Drive battery Thermal Management.

[Trex]

For easy searching and to stop another thread going off topic I wish to discuss the drive battery thermal management here.

First I will bring in some images from Mitsubishi:



And:




And:




So from the images it shows we have a fan or blower in the drive battery case plus a Air Conditioning circuit. ie The drive battery has its own evaporator built in to keep the drive battery cool.

But how do we warm the battery in cold climates?

Well the inlet of the fan or blower could be sourced from the cabin of the PHEV and heating (with electric heater models this could be done while plugged in as well) taken from there. But I am only guessing this at the moment and will do further checking when I can or if others cannot find out how the heating of the drive battery works. Or there could be some sort of themal heating pad for special markets. I would think the battery box also has some thermal insulation properties.

But like I said I am not sure about the heating side.

Not cold enough here where I live for me to have thought about it much.

Regards Trex.

 

[Harald]

But like I said I am not sure about the heating side.
...
Regards Trex.

Thank you "Pictureman".

Might be that the battery is simply used at lower discharge rate, when being cold?
And that it will be on operating temperature soon, after a short time in a limited mode?

Harald

 

[Esparza]

I think there is no heating, only have seen the fan working above 35ºC while driving and 30ºC at CHAdeMO. But my battery has never been below 0ºC. Anyone has seen the fan working at low temperatures? The most symple whay to do it for me will be to use the evaporator as a radiator (heat pump).

 

[AndyH]

I think there is no heating

Some cars in some areas appear to have some sort of battery heater. The 2018 North American model has, but I have no idea yet how it's implemented.

The battery box appears to be sealed, so that rules out using conditioned cabin air. Cold cells under 1C load do warm, but it appears they only gain a couple of degrees - not enough to restore full capability.

2018 NA Owner's Manual (See pages 3-13 through 3-16, 3-40, 9-2, 9-27 [fuse for 'Main drive lithium-ion battery PTC heater])
http://www.catcoinwallets.com/images/posts/EV/2018_PHEV_Owners_Manual.pdf

2018 NA window sticker with note about battery heating ("main battery warming system")
http://www.catcoinwallets.com/images/posts/EV/monroney.pdf

 

[Trex]

I think there is no heating

Some cars in some areas appear to have some sort of battery heater. The 2018 North American model has, but I have no idea yet how it's implemented.

The battery box appears to be sealed, so that rules out using conditioned cabin air. Cold cells under 1C load do warm, but it appears they only gain a couple of degrees - not enough to restore full capability.

2018 NA Owner's Manual (See pages 3-13 through 3-16, 3-40, 9-2, 9-27 [fuse for 'Main drive lithium-ion battery PTC heater])
http://www.catcoinwallets.com/images/posts/EV/2018_PHEV_Owners_Manual.pdf

2018 NA window sticker with note about battery heating ("main battery warming system")
http://www.catcoinwallets.com/images/posts/EV/monroney.pdf

Hi Andy,

Yes looking at it more closely it would appear that the battery box is sealed.

For some markets Mitsi may be just relying on the insulation properties of the battery box. When charging your battery (and thus adding heat) late at night to get off peak tariffs like here it would probably all some of us need.

Regards Trex.

 

[Trex]

Thank you "Pictureman".

Harald

Your welcome Harald.

A picture is worth a thousand words is what I was taught.

 

[NightPHEVer]

I like pictures too - especially in colour. I've mentioned this before on the 'smell of burning' thread, but is one to assume (hey, in my experience never assume anything!) therefore that if the air conditioning was low on gas/oil or not functioning correctly for some other reason, that the batteries would as a result not be sufficiently cooled, possibly resulting in some sort of damage to the batteries? That being the case, shouldn't more emphasis by Mitsubishi be put on 100% efficient operation of the air con rather than just a flashing snowflake symbol?

I get the impression that in 'hot' countries air conditioning is seen as essential, so correctly maintained or repaired if it breaks. Not so in the UK where their are thousands of older cars where the air con has long since expired. Would damage occur to the batteries of a PHEV if they were not sufficiently cooled? Presumably it would, otherwise Mitsubishi wouldn't go to such lengths in the firstplace to ensure that they are cooled. Is does sometimes get to 35oC in the UK.

 

[greendwarf]

I get the impression that in 'hot' countries air conditioning is seen as essential, so correctly maintained or repaired if it breaks. Not so in the UK where their are thousands of older cars where the air con has long since expired. Would damage occur to the batteries of a PHEV if they were not sufficiently cooled? Presumably it would, otherwise Mitsubishi wouldn't go to such lengths in the firstplace to ensure that they are cooled. Is does sometimes get to 35oC in the UK.

Difficult to imagine a scenario in UK where the batteries would be bothered by even 35c. If standing in relentless sun then the batteries are in the shade and if moving then the airflow will be cooling the underneath anyway. I think you would need relentless sun for weeks (heating the ground) combined with hot wind - none of which we get in UK - unlike say, Austrtalia. If we did then I think we would have lots of other more pressing worries than our EV batteries. :lol:

As I recall, the uncooled Leaf battery problems were in the Midwestern US desert states.

 

[AndyH]

I think there is no heating

Some cars in some areas appear to have some sort of battery heater. The 2018 North American model has, but I have no idea yet how it's implemented.

The battery box appears to be sealed, so that rules out using conditioned cabin air. Cold cells under 1C load do warm, but it appears they only gain a couple of degrees - not enough to restore full capability.

2018 NA Owner's Manual (See pages 3-13 through 3-16, 3-40, 9-2, 9-27 [fuse for 'Main drive lithium-ion battery PTC heater])
http://www.catcoinwallets.com/images/posts/EV/2018_PHEV_Owners_Manual.pdf

2018 NA window sticker with note about battery heating ("main battery warming system")
http://www.catcoinwallets.com/images/posts/EV/monroney.pdf

Hi Andy,

Yes looking at it more closely it would appear that the battery box is sealed.

For some markets Mitsi may be just relying on the insulation properties of the battery box. When charging your battery (and thus adding heat) late at night to get off peak tariffs like here it would probably all some of us need.

Regards Trex.

It looks like the only openings in the battery box are the condensate vents under the evaporator inside the battery, and possibly leakage around the emergency disconnect.

I expect the PTC heater is the same tech used by a number of EVs that use PTC heaters for cabin heat. They're small ceramic heaters.

One thing Nissan and other EV makers have learned the hard way is that battery boxes are poor insulators. When we look at the charge and discharge charts you posted, we can see that there isn't enough heat generated by L2 charging or driving to generate more than a few degrees C. Unless one is connected to CHAdeMO, a driver in a cold location will be losing more heat through the battery box than they'd be gaining from charging. Charging is a factor for hot climates, but not much help when it's cold.

it would be interesting to learn which model years and which trim levels have battery heaters.

 

[NightPHEVer]

I get the impression that in 'hot' countries air conditioning is seen as essential, so correctly maintained or repaired if it breaks. Not so in the UK where their are thousands of older cars where the air con has long since expired. Would damage occur to the batteries of a PHEV if they were not sufficiently cooled? Presumably it would, otherwise Mitsubishi wouldn't go to such lengths in the firstplace to ensure that they are cooled. Is does sometimes get to 35oC in the UK.

Difficult to imagine a scenario in UK where the batteries would be bothered by even 35c. If standing in relentless sun then the batteries are in the shade and if moving then the airflow will be cooling the underneath anyway. I think you would need relentless sun for weeks (heating the ground) combined with hot wind - none of which we get in UK - unlike say, Austrtalia. If we did then I think we would have lots of other more pressing worries than our EV batteries. :lol:

As I recall, the uncooled Leaf battery problems were in the Midwestern US desert states.

But isn't quite a lot of heat generated within the batteries themselves when they are being charged by the mains, or the PHEV in 'charge' mode. Especially perhaps in the half-hour 'fast' charge mode option?

 

[Trex]

I get the impression that in 'hot' countries air conditioning is seen as essential, so correctly maintained or repaired if it breaks. Not so in the UK where their are thousands of older cars where the air con has long since expired. Would damage occur to the batteries of a PHEV if they were not sufficiently cooled? Presumably it would, otherwise Mitsubishi wouldn't go to such lengths in the firstplace to ensure that they are cooled. Is does sometimes get to 35oC in the UK.

Difficult to imagine a scenario in UK where the batteries would be bothered by even 35c. If standing in relentless sun then the batteries are in the shade and if moving then the airflow will be cooling the underneath anyway. I think you would need relentless sun for weeks (heating the ground) combined with hot wind - none of which we get in UK - unlike say, Austrtalia. If we did then I think we would have lots of other more pressing worries than our EV batteries. :lol:

This reminds me of when I arrived in London from Heathrow in the 80s and it was early Summer over there. My mate and I wearing jumpers and some people in I think Hyde park had their shirts off sunbathing.

We definitely took our wetsuits on that mainly surfing trip. :lol:

Still had snow on the Pyrenees crossing into Spain. In Summer. :shock:

 

[Trex]

It looks like the only openings in the battery box are the condensate vents under the evaporator inside the battery, and possibly leakage around the emergency disconnect.

And possible leakage around cables and pipes.

I expect the PTC heater is the same tech used by a number of EVs that use PTC heaters for cabin heat. They're small ceramic heaters.

Yep, know what a PTC heater is, had one in my Toyota Prius.

........... battery boxes are poor insulators.

Do not agree with this as a person that has made enclosures and such for insulation reasons both Acoustic and Thermal. Give me enough money and I will build you anything is my motto. Even a battery box with good insulation. I love a challenge. Not sure about Mitsi's battery case though.

Unless one is connected to CHAdeMO, a driver in a cold location will be losing more heat through the battery box than they'd be gaining from charging. Charging is a factor for hot climates, but not much help when it's cold.

Still some speculation here I think. But happy to agree if we can work out what temp is "cold" and how good (or bad) is Mitsi's insulation properties of the case.

It would appear in some markets it is not good enough insulation, that I will agree with, as they have a heater now from what you have shown.

Or they are starting to improve which is always a good thing IMO.

 

[Trex]

I get the impression that in 'hot' countries air conditioning is seen as essential, so correctly maintained or repaired if it breaks. Not so in the UK where their are thousands of older cars where the air con has long since expired. Would damage occur to the batteries of a PHEV if they were not sufficiently cooled? Presumably it would, otherwise Mitsubishi wouldn't go to such lengths in the firstplace to ensure that they are cooled. Is does sometimes get to 35oC in the UK.

Difficult to imagine a scenario in UK where the batteries would be bothered by even 35c. If standing in relentless sun then the batteries are in the shade and if moving then the airflow will be cooling the underneath anyway. I think you would need relentless sun for weeks (heating the ground) combined with hot wind - none of which we get in UK - unlike say, Austrtalia. If we did then I think we would have lots of other more pressing worries than our EV batteries. :lol:

As I recall, the uncooled Leaf battery problems were in the Midwestern US desert states.

But isn't quite a lot of heat generated within the batteries themselves when they are being charged by the mains, or the PHEV in 'charge' mode. Especially perhaps in the half-hour 'fast' charge mode option?

The function of the amount of heat generated (which are the losses in the conversion process that show up as heat) when charging batteries is dependent on how quick you do it is what I was taught.
ie quicker charging more losses more heat and less time to dissipate the heat from those losses I think I remember.

The same in reverse ie discharging.

At mains charging I am only charging at approx .25C so probably not going to get hot IMO. Will check the graphs I bought in over in the other topic.

Do not have a quick charger port on my PHEV so not sure what C it is charging at but will look it up later for you if others do not beat me to it.

Edit How high a SOC does the quick charge take the PHEV in 1/2 an hour.? Save me searching around if someone tells me. 80 or 85% not sure if I remember correctly. :?

 

[anko]

A couple of B5 regens at motorway speed will kick in the battery cooler. You can actually see it in the MMCS dial (if the A/c is off) as a very small yellow line which goes no further that 12:30 position. Maybe not in winter but at least in a Dutch summer.

 

[Trex]

A couple of B5 regens at motorway speed will kick in the battery cooler. You can actually see it in the MMCS dial (if the A/c is off) as a very small yellow line which goes no further that 12:30 position. Maybe not in winter but at least in a Dutch summer.

Yes, good call.

I remember doing those fuel consumption runs years ago and noticing that. B5 at each end of turning around.

I thought I had accidentally turned on the A/c for the cabin which I was trying to avoid. :lol:

 

[Esparza]

Here in Spain its forbidden to sell cars without AC for example. In summer (up to 40ºC) its usual to see the AC compressor working for the battery. But also in winter long trips (300km) at 3ºC ambient sometimes it kicks in for a while as the pack heats in the charge and discharge hysteresis cycle. For me the battery its well isolated, the cells dont touch the case base so its a like a thermo, the only way to transfer heat is through the air inside the battery case and with a stopped fan the natural convection will be minimum. I usually get out of the garage with the cells at 17ºC and even driving at 0ºC the cells are always some degrees hotter at the end of the trip (EV trip). Also charging (slow) it usually maintains or increases the temperature.

 

[AndyH]

A couple of B5 regens at motorway speed will kick in the battery cooler. You can actually see it in the MMCS dial (if the A/c is off) as a very small yellow line which goes no further that 12:30 position. Maybe not in winter but at least in a Dutch summer.

Sure it will! Note, though, that the ambient temp is warm (the pack's starting out warm) and that driving adds more heat. From that starting point, the charge from the strong regen is enough to 'trip the thermostat'. That's not the same as starting with a cold-soaked battery at -20C and warming the battery to +20C.

 

[AndyH]

It looks like the only openings in the battery box are the condensate vents under the evaporator inside the battery, and possibly leakage around the emergency disconnect.

And possible leakage around cables and pipes.

If there are leaks there, they're tiny relative to the amount of air that must move to carry heat in or out.

I expect the PTC heater is the same tech used by a number of EVs that use PTC heaters for cabin heat. They're small ceramic heaters.

Yep, know what a PTC heater is, had one in my Toyota Prius.

The PTC heater could also be a mat. There are other ways to have a heating device with a positive temperature coefficient. It would make sense to use a 'heater slice' in the case with the AC condenser as the system's already configured to push air through.

........... battery boxes are poor insulators.

Do not agree with this as a person that has made enclosures and such for insulation reasons both Acoustic and Thermal. Give me enough money and I will build you anything is my motto. Even a battery box with good insulation. I love a challenge. Not sure about Mitsi's battery case though.

Of course we can build an insulated battery box - but we're not talking about hypothetical generic boxes, right? The tear-down videos and service diagrams for the Outlander show a metal box with no insulation. This is just like other EV and PHEV boxes. Most are designed to conduct heat out of the battery, even when they use forced air like regular hybrids. In the LEAF, conduction is the only form of thermal management. Poor insulators by design, these boxes...

Unless one is connected to CHAdeMO, a driver in a cold location will be losing more heat through the battery box than they'd be gaining from charging. Charging is a factor for hot climates, but not much help when it's cold.

Still some speculation here I think. But happy to agree if we can work out what temp is "cold" and how good (or bad) is Mitsi's insulation properties of the case.

It would appear in some markets it is not good enough insulation, that I will agree with, as they have a heater now from what you have shown.

Or they are starting to improve which is always a good thing IMO.

[/quote]
Not much speculation. But it does rely on the charts you posted that may or may not represent the thermal properties of our battery. Actually, we can see from the charts how a 1C charge only raises the temp of a cell at -20C a couple of degrees C. I don't have enough info to do thermal transfer calcs, but my guess from having worked with different flavors of lithium cells is that on a -20C day and a -20C cold-soaked battery the net heat gain is pretty low but unlikely to be a 10°C move.

I have the opposite problem here - summer heat radiating off tarmac that can reach 125°F/50°C. That makes a battery pretty toasty even before it's asked to do any work. My smart wouldn't let me charge past 90% in the summer with an L2 charge (3.3kW charger) until I fired up the AC for 20 minutes to cool things down. I think batteries would be happy if we took them into the house with us after a drive. :lol:

 

[Esparza]

I think the cells are well isolated. They dont touch the case walls so only way to transfer heat is trough natural convection (fan stopped) by the interal air.
This morning i did a trip with 5ºC ambient temperature, speed about 80kmh and a final consumption of 16.1 kWh (low power demand). The initial temperatures were 17-19 (sleep at garage) and final temps were 19-24. On the afternoon I parked it with 19ºC avg temperature, after 6 hours (ambient 10ºC) the avg temp was 13ºC. For me thats a poor thermal conductivity, and that is good if you have an active cooling system. You can control better the temperature been less dependant of the external temp.

 

[Trex]

I have the opposite problem here - summer heat radiating off tarmac that can reach 125°F/50°C. That makes a battery pretty toasty even before it's asked to do any work. My smart wouldn't let me charge past 90% in the summer with an L2 charge (3.3kW charger) until I fired up the AC for 20 minutes to cool things down. I think batteries would be happy if we took them into the house with us after a drive. :lol:

:lol:

Yep same here about the heat.

Does the Smart not start the A/C in the battery case for charging?