Passive cooling ?

[PV1]

I don't think lithium batteries are supposed to vent unless on the brink of rupturing.

I get more of a off-gassing plastic smell, likely caused by stale air in the pack 99% of the time.

Have you checked your coolant levels (both front and back reservoirs)?

 

[nhhecker]

So I left the damper closed (i.e., in the stock configuration) for the past few days and the smell's gone away. So whatever it is, it must be coming from the battery pack. It goes away after a minute of driving with the windows down, so not a big deal, but maybe a DPDT switch is the way to go with one side being car-controlled and the other side being a manual override to force open the damper... or do just like PV1 said and go all manual, although I'd hate to forget to open the damper while on a DCQC.

PV1, are you talking about a the smell of plasticizer? It seems like a different smell to my nose, but then again it's been a minute since I've smelled plasticizer. I'll have to smell again and see if I can more closely identify the smell. Coolant levels are at the full mark when I checked last weekend, and haven't budged since I bought the car. What makes you ask?

kiev, I do have CanIon (what an amazing program) but I haven't noticed any weak cells -- I'll keep an eye out. I haven't done any CHAdeMO charging in almost a year now, maybe I need to get over to one and do some experimenting.

Thanks both for the info, at least I know I'm not totally crazy. (Well, there's still time... )
Nick

 

[PV1]

Just ruling out a leaking heater core, which you've already done by closing the battery damper.

It might be plasticizer. Even my dash vents will give off the smell on hot days.

 

[kiev]

You're right, the cells shouldn't normally be venting, but under high current situations such as chademo dcqc, or wide-open acceleration, a weak or defective cell can heat up the electrolyte causing a rise in pressure that would be released thru the one-way relief valve in the top of the cell.

A massive overpressure event (four letter f-word that rhymes with hire) would rupture the burst disk on the side of the cell.

 

[mdbuilder]

Slightly venting or leaking lithium cells I've experienced smell sort of sweet, not really foul or burnt at all. I would assume I-Miev cells would be similar.

 

[Aerowhatt]

It's battery cooling season again. I have kind of a unique home parking situation that I would like to take better advantage of. 97F outside today and summer is just getting started. I've found even though my garage stays under 80F no matter how hot the outside temperature is and it starts the mornings in the low 70's inside the garage. My batteries could be cooler in the morning to start the day than they are (it would make me happy if they were ). I did a couple of tests running the ambient air through the pack with the cabin blower and the battery duct fully open, dash selector set to all floor position. Sure enough I can charge overnight and start the day with the pack ~11F cooler!! Perhaps more importantly, less variation in cell temperatures than I get with just the intended conduction cooling of a closed pack. For testing, I got the car charge started late at night and turn the key on to run the cabin blower. Not practical long term, so the question is how to run air through the pack all night more practically? This could also be helpful to those parked outdoors if such a system would blow air based on the air temperature. Like a heating thermostat . . . when the ambient air gets cool enough a blower pulls/pushes it through the pack when ambient temperature rises the the thermostat stops the airflow.

Some of the hottest places have very cool nights which could be used to much better advantage, than without circulating air through the pack! Here in the high desert, summer lows can be 35 to 50 degrees F lower than the afternoon high. Wondering if anyone has explored this, or has a bright idea on the best way to accomplish it, or is interested in helping brainstorm one?

Aerowhatt

 

[rnlcarlov]

For testing, I got the car charge started late at night and turn the key on to run the cabin blower. Not practical long term, so the question is how to run air through the pack all night more practically? This could also be helpful to those parked outdoors if such a system would blow air based on the air temperature.

I personally avoid that method ever since I tried it once and nearly emptied my 12V battery. Turns out it's only charged during "ready" mode.

About other solutions, well I posted in another thread about portable chademo chargers which can work from single-phase power. We can regulate their output to low Amps and as long as we've got cells above 20ºC the car should continuously blow air into the pack.
Of course, these devices aren't the cheapest thing around, but since they can also be used to charge the car faster (up to 8kW), it's a 2 in 1.

 

[Aerowhatt]

I personally avoid that method ever since I tried it once and nearly emptied my 12V battery. Turns out it's only charged during "ready" mode.

About other solutions, well I posted in another thread about portable chademo chargers which can work from single-phase power. We can regulate their output to low Amps and as long as we've got cells above 20ºC the car should continuously blow air into the pack.
Of course, these devices aren't the cheapest thing around, but since they can also be used to charge the car faster (up to 8kW), it's a 2 in 1.

The car also charges the 12 volt system from the DC to DC during active charging from L1 or L2. But it's not a practical solution long term because once the charge ends (traction pack full) the 12V battery begins to run down which would only take two or three hours running the cabin blower. Ideally I want to run the battery exhaust blower (it does a better job moving air through the pack) while charging L1 or L2 and set it up for the fan to stop when the car turns off the EVSE. Simple enough really, but not straight forward either.

Not really interested in sinking big money in to a portable chademo. I have no need for charging faster than L2. On occasion that I did, much cheaper to use a public unit for $8 to $10 a whack. Thanks for the thought, but it's not the reasonable solution that I'm seeking.

Aerowhatt

 

[rnlcarlov]

Not really interested in sinking big money in to a portable chademo. I have no need for charging faster than L2. On occasion that I did, much cheaper to use a public unit for $8 to $10 a whack. Thanks for the thought, but it's not the reasonable solution that I'm seeking.

Aerowhatt

$8 to $10? Jesus Christ, that's *expellative* expensive. That definitely kills long trips using EVs.

 

[wmcbrine]

$8 to $10? Jesus Christ, that's *expellative* expensive. That definitely kills long trips using EVs.

Well, it isn't always that much. (EVgo can cost that, if you don't get one of the higher-level plans.) But I believe his point was just, that even at those rates, it would take a long time for the portable CHAdeMO unit to pay off (~400-500 sessions), if you look at that as the alternative.

For myself, I don't quite see it that way, since the nearest public CHAdeMO is a long ways from here, so I can't just make a quick trip there to charge. Instead, I think about how it's almost half what I paid for my car, and that puts me off.

 

[rnlcarlov]

Of course I wouldn't reccomend a portable Chademo charger as an alternative to regular Chademo public stations. But in many countries the Chademo coverage is insufficient for the range of the triplets, so there's that. I'm still on the "wait and see" phase, since payment on quick-charge station is scheduled to start in my country soon. Depeding on the price we have to pay, a portable Chademo could result in some savings. Combining that with cooling during "slower charging", faster charging on 7 or 22kw AC charging stations and adjustable output (for charging in some old places where 14A trips the breaker, it becomes rather tempting for me.

You got your car for 7k? :shock: Sounds like a nice price (depending on the remaining Ah, of course)

 

[Aerowhatt]

So I've been looking at the main battery exhaust blower and wiring, etc, in the shop manual. Looks doable to add in a relay to run the blower powered by, perhaps the onboard charger 12 volt relay activation. That way when the charger shuts down (and the DC to DC shuts down too ) so does the fan. Also it needs to be installed so that it doesn't interfere with normal operation of that blower, QCDC etc. Or trip any error traps. So next is to look at it from every angle and hopefully catch any trouble spots before they are actually encountered. "dumb" systems are so much easier to mod than "smart" ones. At first blush it looks totally doable and could even include an ambient air temp function so it only runs when the ambient air is cool enough to make a reasonable difference.

Aerowhatt

 

[rnlcarlov]

. "dumb" systems are so much easier to mod than "smart" ones.

I hear ya. Can you imagine if we could do the same to stuff to EV cars as people do in electric motorcycles? Custom battery packs, chargers, et cetera.....

 

[PV1]

The thing to watch for when trying to run the pack fan is that the cabin HVAC has the battery damper flipped and the vents set to the floor. Otherwise, you're not going to get much airflow through the pack.

Although not really passive cooling, I have removed the servo that controls the battery air damper and just leave it set to the battery full time. I never use the floor vents (when I do, it's easy to reach down and flip the lever), so anytime I want to send air through the battery, conditioned or not, I simply set the airflow to the floor. These last few days, I've been splitting the A/C, 75% to the battery, 25% to me.

Sometimes, in the winter, I can do double duty (warm the battery and cool the cabin) by cracking a window open, turning on the recirculator, and send all air to the battery. This draws the warm air in the cabin through the system and into the battery, which also pulls cool outside air into the cabin. This is what I do on those 40F days when the inside of the car is 80+. Free heat nets increased regen with a warmer pack :ugeek: .

 

[rnlcarlov]

The thing to watch for when trying to run the pack fan is that the cabin HVAC has the battery damper flipped and the vents set to the floor. Otherwise, you're not going to get much airflow through the pack.

Although not really passive cooling, I have removed the servo that controls the battery air damper and just leave it set to the battery full time. I never use the floor vents (when I do, it's easy to reach down and flip the lever), so anytime I want to send air through the battery, conditioned or not, I simply set the airflow to the floor.

That's my setup, too. I'm not sure if I said this here already, but in my case I just connected the car to a public Chademo charger, unplugged the power to the servo while the system was sending air to the pack, and now it's locked in the battery position. If I plug the servo again it should go back to its position. It's not a solution so flexible, but I don't use the foot vents, either. Actually, once I turn the AC to the battery, I always get some cold air on my feet. More than I would like, too. The vents are not 100% sealed.

 

[Aerowhatt]

The thing to watch for when trying to run the pack fan is that the cabin HVAC has the battery damper flipped and the vents set to the floor. Otherwise, you're not going to get much airflow through the pack.

A good reminder. I assumed anyone deep into this thread would remember that, but likely a reckless assumption

Aerowhatt

 

[Aerowhatt]

Actually, once I turn the AC to the battery, I always get some cold air on my feet. More than I would like, too. The vents are not 100% sealed.

That's interesting, On my car it is a very good seal. No discernible airflow out of the floor vents when in Battery vent mode.

It's hitting 105 F here today and I can keep the hottest cell under 91F if I work at it. Frankly though, the temperature management system is less than stellar. If you let it get ahead of you, it just doesn't move enough BTU's fast enough to play catch up. That's partly why I want to find a practical automatic way to cool (as much as the environment allows) for hours on end at night and while charging at night. Starting the driving day as cool as possible is critical to success in holding down the temps overall.

The cabin fan cools it's motor with the air that it is moving (like most blowers). So the higher it is set to run air through the restricted duct to the battery the more heat it adds to ambient air temp before sending it to the pack. It produces significant heat with all of that back pressure! In that sense pulling ambient air through makes more sense. However the battery exhaust blower is not well suited to the task for a number of reasons. :roll:

Aerowhatt

 

[rnlcarlov]

That's interesting, On my car it is a very good seal. No discernible airflow out of the floor vents when in Battery vent mode.

It's hitting 105 F here today and I can keep the hottest cell under 91F if I work at it. Frankly though, the temperature management system is less than stellar. If you let it get ahead of you, it just doesn't move enough BTU's fast enough to play catch up. That's partly why I want to find a practical automatic way to cool (as much as the environment allows) for hours on end at night and while charging at night. Starting the driving day as cool as possible is critical to success in holding down the temps overall.

The cabin fan cools it's motor with the air that it is moving (like most blowers). So the higher it is set to run air through the restricted duct to the battery the more heat it adds to ambient air temp before sending it to the pack. It produces significant heat with all of that back pressure! In that sense pulling ambient air through makes more sense. However the battery exhaust blower is not well suited to the task for a number of reasons. :roll:

If you say the 12V battery is charged during L1 or L2 charging, then a possible solution would be to leave the cabin blower on during charging and have an EVSE with ajustable output (6A to 14A, for example). If you have a general idea of how much %/hour it charges at each speed, you can set it up so that it finishes charging right when you need it, avoiding running down the 12V battery.
Of course this only works is the ambient temperature is low enough at night.

 

[Aerowhatt]

If you say the 12V battery is charged during L1 or L2 charging, then a possible solution would be to leave the cabin blower on during charging and have an EVSE with ajustable output (6A to 14A, for example). If you have a general idea of how much %/hour it charges at each speed, you can set it up so that it finishes charging right when you need it, avoiding running down the 12V battery.
Of course this only works is the ambient temperature is low enough at night.

I thought that would be a good idea too. A few nights ago I did set my wife's car up to have air circulation thru the pack while L1 charging. It didn't work out well though. it appears that heat given off during charging is significant whether the Charge rate is L1 or L2. One of the winter time strategy threads touches on this, as people having better luck keeping the battery warmer charging on L1 than when charging on L2. Basically, active ventilation with ambient air around 10 F cooler than battery temps will only mitigate cell temperature increases during charging, but not reduce those temperatures much, if at all. So the shorter charge time and all night active ventilation (at medium fan speed) has the largest impact. Higher fan speeds cool less well due to the fan motor waste heat, fighting the additional back pressure on it at higher speeds.

So the bottom line seems to be that L2 charging and ventilating the battery pack continuously as long as the Ambient temperature is lower than the average cell temperature. During charging it holds off further cell temperature increase and before or after charging it makes a significant difference in the morning temperature (9 F to 11 F) of the pack compared with doing nothing at all . . . so far.

I have rigged up a 12 volt 7 amp battery charger that I had as surplus to supplement the 12 volt system overnight (thru the accessory power port) so that I can run my wife's fan all night tonight and see how it compares to previous data from her daily parking and driving. She is moderately averse to taking the time and energy to do what I do with my car while driving, etc. Using AC to the pack etc. The AC to the pack makes a huge difference in accumulation of heat in the pack throughout the day.

No Active intervention:
Her car will arrive home with 102 F highest cell with ~99 F average for the whole pack. Then after sitting in a 77 F average temperature garage for 13 hours and charging around 4 bars (L2) during that time. By morning departure time, the Pack will have a highest cell temp of 97 F and a whole pack average of 95 F

With active intervention: Running AC through the pack all day whenever driving. Sharing with the cabin as much as needed to stay nice and comfortable! Then active cooling as best possible, with ambient air when home in the garage and 7 to 13 bars of L2 charging during that time. I am able to keep the peak highest cell temperature at or below 91 F and morning departure pack temperature of 78 F to 82 F

A striking difference IMO. The key is to make it simpler and more automatic to achieve!

Aerowhatt

 

[Aerowhatt]

So, obviously leaving the key on all night every night and supplementing the 12 volt system with a battery charger is not a long term solution but the data from doing it leads to one.

I did that all night ventilation on my wife’s car and it had an uncharacteristically long charge cycle needing 12 bars replaced instead of the usual 4 or 5! So a longer charging cycle working against the ambient air pack cooling, and a hotter start than the previous night. Still the morning departure temperature for the battery was 87 F, down from the previous 95 F without intervention and only a 4 bar recharge. The cabin blower can work well for this if it is run at mid speed and no higher. Doing so with the key on isn’t practical since it runs a bunch of other systems (unnecessary wear and tear) pulling more than 7 amps total. The cabin blower itself is only pulling ~2.25 amps at 5.5 Volts to run at mid speed.

The solution appears to be to provide a separate power supply between 5 and 6 volts to the blower itself. This leaves the key off, saving power and wear and tear on other electronics. It also lets the charge be timed etc. (having the key on prevents timer delayed charging from starting and all remote function from being available). So next is to come up with a suitable power supply.

So, about half of the battle against high cell temps can be won without any driving habit changing. The other half requires driver attention and a bit of a relearn of how to use the AC to the best advantage for both the battery and passengers. Very broadly, I just the run the AC on mid fan speed (temperature set to COLD) all day in this summer heat. To control cabin comfort, instead of changing the fan speed (or temperature setting), I change the duct selector instead. More to the dash if feeling warm. More to the “floor” if feeling too cool. This seems to work very well and be very easy to manage. Of course if one is getting into a 130 F cabin from being parked in the sun for an hour or more, requires more drastic measures for a short time.

Aerowhatt