L2 daily charging: restrict to 8A for battery health?

Mirrors my experience this winter so far (first winter).

 

What are the results you might get, other than saving a buck-and-a-half during the entire winter months?
EV Li-ion packs have a TMS for a reason.
I wonder why toyota made this heater selectable?
(-26F is a windchill, correct? Not the same as ambient temp for a piece of metal parked outside.)

I think I read some EV's 'brick' when NOT plugged in, and do not allow the HV pack to come online below ~ -25°F.
All you get when powering it up is a msg. "Plug in to warm the pack" or such....

But with the PP all it has to do is spin the engine enough to ignite the smell maker.
I wonder if then the HV pack heater self engages, regardless what the (frugal?) owner selected somewhere in the settings.

 

Twice in the past few days, with a full battery, the engine started up right away (HVAC was off in each case). First time, ambient temperature was -20C (about -4F). Made sense. Second time, temp was -9C (~ +16F). Made less sense (to me). I park outside, so properly cold each time. Also, each time the energy flow indicator showed a flow of energy TO the battery on the short drives taken.

My best guess:

Case 1–no way to prevent engine from coming on owing to temperature conditions. Energy flow to the battery was attempting to warm it up rather than actually charge it.

Case 2–same as Case 1. The difference being that after my short drive to the grocery store, during which the energy flow was identical to Case 1, my return trip (even with HVAC on, but not front defroster) remained entirely in EV-only mode. I strongly suspect the initial drive to the store had sufficiently warmed the battery so there was no need (from the system’s point of view) to activate the engine again.

 

For all I know, the traction battery heater function on the PP is not a part of TMS ordinarily thought of for BEVs. As a simple reason, this Traction battery heater function is an operator selectable option. The car may come with the option turned OFF and a user may never know to turn it ON. Also, there is no mention in the manual to keep the car plugged in during the cold nights. Similarly, PP is equipped with the traction battery cooler function. This function is even less important, and definitely not a part of TMS, as it is set OFF by default, and it takes great effort to turn it on by the operator. I suspect many PRIME owners don't even know how to turn this ON.

As I stated before if the low temp damages the Li-ion traction battery in PP without battery heater function and requires the charging cord plugged in, then how the heck all Gen4 Prius hybrid with the same Li-ion chemistry battery pack manage to keep turning on and charge on HV mode during an extreme cold?

BTW, -26F was not windchill. It was forecasted temp, but it did not pun out. The actual official low temp of the day was -16F. But the wind chill was something like -50F two nights ago. At my home location, the lowest outside temp was -14.0F, the lowest temp inside of the car (front dash) was -11.7F, and the lowest temp inside of the traction battery compartment was -6.3F. Those temperatures were measured by separate BlueTooth temperature/humidity probes positioned at the locations stated. The traction battery was fully charged more than 12 hours prior to the low temp and the car was not plugged in during this measurement, yet somehow the traction battery compartment stayed almost 8F warmer than the outside temperature or 5.4F warmer than the cabin temperature. This means the traction battery compartment is greatly insulated than the car itself and/or there is TMS to warm up the battery pack even when the car is not plugged-in.

 

Functions that warm or cool the HV battery pack are TMS.
No matter how convoluted a manufacturer makes it.
But carry on.

A black PP in Tucson charging in the sun should benefit from having the cabin AC gently wafting cooler air through the HV battery pack.
A PP in the Great White North should benefit from using the built in pack heaters, one would think...
Why have them otherwise? Strange that in requires the owner's involvement

I guess if the Gen4 prius has the same chemistry in the cells (same cells, but less of them?) it can handle whatever weather conditions the car encounters.

 

Yep, that's the greatest mystery I want to solve by experimenting with them. At least with a small number of experimental use cases I have done, it is fairly clear that they are not required for normal operation. Just like for the Gen4 Prius, PP's traction battery can handle whatever weather conditions the car encounters without a traction battery heater and traction battery cooler.

For the longevity of the traction battery may be the reason Toyota included those functions. But it is so strange if that is the case, then why don't they make it a requirement or at least state in the manual to recommend to use them. Toyota makes a great deal recommending using a charge schedule to minimize the time the traction battery spends fully charged in order to prolong the life of the traction battery, but never mention the use of the traction heater or cooler for that purpose. It is possible that those functions were just value-added features without any data supporting they do any benefit. Yeah, the rationale for using them is "It's not going to hurt using them and costs only a few pennies, so just turn it on and keep it on."

For one thing, I know the PP manual does warn of the lower limit of operating temperature for the hybrid system. The manual states -22°F (-30°C) for this limit. Yet, even for this warning, it makes no recommendation to plug the car back into the wall to use the "Traction Battery Heater". It just says wait for the outside temperature increase etc... Yay, for those who are living in Alaska or Northern Canada, that must mean wait till Spring thaw. LOL

Fortunately, I have not yet encountered a situation my PP does not start due to cold temperature. I think for the battery pack to reach -22°F (-30°C) or below, it must be exposed to the continuous ambient temp of -22°F (-30C) or below for prolonged time like weeks. Our local average temperature of the coldest month (January) is 21° / 2° High / Low(°F). So, -22°F is rare. And even if it happens, it is usually not for prolonged periods, so the traction battery has very little chance to get that cold.

 

1. Yep, strange, that's why TMS is there, and also for charging performance in cold or hot conditions.
Look at Leaf pack warranty replacements compared to any other BEV.
Leaf's have nada for TMS. At most while at a DCFC station it will slow the charge rate if the pack is getting too hot.

2. Also strange. Maybe the tech/manual writers need to huddle and talk about what this car has to offer.
Toyota provided a way not to wait for the spring thaw to start your PP in Alaska!

 

PP now comes with universal (meaning all states not just in CARB states) 120 months/150,000 miles hybrid battery warrenty. From a consumer standpoint of view, I would rather have a free replacement battery on my PP before 120 months/150K miles is up by not using the battery heater or cooler than prolong the life of the battery beyond the warranty period by using the battery heater and cooler functions. In any case, I am certain that I will not be driving my PP for 10 years/150K miles. So, experimenting with those functions is completely acceptable to me even if it means shortening the life of the battery.

 

Has Toyota given any details on the battery warranty? I think they've said that range reduction is not covered. Does that mean that if your PP can only get to the end of the driveway that's still okay? Does it require a total failure to trigger the warranty? What happens then - repair or replacement?

Ed

 

So as long as it operates as a Hybrid it's not a deal breaker?
The BEV's I know of have warranty trigger points, such as 30 or 40% reduction in capacity measured in kWh's.
But then the fine print says that a warranty replacement pack does not need to be brand new, it only needs to be 10% better than the one removed. The jerks....
(But then, I really like those jerks! They gave my Bolt a brand new pack with a 6kWh higher capacity and a Start Over on the 8 yr/ 100k mile warranty!)

 

Everything I've heard and read says that battery capacity is normal wear and tear; the battery has to throw a code. The warranty & maintenance manual that came with my Prime says,

 

Fortunately, I have not dealt with it myself with my Prius and PPs yet, and AFAIK, not many owners of regular Prius and Pip, as well as PP, have experienced battery warranty coverage. My understanding is that in order to be even considered for the warranty issue, it has to throw a battery malfunction code I think P0A80 and P3000. Without the code, your chance of getting warranty coverage is slim. Normal capacity reduction is not covered but, I am not sure if Toyota has programmed the code to be thrown if the capacity reaches some preprogrammed low point as @Bill Norton described.

The warranty coverage is for repairs needed to correct the defects. If battery replacement is the only way to correct the defects that would be covered by the warranty. I had my Honda Civic Hybrid hybrid battery replaced under warranty when it failed just a few months before 10 years coverage limit.

Edit: the excerpt below is from the warranty booklet for my 2021 PP for the US model. Canadian warranty may be different.


.

 

Yes, Li-ion batteries will have capacity loss with time and use.
This is normal. For quality EV's with proper TMS for the pack it's usually minimal and predictable.
What's not normal is stating in the warranty that any amount of loss of EV range is considered 'normal wear and tear'.

IF toyota were to someday enter the BEV market , it would need to have a proper Battery Capacity Warranty.

This 'below' will not fly.



BLAH BLAH BLAH

 

Totally agree. They need to guarantee a certain percentage of the original capacity for a certain number of years.
But they don't and that's what we have to live with if we want a Prime. Thankfully, at 59k miles my Prime has the same capacity it did when I got it almost three years ago at 22k miles. But I don't know how long it will stay that way or how quickly it will decline.

 

OK, here is a question. How do other companies selling BEV warrant the capacity loss? Or a better question is how should Toyota warrant the battery capacity loss? Say, if capacity loss of more than 30% in the first 3 years are covered by the warranty. We all know that battery capacity loss is somewhat preventable with good battery care. Then if someone abuses the battery by fully charging the battery in full sun and letting it sit baked resulting in more than 30% capacity loss within the warranty period. He gets a new battery in less than 3 years, whereas those people who took care of the battery by avoiding full charge in hot or cold will see say 10% capacity loss in 3 years. He is not going to get the new battery but inevitably the battery will lose 30% capacity sometime in the future out of the warranty period. I don't think that is going to fly either.

 

One example from Vehicle Warranty | Tesla

 

It's up to the car to protect the battery from idiot users. The PP already prevents overcharge, charging when the battery is too hot / cold, drawing too much power when the battery is cold, etc. Those rules aren't established by Toyota, but by the battery manufacturer (Panasonic?). The safety factors already built-in (e.g. 100% charge on the MID = ~85% on the batteries) are intended to provide adequate protection. If necessary, they could tweak those rules but I don't know if they could do that by a software update or whether they'd have to change a control module.

Jerry, those numbers for the Tesla look good. They seem to hit all the important parameters. By the way, don't forget that Dr. Prius can measure and report the voltage of each cell. Checking this once or twice a year would be a reasonable thing to do. While a total pack failure without warning is possible, a more likely scenario is that one or two cells will slowly fail. Dr. Prius will show you a cell that's starting to drift away from the others. We had a thread here a while back about that, but the OP didn't let us know how things turned out.

 

That is the only solution to the 12V battery going dead. My problem is I live in Sparks, NV and run Comma3 and on occasion a second OBD2 scanner. So I lost track of number of dead batteries and the portable battery jumpers are the only solution. How many times can you call AAA for a jump, so I invested in a battery jumper also. Toyota needs to address this problem and allow the EVSE plugin to also charge both the drive battery and the 12V battery if its plugged in. So when the car is not driven and the 12V goes below some fixed voltage, and if the car is plugged in, it will charge the 12V even if the drive battery is charged to max.The mention of charging every 2 to 3 months from the manual is a joke as the 12V battery would be dead.

 

I agree that a jump box is a requirement for the PP. The combination of covid and my cold winters almost guarantees that it will be needed. But don't get caught in the numbers game of how many thousands of amps the box can provide. We only need to power the computers and a few lights and motors so you could almost use a couple of 6V lantern batteries!

FYI, the manual's comment about charging every 2 to 3 months refers to the traction battery. They say that the 12V battery "may" discharge. Yeah, right!

Ed

 

Especially in cold weather, a 12V battery that is so discharged it will not boot up a Prius has already been damaged and its life expectancy has been drastically shortened.

True, it doesn't take much power to do this 'Boot Up' and any crappy 'Battery Jumper' will do that job.
Once the car is in Ready mode, the HV battery pack powers the DC - DC converter to supply the 12V bus, and car's 12V battery is now getting charged back up.
But the damage has been done...

What a strange thing for a PHEV that is plugged in to an EVSE can still have the 12V battery go dead....
One would think a simple SW update could cure this engineering snafu...