rnlcarlov
Posts: 32
Joined: Wed Apr 13, 2016 8:30 am

Re: Passive cooling ?

Mon Jun 12, 2017 6:27 am

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
Posts: 318
Joined: Wed Jan 28, 2015 1:52 pm
Location: Albuquerque NM

Re: Passive cooling ?

Tue Jun 13, 2017 6:23 pm

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
2014 cool silver ES, acquired new 4/2015
2014 Labrador Black Pearl ES, acquired new 3/2016

rnlcarlov
Posts: 32
Joined: Wed Apr 13, 2016 8:30 am

Re: Passive cooling ?

Thu Jun 15, 2017 11:23 am

Aerowhatt wrote:. "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
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Re: Passive cooling ?

Sat Jun 17, 2017 7:30 am

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: .
"Bear" - 2012 Diamond White Pearl ES with QC - 2/21/2013
Solar-powered since 10/10/2013

"Koorz" - 2012 Cool Silver Metallic ES with QC - 1/5/2015

Driving electric since 2-21-2013.
3 years with the i-MiEV and loving every mile!

rnlcarlov
Posts: 32
Joined: Wed Apr 13, 2016 8:30 am

Re: Passive cooling ?

Sat Jun 17, 2017 7:49 am

PV1 wrote: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
Posts: 318
Joined: Wed Jan 28, 2015 1:52 pm
Location: Albuquerque NM

Re: Passive cooling ?

Thu Jun 22, 2017 11:06 am

PV1 wrote: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
2014 cool silver ES, acquired new 4/2015
2014 Labrador Black Pearl ES, acquired new 3/2016

Aerowhatt
Posts: 318
Joined: Wed Jan 28, 2015 1:52 pm
Location: Albuquerque NM

Re: Passive cooling ?

Thu Jun 22, 2017 11:26 am

rnlcarlov wrote: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
2014 cool silver ES, acquired new 4/2015
2014 Labrador Black Pearl ES, acquired new 3/2016

rnlcarlov
Posts: 32
Joined: Wed Apr 13, 2016 8:30 am

Re: Passive cooling ?

Fri Jun 23, 2017 2:26 am

Aerowhatt wrote:
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
Posts: 318
Joined: Wed Jan 28, 2015 1:52 pm
Location: Albuquerque NM

Re: Passive cooling ?

Fri Jun 23, 2017 10:38 am

rnlcarlov wrote: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 :D

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

Aerowhatt
2014 cool silver ES, acquired new 4/2015
2014 Labrador Black Pearl ES, acquired new 3/2016

Aerowhatt
Posts: 318
Joined: Wed Jan 28, 2015 1:52 pm
Location: Albuquerque NM

Re: Passive cooling ?

Sun Jun 25, 2017 10:12 am

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
2014 cool silver ES, acquired new 4/2015
2014 Labrador Black Pearl ES, acquired new 3/2016

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