Protect battery when (-30C) -22F

this is why awd prius is getting nimh

 

What is why? Your continued refusal to quote messages you respond to is really becoming a problem. You know how being vague introduces problems in discussion threads. Please include something to indicate what you are referring to!

The reason Toyota selected NiMH for cold climate use is the chemistry can deliver more punch under that particular demand from such a small pack. It is proven robust & affordable, a great use for that application... which has nothing to do with this discussion.

Leaving Prime out for extended periods in extreme cold means battery draw will be restricted and battery charging withheld due to electrical resistance increase when its temperature is below freezing. To overcome that, plug in and use the climate prep. If that option isn't available, just warm up the vehicle prior to driving.

We had to do that over Christmas, when the Prime sat outside in -9F temps. I started the engine to warm up the system. No big deal... aside from the very cold run to the car.

 

i read it was because you can't charge lithium below freezing

 

That's exactly what I mean about vague. What does "it" means and what does "freezing" refer to? A regular poster like yourself should take the time to prevent confusion, not contribute to it.

You make it sounds like recharging the battery-pack isn't possible when the temperature outside is below freezing... which couldn't be further from the truth. Yet, it's easy to see how that impression could be made. A reader could misinterpret the claim as not being able to charge during the winter in northern states.

To be specific, it's the temperature of the battery-pack itself that the software checks for restricting charge acceptance. You plug in, the electric-warmer warms the pack. Some low-power cycling of the pack itself will too. (Lithium will accept electricity when below freezing, it's just very inefficient to do so.) It doesn't take long and a full recharge via plug is well underway. That threshold applies to the recharge from braking too. You can even see that information with an aftermarket reader.

 

they proxy didn't want to spend the money on battery heaters in the awd

 

The only thing that restricts me from charging in -xx F temps is that my L2 charging cable freezes almost solid. Just charged tonight at 10 F. Charging successful (yet lower range) but I have not heard of damage to the battery in those conditions. If there was danger of battery damage I would expect that to be outlined in the owner's manual. I am far more worried that the cheapo charge handle cradle will shatter in painfully cold temps when wrestling it in and out, fighting the almost frozen cable.

The OEM charge cable that comes with the Prime is far more supple in low temps, but I prefer not to use it since I have L2 at home.

All that said, if it really is -22 F outside, EV mode is pretty much a mute issue, since one expects it to start in HV mode at those temps. I am fine with that one month out of 12.

 

This is the data I captured today after 9 hours of sitting outside plugged in. Despite the single-digit cold, it kept the battery-pack several degrees above freezing.



The image is from just a few seconds after starting the system.

 

Do we know exactly what triggers the traction battery heating element inside the pack? (Not climate prep in the cabin)

 

Maybe keeping it hooked up to a (3~4 amp) smart charger (if practical) would keep it a little warmer, and (of course) well topped up on charge.

 

Hybrid Assistant

Here's a full blown sample of what it can show:

 

39° F was all the 'Battery Heater' could muster in 5° F conditions?
That's better than a kick in the pants, but might be described as an ineffective TMS...

Is power output or the charging rate limited when the pack is at 39°?

I read that later Leaf's finally had a battery heating system added to the car.
Before that it had less than an ineffective TMS. It had NO TMS.

I wonder how a proper TMS would handle those temps?
I need to figure out how to get the Torque app PIDS I need for my BEV installed on my tablet.

 

TMS maybe equals Temperature Management System? Help me out lol.

 

too much synergy

 

i think there are various theories

 

TMS = Thermal Management System.

The best PHEV and BEV's have a dedicated TMS that heats and cools the HV battery pack as required while plugged in or powered up.
Ideally it keeps the pack in a happy, healthy temp range with no interaction from the driver.

TMS is there to give the pack a longer life with the least amount of degradation over time.
And only time will tell how well different EV's do in this respect.

 

Some thoughts on cold weather performance of EV batteries.

An internal battery heater design for cold weather charging and the prevention of the damaging effects of lithium plating.
Penn State team devises solution for fast charging of Li-ion batteries at cold temperatures - Green Car Congress
"New research from Idaho National Laboratory..."
EV charging in cold temperatures could pose challenges for drivers
What temperature range can lithium batteries withstand before damage? - Quora

Trying to heat what is basically an uninsulated metal/glass can with electric resistance heating powered in-part or in-full by batteries just doesn't make sense. As seen on youtube, Tesla battery and cabin heaters drawing more power than the stock evse cable could supply and pulling the additional power needed from the battery pack. So you thought you were charging but.. Is there a better way for BEV's? Toyota's fund your hvac repairpersons kids Ivy League education heat pump? Yes it does work for now.

"The best PHEV and BEV's have a dedicated TMS that heats and cools the HV battery pack..." Yes if such a vehicle existed which at this point in time doesn't. I don't see any evidence of Toyota's minimalist air flow/heating pad approach being out performed by those complex and pump dependent "water cooled" packs. If the inside vents are open and there is air flowing past the end of the outlet tube, cooling or heating air from the cabin, will be pulled through the Primes pack . (As reported here on PC ~2 years ago by I don't remember who so feel free to retest the flow) Lose the pump in the other system and you're screwed.
This is what I want to see. Liquid heating or cooling done the right way. 2 phase convective flow with fluid to air heat transfer.

Immersion Cooling - 3M Novec

TMS/BMS Ever here of cell balancing or matching for battery strings? Its need has been known since rechargeables were invented and we have had the electronic designs to do so all most as long (vacuum tube days). I can't think of a single product or system that had it built in. None of my cordless tools, phones, laptops, or ups backups no offgrid/RE solar battery storage systems and none of these hybrid, plugin, or bev battery packs I've seen disassembled.
HEV/EV battery management systems explained simply - Behind the Wheel - Blogs - TI E2E Community


Re: John Kelly's Weber State video of the tear down of the pack.

First 10 minutes. 2 temp sensors on the heating element connected to the BMS. Heating elements are only active when your plugged in. When one of the temp sensors reads 2c or less the heating elements come on and stay on till 5c is reached and then will cycle about this range. 35f to 41f. 2 circuits of 110 watts and 80 watts powered by the 12 volt system via the plugin charger system. 4.56 kwhr per 24 hours? So less than a dollar most places? The 5 stacks of cells each have 3 temp sensors also. The other system when you're driving just blows warm or cool (depending) cabin air into the pack and then it goes outside

I see from Capt. John's videos that his ice also stays above freezing all day and warms up fast too. The new camera looked OK too.

 

>Some HV packs are in somewhat insulated enclosures, the better ones.
I think you are saying 'heat pump' for TMS duties within the pack?
(I believe the i3 has direct freon entering the pack for TMS. There is no freon to coolant heat exchanger. But then how well does that work in extreme cold? )
But what about when it's 5° F, or less, when a heat pump no longer works? You still need a resistance heater as back up.
(Similar to how the Prime handles 'Defrost' when you need heat and dehumidification. The Prime starts the gasser for the heat portion...)

>> You think 'air flow' is an effective TMS system? Leaving air gaps in the cell buildup for air flow vs. direct contact with coolant heated/cooled surfaces?
Also, I'm fairly certain my BEV has a dedicated TMS. It shares the AC compressor with the cabin's evaporator. It has a dedicated coolant heater. Many PHEV's and BEV's use this approach.
Some new offerings from Kia and Hyundai may not have coolant based TMS....
Correct me if I'm wrong.

>>>Vents. Interesting subject!
Is all airflow through the pack exhausted overboard? Even during cold weather while plugged in?
And doesn't this 'sort' of TMS require driver involvement when not plugged in? What if they don't want to have much climate control airflow/temp? The pack just deals???

>>>>BMS is a different subject and all multi cell Li-ion devices have it. It is a 'house cleaning' that takes place after the pack is charged up.
(Some BEV drivers that only use DCFC stations and only to ~80% SOC are at risk of not having a balanced pack.)

>>>>>In summary you are saying that having your HV pack at 35 - 41°F is just fine and the Prime has a thoroughly effective and efficient TMS, correct?