same conditions continues to deliver the same results... as this recent video clearly confirms:

 

i do not understand the difference between degradation, range, miles/kwh and charge capacity

 

Sorry, I don't remember details... since I turned focus to data collection instead. I believe the sampling was limited to first year of use, which really doesn't tell you anything. Somewhere in the mix I found a big chunk of the vehicles were fleet use, which doesn't reflect way ordinary consumers would drive. Obviously, that's useful data to fleet purchasers though. So, it does have a somewhat useful nature.

 

Degradation is the disease. Charge capacity is the symptom of that disease. As the battery degrades, it will hold less energy.

Miles/kWh is basically how frugal you are with your right foot. It's a function of the demands on the battery imposed by temperature, terrain, acceleration, deceleration, tire pressure, hvac settings, etc.

Range is the product of capacity and miles/kWh. If the battery has 5 kWh available and you use 5 miles/kWh, your range will be 25 miles.

 

That the Prius Prime would lose battery capacity quickly doesn’t surprise me at all, for two reasons:

First, automotive Li-Ion batteries are only good for around 300-500 full charging cycles. Now that number goes up a lot when you do not charge them fully — from electrochemically 0% to 100% full. That, of course, is why the P.Prime and other EVs maintain 15% or larger charging margins.

Nevertheless, the smaller the battery, the more cycling it’s going to get, for a given amount of EV driving, and the Prime’s battery is among the smallest.

Relatedly, it is only forced-air cooled. Liquid cooling improves battery longevity greatly.

Second, my 2017 Prime has lost quite a bit. It’s currently at 25 miles or so although it has dropped as low as 21, and started at around 35ish. However, that has not been anything close to the gradual decline we would expect of true electrochemical degradation. It drops and goes back up in steps, so I think it’s far more likely that the charging computer is increasing and decreasing the charging margins for fear of losing battery longevity, than that the battery cell are actually electrochemically degrading much (so far).

We need to bear in mind that the Prius Prime was not intended to be used as a pure EV. They intended us to charge it once per day overnight, drive it for a while in EV mode, then automatically switch over to HV when the charge hits the EV/HV threshold. That, as opposed to me, who level-2 charges it two to three times per day! That’s not how they expected nor intended the ‘Prime to be used!

 

That sounds like a good theory. But the numbers on @john1701a's videos alway have always shown an actual SOC of 83% when his car's display shows 100%. Also, the actual SOC when the ICE comes on hasn't changed over the years. If the theory was true, his 2017 would be showing something above 83% actual SOC at the start of his videos and something lower than 13-14% at the end of the EV range. I'l have to check mine to see how it looks.

 

I picked up the OBD Fusion app a while back to see if I can confirm my theory, but I haven’t had a chance to try it yet.

 

I got that one recently, too. I've played with it a little. Takes a lot of time to get the display set up and you have to buy the PIDs for the Prime, but it looks really powerful.

Also, I just discovered how easy it is to do screen recordings on the iPhone.

 

Yup, just a theory. And, if Toyota chose such a short sighted way to mask the degradation, the more the BMS eats into that buffer that's supposed to slow the degradation, the faster the battery will degrade.

If the car was getting into the battery preservation buffer, I'd think by now we'd be seeing complaints of people with high mileage '17s only getting 10-15 miles of EV instead of complaints that they only get the EPA estimate of 25. And again, EV range is totally worthless in comparing one Prime to another and only useful on the same car if you're careful to factor in the many things besides capacity that affect it. My 44k+ mile Prime (not terribly high mileage, admittedly) still takes 6+kWh to charge from 0 EV.

 

Maybe. But Primes make a LOT of use of the battery in HV mode and those partial cycles add up. If the miles are 70 mph miles, then they won't have as much effect on the battery, but at 50 mph in HV mode, mine is in EV at least half the time.

 

Under the right circumstances, those shallow & frequent draws can actually increase longevity. Think of it as stretching before strenuous exercise.

 

My wife got her Prime just 2 months after mine. Driving pattern is different. Her Prime never carries the kayaks or bikes and never goes on the long trips (with 80 mph cruising) to Wyoming either.

Someday, I will film the repeating route with hers. I can't for the next month or two though, since that road is now under construction.

 

I Hadn't thought of it that way. Whatever the case, they seem to be holding up well from what I've experienced and seen. And there's not much I can complain about when getting 60-70 mpg in 40-55mph city HV driving.